gdz.top
Номер 21.4, страница 128 - гдз по физике 8-11 класс учебник, задачник Гельфгат, Генденштейн
Авторы: Гельфгат И. М., Генденштейн Л. Э., Кирик Л. А.
Тип: Учебник, задачник
Издательство: Илекса
Год издания: 2005 - 2026
Цвет обложки: синий мужчина в красном, летит на черном шаре
ISBN: 978-5-89237-332-6
Популярные ГДЗ в 8 классе
Задачи. Теория относительности и атомная физика. 21. Пространство, время, движение в теории относительности - номер 21.4, страница 128.
App\Models\Task {#1030 // resources/views/models/task/default.blade.php #connection: "mysql" #table: "tasks" #primaryKey: "id" #keyType: "int" +incrementing: true #with: [] #withCount: [] +preventsLazyLoading: false #perPage: 15 +exists: true +wasRecentlyCreated: false #escapeWhenCastingToString: false #attributes: array:24 [ "id" => 1288789 "created_at" => "2026-04-10 13:58:26" "updated_at" => null "field_page_start" => "128" "field_page_end" => null "field_url" => "/8-klass/fizika/ileksa-gelfgat-uchebnik/21-4" "field_display_title" => "21.4" "field_outside_task" => null "field_task_type" => Illuminate\Database\Eloquent\Collection {#1037 #items: array:1 [ 0 => App\Models\Term {#1036 #connection: "mysql" #table: "terms" #primaryKey: "id" #keyType: "int" +incrementing: false #with: [] #withCount: [] +preventsLazyLoading: false #perPage: 15 +exists: true +wasRecentlyCreated: false #escapeWhenCastingToString: false #attributes: array:6 [ "id" => 26 "created_at" => "2026-04-10 13:58:26" "updated_at" => null "name" => "номер" "field_cases" => array:6 [ "field_accusative_case" => "номер" "field_creative_case" => "номером" "field_dative_case" => "номеру" "field_genitive_case" => "номера" "field_nominative_case" => "номер" "field_prepositional_case" => "номере" ] "field_short_name" => "№" ] #original: array:6 [ "id" => 26 "created_at" => "2026-04-10 13:58:26" "updated_at" => null "name" => "номер" "field_cases" => array:6 [ "field_accusative_case" => "номер" "field_creative_case" => "номером" "field_dative_case" => "номеру" "field_genitive_case" => "номера" "field_nominative_case" => "номер" "field_prepositional_case" => "номере" ] "field_short_name" => "№" ] #changes: [] #casts: [] #classCastCache: [] #attributeCastCache: [] #dateFormat: null #appends: [] #dispatchesEvents: [] #observables: [] #relations: [] #touches: [] +timestamps: true +usesUniqueIds: false #hidden: [] #visible: [] #fillable: [] #guarded: array:1 [ 0 => "*" ] } ] #escapeWhenCastingToString: false } "field_metatags_title" => null "field_metatags_description" => null "field_h1" => null "field_description_top" => null "field_description_bottom" => null "field_match" => null "breadcrumbs" => [] "edition_groups" => Illuminate\Database\Eloquent\Collection {#1035 #items: [] #escapeWhenCastingToString: false } "top_parent_branch" => Illuminate\Database\Eloquent\Collection {#1076 #items: array:1 [ 0 => App\Models\Branch {#1034 #connection: "mysql" #table: "branches" #primaryKey: "id" #keyType: "int" +incrementing: true #with: [] #withCount: [] +preventsLazyLoading: false #perPage: 15 +exists: true +wasRecentlyCreated: false #escapeWhenCastingToString: false #attributes: array:24 [ "id" => 1287866 "created_at" => "2026-04-10 13:58:26" "updated_at" => null "field_display_title" => "Задачи" "field_branch_order" => null "field_url" => null "field_branch_type" => Illuminate\Database\Eloquent\Collection {#1039 #items: [] #escapeWhenCastingToString: false } "field_page_start" => "5" "field_branch_display" => "0" "field_branch_expanded" => "0" "field_display_branch_in_title" => "1" "field_display_task_interval" => "0" "field_display_branch_page" => "1" "field_branch_title_in_content" => "0" "field_navigation_title" => null "field_metatags_title" => null "field_metatags_description" => null "field_h1" => null "field_description_top" => null "field_description_bottom" => null "field_branch_cover" => [] "field_branch_covers" => [] "book" => Illuminate\Database\Eloquent\Collection {#1038 #items: array:1 [ 0 => App\Models\Book {#1040 #connection: "mysql" #table: "books" #primaryKey: "id" #keyType: "int" +incrementing: false #with: [] #withCount: [] +preventsLazyLoading: false #perPage: 15 +exists: true +wasRecentlyCreated: false #escapeWhenCastingToString: false #attributes: array:50 [ "id" => 5401 "created_at" => "2026-04-10 13:58:26" "updated_at" => null "field_tree_default_status" => "tasks" "field_pages_status" => null "field_subject" => Illuminate\Database\Eloquent\Collection {#1041 …2} "field_class" => Illuminate\Database\Eloquent\Collection {#1043 …2} "field_publisher" => Illuminate\Database\Eloquent\Collection {#1048 …2} "field_author" => Illuminate\Database\Eloquent\Collection {#1050 …2} "field_author_foreign" => Illuminate\Database\Eloquent\Collection {#1054 …2} "field_book_type" => Illuminate\Database\Eloquent\Collection {#1055 …2} "field_country" => Illuminate\Database\Eloquent\Collection {#1057 …2} "field_city" => Illuminate\Database\Eloquent\Collection {#1059 …2} "field_series" => Illuminate\Database\Eloquent\Collection {#1061 …2} "field_umk" => Illuminate\Database\Eloquent\Collection {#1062 …2} "field_level_of_education" => Illuminate\Database\Eloquent\Collection {#1063 …2} "field_standart_of_education" => Illuminate\Database\Eloquent\Collection {#1064 …2} "field_publication_number" => "6" "field_publication_type" => Illuminate\Database\Eloquent\Collection {#1065 …2} "field_under_the_edition" => Illuminate\Database\Eloquent\Collection {#1067 …2} "field_under_the_edition_degree" => null "field_cover_description" => "мужчина в красном, летит на черном шаре" "field_publication_year" => "2005" "field_publication_year_until" => null "field_part" => "" "field_part_writing" => "" "field_second_foreign_language" => null "field_for_whom" => "Учебное издание" "field_allowed" => null "field_reserve_field" => null "field_link_to_source" => null "field_tasks_count" => "1001" "field_priority" => null "field_default_folder" => "/fizika_08/gelfgat-u/" "field_isbn" => "978-5-89237-332-6" "field_cover" => array:1 [ …1] "field_cover_alts" => array:1 [ …1] "field_covers" => array:1 [ …1] "field_popular_book" => "0" "field_recommended_books" => Illuminate\Database\Eloquent\Collection {#1068 …2} "field_new_book" => Illuminate\Database\Eloquent\Collection {#1069 …2} "field_old_book" => Illuminate\Database\Eloquent\Collection {#1070 …2} "field_url" => "/8-klass/fizika/ileksa-gelfgat-uchebnik" "field_cover_color" => Illuminate\Database\Eloquent\Collection {#1071 …2} "field_metatags_title" => null "field_metatags_description" => null "field_h1" => null "field_description_top" => null "field_description_bottom" => null "breadcrumbs" => array:3 [ …3] ] #original: array:50 [ "id" => 5401 "created_at" => "2026-04-10 13:58:26" "updated_at" => null "field_tree_default_status" => "tasks" "field_pages_status" => null "field_subject" => Illuminate\Database\Eloquent\Collection {#1041 …2} "field_class" => Illuminate\Database\Eloquent\Collection {#1043 …2} "field_publisher" => Illuminate\Database\Eloquent\Collection {#1048 …2} "field_author" => Illuminate\Database\Eloquent\Collection {#1050 …2} "field_author_foreign" => Illuminate\Database\Eloquent\Collection {#1054 …2} "field_book_type" => Illuminate\Database\Eloquent\Collection {#1055 …2} "field_country" => Illuminate\Database\Eloquent\Collection {#1057 …2} "field_city" => Illuminate\Database\Eloquent\Collection {#1059 …2} "field_series" => Illuminate\Database\Eloquent\Collection {#1061 …2} "field_umk" => Illuminate\Database\Eloquent\Collection {#1062 …2} "field_level_of_education" => Illuminate\Database\Eloquent\Collection {#1063 …2} "field_standart_of_education" => Illuminate\Database\Eloquent\Collection {#1064 …2} "field_publication_number" => "6" "field_publication_type" => Illuminate\Database\Eloquent\Collection {#1065 …2} "field_under_the_edition" => Illuminate\Database\Eloquent\Collection {#1067 …2} "field_under_the_edition_degree" => null "field_cover_description" => "мужчина в красном, летит на черном шаре" "field_publication_year" => "2005" "field_publication_year_until" => null "field_part" => "" "field_part_writing" => "" "field_second_foreign_language" => null "field_for_whom" => "Учебное издание" "field_allowed" => null "field_reserve_field" => null "field_link_to_source" => null "field_tasks_count" => "1001" "field_priority" => null "field_default_folder" => "/fizika_08/gelfgat-u/" "field_isbn" => "978-5-89237-332-6" "field_cover" => array:1 [ …1] "field_cover_alts" => array:1 [ …1] "field_covers" => array:1 [ …1] "field_popular_book" => "0" "field_recommended_books" => Illuminate\Database\Eloquent\Collection {#1068 …2} "field_new_book" => Illuminate\Database\Eloquent\Collection {#1069 …2} "field_old_book" => Illuminate\Database\Eloquent\Collection {#1070 …2} "field_url" => "/8-klass/fizika/ileksa-gelfgat-uchebnik" "field_cover_color" => Illuminate\Database\Eloquent\Collection {#1071 …2} "field_metatags_title" => null "field_metatags_description" => null "field_h1" => null "field_description_top" => null "field_description_bottom" => null "breadcrumbs" => array:3 [ …3] ] #changes: [] #casts: [] #classCastCache: [] #attributeCastCache: [] #dateFormat: null #appends: [] #dispatchesEvents: [] #observables: [] #relations: [] #touches: [] +timestamps: true +usesUniqueIds: false #hidden: [] #visible: [] #fillable: [] #guarded: array:1 [ 0 => "*" ] } ] #escapeWhenCastingToString: false } "branch_parent" => Illuminate\Database\Eloquent\Collection {#1073 #items: [] #escapeWhenCastingToString: false } ] #original: array:24 [ "id" => 1287866 "created_at" => "2026-04-10 13:58:26" "updated_at" => null "field_display_title" => "Задачи" "field_branch_order" => null "field_url" => null "field_branch_type" => Illuminate\Database\Eloquent\Collection {#1039} "field_page_start" => "5" "field_branch_display" => "0" "field_branch_expanded" => "0" "field_display_branch_in_title" => "1" "field_display_task_interval" => "0" "field_display_branch_page" => "1" "field_branch_title_in_content" => "0" "field_navigation_title" => null "field_metatags_title" => null "field_metatags_description" => null "field_h1" => null "field_description_top" => null "field_description_bottom" => null "field_branch_cover" => [] "field_branch_covers" => [] "book" => Illuminate\Database\Eloquent\Collection {#1038} "branch_parent" => Illuminate\Database\Eloquent\Collection {#1073} ] #changes: [] #casts: [] #classCastCache: [] #attributeCastCache: [] #dateFormat: null #appends: [] #dispatchesEvents: [] #observables: [] #relations: [] #touches: [] +timestamps: true +usesUniqueIds: false #hidden: [] #visible: [] #fillable: [] #guarded: array:1 [ 0 => "*" ] } ] #escapeWhenCastingToString: false } "parent_branches" => Illuminate\Database\Eloquent\Collection {#1113 #items: array:3 [ 0 => App\Models\Branch {#1123 #connection: "mysql" #table: "branches" #primaryKey: "id" #keyType: "int" +incrementing: true #with: [] #withCount: [] +preventsLazyLoading: false #perPage: 15 +exists: true +wasRecentlyCreated: false #escapeWhenCastingToString: false #attributes: array:24 [ "id" => 1287866 "created_at" => "2026-04-10 13:58:26" "updated_at" => null "field_display_title" => "Задачи" "field_branch_order" => null "field_url" => null "field_branch_type" => Illuminate\Database\Eloquent\Collection {#1124 #items: [] #escapeWhenCastingToString: false } "field_page_start" => "5" "field_branch_display" => "0" "field_branch_expanded" => "0" "field_display_branch_in_title" => "1" "field_display_task_interval" => "0" "field_display_branch_page" => "1" "field_branch_title_in_content" => "0" "field_navigation_title" => null "field_metatags_title" => null "field_metatags_description" => null "field_h1" => null "field_description_top" => null "field_description_bottom" => null "field_branch_cover" => [] "field_branch_covers" => [] "book" => Illuminate\Database\Eloquent\Collection {#1160 #items: array:1 [ 0 => App\Models\Book {#1125 #connection: "mysql" #table: "books" #primaryKey: "id" #keyType: "int" +incrementing: false #with: [] #withCount: [] +preventsLazyLoading: false #perPage: 15 +exists: true +wasRecentlyCreated: false #escapeWhenCastingToString: false #attributes: array:50 [ "id" => 5401 "created_at" => "2026-04-10 13:58:26" "updated_at" => null "field_tree_default_status" => "tasks" "field_pages_status" => null "field_subject" => Illuminate\Database\Eloquent\Collection {#1127 #items: array:1 [ 0 => App\Models\Term {#1126 #connection: "mysql" #table: "terms" #primaryKey: "id" #keyType: "int" +incrementing: false #with: [] #withCount: [] +preventsLazyLoading: false #perPage: 15 +exists: true +wasRecentlyCreated: false #escapeWhenCastingToString: false #attributes: array:10 [ "id" => 6493 "created_at" => "2026-04-10 13:58:26" "updated_at" => null "name" => "Физика" "field_abbreviated_name" => null "field_cases" => array:6 [ …6] "field_foreign_lang_name" => null "field_short_name" => null "field_subject_type" => "technical_subject" "field_translit" => "fizika" ] #original: array:10 [ "id" => 6493 "created_at" => "2026-04-10 13:58:26" "updated_at" => null "name" => "Физика" "field_abbreviated_name" => null "field_cases" => array:6 [ …6] "field_foreign_lang_name" => null "field_short_name" => null "field_subject_type" => "technical_subject" "field_translit" => "fizika" ] #changes: [] #casts: [] #classCastCache: [] #attributeCastCache: [] #dateFormat: null #appends: [] #dispatchesEvents: [] #observables: [] #relations: [] #touches: [] +timestamps: true +usesUniqueIds: false #hidden: [] #visible: [] #fillable: [] #guarded: array:1 [ 0 => "*" ] } ] #escapeWhenCastingToString: false } "field_class" => Illuminate\Database\Eloquent\Collection {#1128 #items: array:4 [ 0 => App\Models\Term {#1129 #connection: "mysql" #table: "terms" #primaryKey: "id" #keyType: "int" +incrementing: false #with: [] #withCount: [] +preventsLazyLoading: false #perPage: 15 +exists: true +wasRecentlyCreated: false #escapeWhenCastingToString: false #attributes: array:6 [ "id" => 5457 "created_at" => "2026-04-10 13:58:26" "updated_at" => null "name" => "8" "field_cases" => array:6 [ …6] "field_translit" => "vosmoj" ] #original: array:6 [ "id" => 5457 "created_at" => "2026-04-10 13:58:26" "updated_at" => null "name" => "8" "field_cases" => array:6 [ …6] "field_translit" => "vosmoj" ] #changes: [] #casts: [] #classCastCache: [] #attributeCastCache: [] #dateFormat: null #appends: [] #dispatchesEvents: [] #observables: [] #relations: [] #touches: [] +timestamps: true +usesUniqueIds: false #hidden: [] #visible: [] #fillable: [] #guarded: array:1 [ 0 => "*" ] } 1 => App\Models\Term {#1130 #connection: "mysql" #table: "terms" #primaryKey: "id" #keyType: "int" +incrementing: false #with: [] #withCount: [] +preventsLazyLoading: false #perPage: 15 +exists: true +wasRecentlyCreated: false #escapeWhenCastingToString: false #attributes: array:6 [ "id" => 5458 "created_at" => "2026-04-10 13:58:26" "updated_at" => null "name" => "9" "field_cases" => array:6 [ …6] "field_translit" => "devjatyj" ] #original: array:6 [ "id" => 5458 "created_at" => "2026-04-10 13:58:26" "updated_at" => null "name" => "9" "field_cases" => array:6 [ …6] "field_translit" => "devjatyj" ] #changes: [] #casts: [] #classCastCache: [] #attributeCastCache: [] #dateFormat: null #appends: [] #dispatchesEvents: [] #observables: [] #relations: [] #touches: [] +timestamps: true +usesUniqueIds: false #hidden: [] #visible: [] #fillable: [] #guarded: array:1 [ 0 => "*" ] } 2 => App\Models\Term {#1131 #connection: "mysql" #table: "terms" #primaryKey: "id" #keyType: "int" +incrementing: false #with: [] #withCount: [] +preventsLazyLoading: false #perPage: 15 +exists: true +wasRecentlyCreated: false #escapeWhenCastingToString: false #attributes: array:6 [ "id" => 5459 "created_at" => "2026-04-10 13:58:26" "updated_at" => null "name" => "10" "field_cases" => array:6 [ …6] "field_translit" => "desjatyj" ] #original: array:6 [ "id" => 5459 "created_at" => "2026-04-10 13:58:26" "updated_at" => null "name" => "10" "field_cases" => array:6 [ …6] "field_translit" => "desjatyj" ] #changes: [] #casts: [] #classCastCache: [] #attributeCastCache: [] #dateFormat: null #appends: [] #dispatchesEvents: [] #observables: [] #relations: [] #touches: [] +timestamps: true +usesUniqueIds: false #hidden: [] #visible: [] #fillable: [] #guarded: array:1 [ 0 => "*" ] } 3 => App\Models\Term {#1132 #connection: "mysql" #table: "terms" #primaryKey: "id" #keyType: "int" +incrementing: false #with: [] #withCount: [] +preventsLazyLoading: false #perPage: 15 +exists: true +wasRecentlyCreated: false #escapeWhenCastingToString: false #attributes: array:6 [ "id" => 5460 "created_at" => "2026-04-10 13:58:26" "updated_at" => null "name" => "11" "field_cases" => array:6 [ …6] "field_translit" => "odinadcatyj" ] #original: array:6 [ "id" => 5460 "created_at" => "2026-04-10 13:58:26" "updated_at" => null "name" => "11" "field_cases" => array:6 [ …6] "field_translit" => "odinadcatyj" ] #changes: [] #casts: [] #classCastCache: [] #attributeCastCache: [] #dateFormat: null #appends: [] #dispatchesEvents: [] #observables: [] #relations: [] #touches: [] +timestamps: true +usesUniqueIds: false #hidden: [] #visible: [] #fillable: [] #guarded: array:1 [ 0 => "*" ] } ] #escapeWhenCastingToString: false } "field_publisher" => Illuminate\Database\Eloquent\Collection {#1133 #items: array:1 [ 0 => App\Models\Term {#1134 #connection: "mysql" #table: "terms" #primaryKey: "id" #keyType: "int" +incrementing: false #with: [] #withCount: [] +preventsLazyLoading: false #perPage: 15 +exists: true +wasRecentlyCreated: false #escapeWhenCastingToString: false #attributes: array:6 [ "id" => 5158 "created_at" => "2026-04-10 13:58:26" "updated_at" => null "name" => "Илекса" "field_cases" => null "field_translit" => "ileksa" ] #original: array:6 [ "id" => 5158 "created_at" => "2026-04-10 13:58:26" "updated_at" => null "name" => "Илекса" "field_cases" => null "field_translit" => "ileksa" ] #changes: [] #casts: [] #classCastCache: [] #attributeCastCache: [] #dateFormat: null #appends: [] #dispatchesEvents: [] #observables: [] #relations: [] #touches: [] +timestamps: true +usesUniqueIds: false #hidden: [] #visible: [] #fillable: [] #guarded: array:1 [ 0 => "*" ] } ] #escapeWhenCastingToString: false } "field_author" => Illuminate\Database\Eloquent\Collection {#1135 #items: array:3 [ 0 => App\Models\Term {#1136 #connection: "mysql" #table: "terms" #primaryKey: "id" #keyType: "int" +incrementing: false #with: [] #withCount: [] +preventsLazyLoading: false #perPage: 15 +exists: true +wasRecentlyCreated: false #escapeWhenCastingToString: false #attributes: array:12 [ "id" => 4102 "created_at" => "2026-04-10 13:58:26" "updated_at" => null "name" => "Гельфгат" "field_bio" => null "field_degree_rp" => null "field_foreign_lang_name" => null "field_foreign_lang_patronymic" => null "field_foreign_lang_surname" => null "field_name" => "Илья" "field_patronymic" => "Маркович" "field_surname_rp" => null ] #original: array:12 [ "id" => 4102 "created_at" => "2026-04-10 13:58:26" "updated_at" => null "name" => "Гельфгат" "field_bio" => null "field_degree_rp" => null "field_foreign_lang_name" => null "field_foreign_lang_patronymic" => null "field_foreign_lang_surname" => null "field_name" => "Илья" "field_patronymic" => "Маркович" "field_surname_rp" => null ] #changes: [] #casts: [] #classCastCache: [] #attributeCastCache: [] #dateFormat: null #appends: [] #dispatchesEvents: [] #observables: [] #relations: [] #touches: [] +timestamps: true +usesUniqueIds: false #hidden: [] #visible: [] #fillable: [] #guarded: array:1 [ 0 => "*" ] } 1 => App\Models\Term {#1137 #connection: "mysql" #table: "terms" #primaryKey: "id" #keyType: "int" +incrementing: false #with: [] #withCount: [] +preventsLazyLoading: false #perPage: 15 +exists: true +wasRecentlyCreated: false #escapeWhenCastingToString: false #attributes: array:12 [ "id" => 4104 "created_at" => "2026-04-10 13:58:26" "updated_at" => null "name" => "Генденштейн" "field_bio" => null "field_degree_rp" => null "field_foreign_lang_name" => null "field_foreign_lang_patronymic" => null "field_foreign_lang_surname" => null "field_name" => "Лев" "field_patronymic" => "Элевич" "field_surname_rp" => "Генденштейна" ] #original: array:12 [ "id" => 4104 "created_at" => "2026-04-10 13:58:26" "updated_at" => null "name" => "Генденштейн" "field_bio" => null "field_degree_rp" => null "field_foreign_lang_name" => null "field_foreign_lang_patronymic" => null "field_foreign_lang_surname" => null "field_name" => "Лев" "field_patronymic" => "Элевич" "field_surname_rp" => "Генденштейна" ] #changes: [] #casts: [] #classCastCache: [] #attributeCastCache: [] #dateFormat: null #appends: [] #dispatchesEvents: [] #observables: [] #relations: [] #touches: [] +timestamps: true +usesUniqueIds: false #hidden: [] #visible: [] #fillable: [] #guarded: array:1 [ 0 => "*" ] } 2 => App\Models\Term {#1138 #connection: "mysql" #table: "terms" #primaryKey: "id" #keyType: "int" +incrementing: false #with: [] #withCount: [] +preventsLazyLoading: false #perPage: 15 +exists: true +wasRecentlyCreated: false #escapeWhenCastingToString: false #attributes: array:12 [ "id" => 4583 "created_at" => "2026-04-10 13:58:26" "updated_at" => null "name" => "Кирик" "field_bio" => null "field_degree_rp" => null "field_foreign_lang_name" => null "field_foreign_lang_patronymic" => null "field_foreign_lang_surname" => null "field_name" => "Леонид" "field_patronymic" => "Анатольевич" "field_surname_rp" => null ] #original: array:12 [ "id" => 4583 "created_at" => "2026-04-10 13:58:26" "updated_at" => null "name" => "Кирик" "field_bio" => null "field_degree_rp" => null "field_foreign_lang_name" => null "field_foreign_lang_patronymic" => null "field_foreign_lang_surname" => null "field_name" => "Леонид" "field_patronymic" => "Анатольевич" "field_surname_rp" => null ] #changes: [] #casts: [] #classCastCache: [] #attributeCastCache: [] #dateFormat: null #appends: [] #dispatchesEvents: [] #observables: [] #relations: [] #touches: [] +timestamps: true +usesUniqueIds: false #hidden: [] #visible: [] #fillable: [] #guarded: array:1 [ 0 => "*" ] } ] #escapeWhenCastingToString: false } "field_author_foreign" => Illuminate\Database\Eloquent\Collection {#1139 #items: [] #escapeWhenCastingToString: false } "field_book_type" => Illuminate\Database\Eloquent\Collection {#1140 #items: array:1 [ 0 => App\Models\Term {#1141 #connection: "mysql" #table: "terms" #primaryKey: "id" #keyType: "int" +incrementing: false #with: [] #withCount: [] +preventsLazyLoading: false #perPage: 15 +exists: true +wasRecentlyCreated: false #escapeWhenCastingToString: false #attributes: array:10 [ "id" => 6673 "created_at" => "2026-04-10 13:58:26" "updated_at" => null "name" => "Учебник, задачник" "field_book_type_foreign" => null "field_cases" => array:6 [ …6] "field_plural_form" => null "field_short_name" => null "field_short_name_foreign" => null "field_translit" => "uchebnik, zadachnik" ] #original: array:10 [ "id" => 6673 "created_at" => "2026-04-10 13:58:26" "updated_at" => null "name" => "Учебник, задачник" "field_book_type_foreign" => null "field_cases" => array:6 [ …6] "field_plural_form" => null "field_short_name" => null "field_short_name_foreign" => null "field_translit" => "uchebnik, zadachnik" ] #changes: [] #casts: [] #classCastCache: [] #attributeCastCache: [] #dateFormat: null #appends: [] #dispatchesEvents: [] #observables: [] #relations: [] #touches: [] +timestamps: true +usesUniqueIds: false #hidden: [] #visible: [] #fillable: [] #guarded: array:1 [ 0 => "*" ] } ] #escapeWhenCastingToString: false } "field_country" => Illuminate\Database\Eloquent\Collection {#1142 #items: array:1 [ 0 => App\Models\Term {#1143 #connection: "mysql" #table: "terms" #primaryKey: "id" #keyType: "int" +incrementing: false #with: [] #withCount: [] +preventsLazyLoading: false #perPage: 15 +exists: true +wasRecentlyCreated: false #escapeWhenCastingToString: false #attributes: array:6 [ "id" => 9 "created_at" => "2026-04-10 13:58:26" "updated_at" => null "name" => "Россия" "field_cases" => array:6 [ …6] "field_translit" => "rossiya" ] #original: array:6 [ "id" => 9 "created_at" => "2026-04-10 13:58:26" "updated_at" => null "name" => "Россия" "field_cases" => array:6 [ …6] "field_translit" => "rossiya" ] #changes: [] #casts: [] #classCastCache: [] #attributeCastCache: [] #dateFormat: null #appends: [] #dispatchesEvents: [] #observables: [] #relations: [] #touches: [] +timestamps: true +usesUniqueIds: false #hidden: [] #visible: [] #fillable: [] #guarded: array:1 [ 0 => "*" ] } ] #escapeWhenCastingToString: false } "field_city" => Illuminate\Database\Eloquent\Collection {#1144 #items: array:1 [ 0 => App\Models\Term {#1145 #connection: "mysql" #table: "terms" #primaryKey: "id" #keyType: "int" +incrementing: false #with: [] #withCount: [] +preventsLazyLoading: false #perPage: 15 +exists: true +wasRecentlyCreated: false #escapeWhenCastingToString: false #attributes: array:6 [ "id" => 15 "created_at" => "2026-04-10 13:58:26" "updated_at" => null "name" => "Москва" "field_cases" => array:6 [ …6] "field_translit" => "moskva" ] #original: array:6 [ "id" => 15 "created_at" => "2026-04-10 13:58:26" "updated_at" => null "name" => "Москва" "field_cases" => array:6 [ …6] "field_translit" => "moskva" ] #changes: [] #casts: [] #classCastCache: [] #attributeCastCache: [] #dateFormat: null #appends: [] #dispatchesEvents: [] #observables: [] #relations: [] #touches: [] +timestamps: true +usesUniqueIds: false #hidden: [] #visible: [] #fillable: [] #guarded: array:1 [ 0 => "*" ] } ] #escapeWhenCastingToString: false } "field_series" => Illuminate\Database\Eloquent\Collection {#1146 #items: [] #escapeWhenCastingToString: false } "field_umk" => Illuminate\Database\Eloquent\Collection {#1147 #items: [] #escapeWhenCastingToString: false } "field_level_of_education" => Illuminate\Database\Eloquent\Collection {#1148 #items: [] #escapeWhenCastingToString: false } "field_standart_of_education" => Illuminate\Database\Eloquent\Collection {#1149 #items: [] #escapeWhenCastingToString: false } "field_publication_number" => "6" "field_publication_type" => Illuminate\Database\Eloquent\Collection {#1150 #items: array:1 [ 0 => App\Models\Term {#1151 #connection: "mysql" #table: "terms" #primaryKey: "id" #keyType: "int" +incrementing: false #with: [] #withCount: [] +preventsLazyLoading: false #perPage: 15 +exists: true +wasRecentlyCreated: false #escapeWhenCastingToString: false #attributes: array:6 [ "id" => 35 "created_at" => "2026-04-10 13:58:26" "updated_at" => null "name" => "исправленное" "field_cases" => array:6 [ …6] "field_translit" => "ispravlennoe" ] #original: array:6 [ "id" => 35 "created_at" => "2026-04-10 13:58:26" "updated_at" => null "name" => "исправленное" "field_cases" => array:6 [ …6] "field_translit" => "ispravlennoe" ] #changes: [] #casts: [] #classCastCache: [] #attributeCastCache: [] #dateFormat: null #appends: [] #dispatchesEvents: [] #observables: [] #relations: [] #touches: [] +timestamps: true +usesUniqueIds: false #hidden: [] #visible: [] #fillable: [] #guarded: array:1 [ 0 => "*" ] } ] #escapeWhenCastingToString: false } "field_under_the_edition" => Illuminate\Database\Eloquent\Collection {#1152 #items: [] #escapeWhenCastingToString: false } "field_under_the_edition_degree" => null "field_cover_description" => "мужчина в красном, летит на черном шаре" "field_publication_year" => "2005" "field_publication_year_until" => null "field_part" => "" "field_part_writing" => "" "field_second_foreign_language" => null "field_for_whom" => "Учебное издание" "field_allowed" => null "field_reserve_field" => null "field_link_to_source" => null "field_tasks_count" => "1001" "field_priority" => null "field_default_folder" => "/fizika_08/gelfgat-u/" "field_isbn" => "978-5-89237-332-6" "field_cover" => array:1 [ 0 => "/media/fizika_08/gelfgat-u/covers/cover1.webp?ts=1755898771" ] "field_cover_alts" => array:1 [ 0 => "" ] "field_covers" => array:1 [ 0 => array:4 [ "path" => "/media/fizika_08/gelfgat-u/covers/cover1.webp?ts=1755898771" "alt" => "" "width" => "1813" "height" => "2441" ] ] "field_popular_book" => "0" "field_recommended_books" => Illuminate\Database\Eloquent\Collection {#1153 #items: [] #escapeWhenCastingToString: false } "field_new_book" => Illuminate\Database\Eloquent\Collection {#1154 #items: [] #escapeWhenCastingToString: false } "field_old_book" => Illuminate\Database\Eloquent\Collection {#1155 #items: [] #escapeWhenCastingToString: false } "field_url" => "/8-klass/fizika/ileksa-gelfgat-uchebnik" "field_cover_color" => Illuminate\Database\Eloquent\Collection {#1156 #items: array:1 [ 0 => App\Models\Term {#1157 #connection: "mysql" #table: "terms" #primaryKey: "id" #keyType: "int" +incrementing: false #with: [] #withCount: [] +preventsLazyLoading: false #perPage: 15 +exists: true +wasRecentlyCreated: false #escapeWhenCastingToString: false #attributes: array:6 [ "id" => 49 "created_at" => "2026-04-10 13:58:26" "updated_at" => null "name" => "синий" "field_cases" => array:6 [ …6] "field_translit" => "siniy" ] #original: array:6 [ "id" => 49 "created_at" => "2026-04-10 13:58:26" "updated_at" => null "name" => "синий" "field_cases" => array:6 [ …6] "field_translit" => "siniy" ] #changes: [] #casts: [] #classCastCache: [] #attributeCastCache: [] #dateFormat: null #appends: [] #dispatchesEvents: [] #observables: [] #relations: [] #touches: [] +timestamps: true +usesUniqueIds: false #hidden: [] #visible: [] #fillable: [] #guarded: array:1 [ 0 => "*" ] } ] #escapeWhenCastingToString: false } "field_metatags_title" => null "field_metatags_description" => null "field_h1" => null "field_description_top" => null "field_description_bottom" => null "breadcrumbs" => array:3 [ "class" => 379 "subject" => 556 "class_subject" => 492 ] ] #original: array:50 [ "id" => 5401 "created_at" => "2026-04-10 13:58:26" "updated_at" => null "field_tree_default_status" => "tasks" "field_pages_status" => null "field_subject" => Illuminate\Database\Eloquent\Collection {#1127} "field_class" => Illuminate\Database\Eloquent\Collection {#1128} "field_publisher" => Illuminate\Database\Eloquent\Collection {#1133} "field_author" => Illuminate\Database\Eloquent\Collection {#1135} "field_author_foreign" => Illuminate\Database\Eloquent\Collection {#1139} "field_book_type" => Illuminate\Database\Eloquent\Collection {#1140} "field_country" => Illuminate\Database\Eloquent\Collection {#1142} "field_city" => Illuminate\Database\Eloquent\Collection {#1144} "field_series" => Illuminate\Database\Eloquent\Collection {#1146} "field_umk" => Illuminate\Database\Eloquent\Collection {#1147} "field_level_of_education" => Illuminate\Database\Eloquent\Collection {#1148} "field_standart_of_education" => Illuminate\Database\Eloquent\Collection {#1149} "field_publication_number" => "6" "field_publication_type" => Illuminate\Database\Eloquent\Collection {#1150} "field_under_the_edition" => Illuminate\Database\Eloquent\Collection {#1152} "field_under_the_edition_degree" => null "field_cover_description" => "мужчина в красном, летит на черном шаре" "field_publication_year" => "2005" "field_publication_year_until" => null "field_part" => "" "field_part_writing" => "" "field_second_foreign_language" => null "field_for_whom" => "Учебное издание" "field_allowed" => null "field_reserve_field" => null "field_link_to_source" => null "field_tasks_count" => "1001" "field_priority" => null "field_default_folder" => "/fizika_08/gelfgat-u/" "field_isbn" => "978-5-89237-332-6" "field_cover" => array:1 [ 0 => "/media/fizika_08/gelfgat-u/covers/cover1.webp?ts=1755898771" ] "field_cover_alts" => array:1 [ 0 => "" ] "field_covers" => array:1 [ 0 => array:4 [ "path" => "/media/fizika_08/gelfgat-u/covers/cover1.webp?ts=1755898771" "alt" => "" "width" => "1813" "height" => "2441" ] ] "field_popular_book" => "0" "field_recommended_books" => Illuminate\Database\Eloquent\Collection {#1153} "field_new_book" => Illuminate\Database\Eloquent\Collection {#1154} "field_old_book" => Illuminate\Database\Eloquent\Collection {#1155} "field_url" => "/8-klass/fizika/ileksa-gelfgat-uchebnik" "field_cover_color" => Illuminate\Database\Eloquent\Collection {#1156} "field_metatags_title" => null "field_metatags_description" => null "field_h1" => null "field_description_top" => null "field_description_bottom" => null "breadcrumbs" => array:3 [ "class" => 379 "subject" => 556 "class_subject" => 492 ] ] #changes: [] #casts: [] #classCastCache: [] #attributeCastCache: [] #dateFormat: null #appends: [] #dispatchesEvents: [] #observables: [] #relations: [] #touches: [] +timestamps: true +usesUniqueIds: false #hidden: [] #visible: [] #fillable: [] #guarded: array:1 [ 0 => "*" ] } ] #escapeWhenCastingToString: false } "branch_parent" => Illuminate\Database\Eloquent\Collection {#1158 #items: [] #escapeWhenCastingToString: false } ] #original: array:24 [ "id" => 1287866 "created_at" => "2026-04-10 13:58:26" "updated_at" => null "field_display_title" => "Задачи" "field_branch_order" => null "field_url" => null "field_branch_type" => Illuminate\Database\Eloquent\Collection {#1124} "field_page_start" => "5" "field_branch_display" => "0" "field_branch_expanded" => "0" "field_display_branch_in_title" => "1" "field_display_task_interval" => "0" "field_display_branch_page" => "1" "field_branch_title_in_content" => "0" "field_navigation_title" => null "field_metatags_title" => null "field_metatags_description" => null "field_h1" => null "field_description_top" => null "field_description_bottom" => null "field_branch_cover" => [] "field_branch_covers" => [] "book" => Illuminate\Database\Eloquent\Collection {#1160} "branch_parent" => Illuminate\Database\Eloquent\Collection {#1158} ] #changes: [] #casts: [] #classCastCache: [] #attributeCastCache: [] #dateFormat: null #appends: [] #dispatchesEvents: [] #observables: [] #relations: [] #touches: [] +timestamps: true +usesUniqueIds: false #hidden: [] #visible: [] #fillable: [] #guarded: array:1 [ 0 => "*" ] } 1 => App\Models\Branch {#1159 #connection: "mysql" #table: "branches" #primaryKey: "id" #keyType: "int" +incrementing: true #with: [] #withCount: [] +preventsLazyLoading: false #perPage: 15 +exists: true +wasRecentlyCreated: false #escapeWhenCastingToString: false #attributes: array:24 [ "id" => 1287891 "created_at" => "2026-04-10 13:58:26" "updated_at" => null "field_display_title" => "Теория относительности и атомная физика" "field_branch_order" => null "field_url" => null "field_branch_type" => Illuminate\Database\Eloquent\Collection {#1161 #items: [] #escapeWhenCastingToString: false } "field_page_start" => "128" "field_branch_display" => "0" "field_branch_expanded" => "0" "field_display_branch_in_title" => "1" "field_display_task_interval" => "0" "field_display_branch_page" => "1" "field_branch_title_in_content" => "0" "field_navigation_title" => null "field_metatags_title" => null "field_metatags_description" => null "field_h1" => null "field_description_top" => null "field_description_bottom" => null "field_branch_cover" => [] "field_branch_covers" => [] "book" => Illuminate\Database\Eloquent\Collection {#1162 #items: array:1 [ 0 => App\Models\Book {#1125} ] #escapeWhenCastingToString: false } "branch_parent" => Illuminate\Database\Eloquent\Collection {#1163 #items: array:1 [ 0 => App\Models\Branch {#1034} ] #escapeWhenCastingToString: false } ] #original: array:24 [ "id" => 1287891 "created_at" => "2026-04-10 13:58:26" "updated_at" => null "field_display_title" => "Теория относительности и атомная физика" "field_branch_order" => null "field_url" => null "field_branch_type" => Illuminate\Database\Eloquent\Collection {#1161} "field_page_start" => "128" "field_branch_display" => "0" "field_branch_expanded" => "0" "field_display_branch_in_title" => "1" "field_display_task_interval" => "0" "field_display_branch_page" => "1" "field_branch_title_in_content" => "0" "field_navigation_title" => null "field_metatags_title" => null "field_metatags_description" => null "field_h1" => null "field_description_top" => null "field_description_bottom" => null "field_branch_cover" => [] "field_branch_covers" => [] "book" => Illuminate\Database\Eloquent\Collection {#1162} "branch_parent" => Illuminate\Database\Eloquent\Collection {#1163} ] #changes: [] #casts: [] #classCastCache: [] #attributeCastCache: [] #dateFormat: null #appends: [] #dispatchesEvents: [] #observables: [] #relations: [] #touches: [] +timestamps: true +usesUniqueIds: false #hidden: [] #visible: [] #fillable: [] #guarded: array:1 [ 0 => "*" ] } 2 => App\Models\Branch {#1164 #connection: "mysql" #table: "branches" #primaryKey: "id" #keyType: "int" +incrementing: true #with: [] #withCount: [] +preventsLazyLoading: false #perPage: 15 +exists: true +wasRecentlyCreated: false #escapeWhenCastingToString: false #attributes: array:24 [ "id" => 1287892 "created_at" => "2026-04-10 13:58:26" "updated_at" => null "field_display_title" => "21. Пространство, время, движение в теории относительности" "field_branch_order" => null "field_url" => null "field_branch_type" => Illuminate\Database\Eloquent\Collection {#1165 #items: [] #escapeWhenCastingToString: false } "field_page_start" => "128" "field_branch_display" => "0" "field_branch_expanded" => "0" "field_display_branch_in_title" => "1" "field_display_task_interval" => "0" "field_display_branch_page" => "1" "field_branch_title_in_content" => "0" "field_navigation_title" => null "field_metatags_title" => null "field_metatags_description" => null "field_h1" => null "field_description_top" => null "field_description_bottom" => null "field_branch_cover" => [] "field_branch_covers" => [] "book" => Illuminate\Database\Eloquent\Collection {#1166 #items: array:1 [ 0 => App\Models\Book {#1125} ] #escapeWhenCastingToString: false } "branch_parent" => Illuminate\Database\Eloquent\Collection {#1175 #items: array:1 [ 0 => App\Models\Branch {#1174 #connection: "mysql" #table: "branches" #primaryKey: "id" #keyType: "int" +incrementing: true #with: [] #withCount: [] +preventsLazyLoading: false #perPage: 15 +exists: true +wasRecentlyCreated: false #escapeWhenCastingToString: false #attributes: array:24 [ "id" => 1287891 "created_at" => "2026-04-10 13:58:26" "updated_at" => null "field_display_title" => "Теория относительности и атомная физика" "field_branch_order" => null "field_url" => null "field_branch_type" => Illuminate\Database\Eloquent\Collection {#1176 …2} "field_page_start" => "128" "field_branch_display" => "0" "field_branch_expanded" => "0" "field_display_branch_in_title" => "1" "field_display_task_interval" => "0" "field_display_branch_page" => "1" "field_branch_title_in_content" => "0" "field_navigation_title" => null "field_metatags_title" => null "field_metatags_description" => null "field_h1" => null "field_description_top" => null "field_description_bottom" => null "field_branch_cover" => [] "field_branch_covers" => [] "book" => Illuminate\Database\Eloquent\Collection {#1177 …2} "branch_parent" => Illuminate\Database\Eloquent\Collection {#1178 …2} ] #original: array:24 [ "id" => 1287891 "created_at" => "2026-04-10 13:58:26" "updated_at" => null "field_display_title" => "Теория относительности и атомная физика" "field_branch_order" => null "field_url" => null "field_branch_type" => Illuminate\Database\Eloquent\Collection {#1176 …2} "field_page_start" => "128" "field_branch_display" => "0" "field_branch_expanded" => "0" "field_display_branch_in_title" => "1" "field_display_task_interval" => "0" "field_display_branch_page" => "1" "field_branch_title_in_content" => "0" "field_navigation_title" => null "field_metatags_title" => null "field_metatags_description" => null "field_h1" => null "field_description_top" => null "field_description_bottom" => null "field_branch_cover" => [] "field_branch_covers" => [] "book" => Illuminate\Database\Eloquent\Collection {#1177 …2} "branch_parent" => Illuminate\Database\Eloquent\Collection {#1178 …2} ] #changes: [] #casts: [] #classCastCache: [] #attributeCastCache: [] #dateFormat: null #appends: [] #dispatchesEvents: [] #observables: [] #relations: [] #touches: [] +timestamps: true +usesUniqueIds: false #hidden: [] #visible: [] #fillable: [] #guarded: array:1 [ 0 => "*" ] } ] #escapeWhenCastingToString: false } ] #original: array:24 [ "id" => 1287892 "created_at" => "2026-04-10 13:58:26" "updated_at" => null "field_display_title" => "21. Пространство, время, движение в теории относительности" "field_branch_order" => null "field_url" => null "field_branch_type" => Illuminate\Database\Eloquent\Collection {#1165} "field_page_start" => "128" "field_branch_display" => "0" "field_branch_expanded" => "0" "field_display_branch_in_title" => "1" "field_display_task_interval" => "0" "field_display_branch_page" => "1" "field_branch_title_in_content" => "0" "field_navigation_title" => null "field_metatags_title" => null "field_metatags_description" => null "field_h1" => null "field_description_top" => null "field_description_bottom" => null "field_branch_cover" => [] "field_branch_covers" => [] "book" => Illuminate\Database\Eloquent\Collection {#1166} "branch_parent" => Illuminate\Database\Eloquent\Collection {#1175} ] #changes: [] #casts: [] #classCastCache: [] #attributeCastCache: [] #dateFormat: null #appends: [] #dispatchesEvents: [] #observables: [] #relations: [] #touches: [] +timestamps: true +usesUniqueIds: false #hidden: [] #visible: [] #fillable: [] #guarded: array:1 [ 0 => "*" ] } ] #escapeWhenCastingToString: false } "content" => Illuminate\Database\Eloquent\Collection {#1111 #items: array:3 [ 0 => App\Models\Element {#1103 #connection: "mysql" #table: "elements" #primaryKey: "id" #keyType: "int" +incrementing: true #with: [] #withCount: [] +preventsLazyLoading: false #perPage: 15 +exists: true +wasRecentlyCreated: false #escapeWhenCastingToString: false #attributes: array:7 [ "id" => 1479224 "created_at" => "2026-04-10 13:58:26" "updated_at" => null "edition" => Illuminate\Database\Eloquent\Collection {#1096 #items: array:1 [ 0 => App\Models\Edition {#1104 #connection: "mysql" #table: "editions" #primaryKey: "id" #keyType: "int" +incrementing: false #with: [] #withCount: [] +preventsLazyLoading: false #perPage: 15 +exists: true +wasRecentlyCreated: false #escapeWhenCastingToString: false #attributes: array:21 [ "id" => 5410 "created_at" => "2026-04-10 13:58:26" "updated_at" => null "title" => "Условие" "field_order" => "1" "field_publisher" => Illuminate\Database\Eloquent\Collection {#1101 …2} "field_content_type" => "free" "field_content_mode" => "text, image" "field_page_content_mode" => "image" "field_content_text_checked" => null "field_page_content_text_checked" => "0" "field_solution_author" => "Автор" "field_moderator" => "stas" "field_edition_type" => "statement" "field_root_dir" => "0-" "field_responsible" => Illuminate\Database\Eloquent\Collection {#1100 …2} "field_comment" => null "field_similar_book" => Illuminate\Database\Eloquent\Collection {#1099 …2} "field_process_formula" => "katex" "field_edition_group" => Illuminate\Database\Eloquent\Collection {#1097 …2} "field_content_source" => null ] #original: array:21 [ "id" => 5410 "created_at" => "2026-04-10 13:58:26" "updated_at" => null "title" => "Условие" "field_order" => "1" "field_publisher" => Illuminate\Database\Eloquent\Collection {#1101 …2} "field_content_type" => "free" "field_content_mode" => "text, image" "field_page_content_mode" => "image" "field_content_text_checked" => null "field_page_content_text_checked" => "0" "field_solution_author" => "Автор" "field_moderator" => "stas" "field_edition_type" => "statement" "field_root_dir" => "0-" "field_responsible" => Illuminate\Database\Eloquent\Collection {#1100 …2} "field_comment" => null "field_similar_book" => Illuminate\Database\Eloquent\Collection {#1099 …2} "field_process_formula" => "katex" "field_edition_group" => Illuminate\Database\Eloquent\Collection {#1097 …2} "field_content_source" => null ] #changes: [] #casts: [] #classCastCache: [] #attributeCastCache: [] #dateFormat: null #appends: [] #dispatchesEvents: [] #observables: [] #relations: [] #touches: [] +timestamps: true +usesUniqueIds: false #hidden: [] #visible: [] #fillable: [] #guarded: array:1 [ 0 => "*" ] } ] #escapeWhenCastingToString: false } "task" => array:2 [ "refs" => "1288789" "type" => "task" ] "text" => "<p><strong>21.4*.</strong> Релятивистская частица распадается на два одинаковых «осколка». Скорость одного из них равна нулю. Найдите скорость $\text{v}$ частицы до распада и скорость $v_2$ второго «осколка», если известно, что при распаде такой же <em>неподвижной</em> частицы оба «осколка» имеют скорость $\text{u}$.</p>" "img" => array:1 [ 0 => array:5 [ "name" => "4-1.jpg" "alt" => null "width" => "1444" "height" => 329 "path" => "/media/fizika_08/gelfgat-u/0-21/4-1.webp?ts=1756050150" ] ] ] #original: array:7 [ "id" => 1479224 "created_at" => "2026-04-10 13:58:26" "updated_at" => null "edition" => Illuminate\Database\Eloquent\Collection {#1096} "task" => array:2 [ "refs" => "1288789" "type" => "task" ] "text" => "<p><strong>21.4*.</strong> Релятивистская частица распадается на два одинаковых «осколка». Скорость одного из них равна нулю. Найдите скорость $\text{v}$ частицы до распада и скорость $v_2$ второго «осколка», если известно, что при распаде такой же <em>неподвижной</em> частицы оба «осколка» имеют скорость $\text{u}$.</p>" "img" => array:1 [ 0 => array:5 [ "name" => "4-1.jpg" "alt" => null "width" => "1444" "height" => 329 "path" => "/media/fizika_08/gelfgat-u/0-21/4-1.webp?ts=1756050150" ] ] ] #changes: [] #casts: [] #classCastCache: [] #attributeCastCache: [] #dateFormat: null #appends: [] #dispatchesEvents: [] #observables: [] #relations: [] #touches: [] +timestamps: true +usesUniqueIds: false #hidden: [] #visible: [] #fillable: [] #guarded: array:1 [ 0 => "*" ] } 1 => App\Models\Element {#1098 #connection: "mysql" #table: "elements" #primaryKey: "id" #keyType: "int" +incrementing: true #with: [] #withCount: [] +preventsLazyLoading: false #perPage: 15 +exists: true +wasRecentlyCreated: false #escapeWhenCastingToString: false #attributes: array:6 [ "id" => 1479565 "created_at" => "2026-04-10 13:58:26" "updated_at" => null "edition" => Illuminate\Database\Eloquent\Collection {#1086 #items: array:1 [ 0 => App\Models\Edition {#1095 #connection: "mysql" #table: "editions" #primaryKey: "id" #keyType: "int" +incrementing: false #with: [] #withCount: [] +preventsLazyLoading: false #perPage: 15 +exists: true +wasRecentlyCreated: false #escapeWhenCastingToString: false #attributes: array:21 [ "id" => 5411 "created_at" => "2026-04-10 13:58:26" "updated_at" => null "title" => "Решение" "field_order" => "2" "field_publisher" => Illuminate\Database\Eloquent\Collection {#1094 …2} "field_content_type" => "free" "field_content_mode" => "image" "field_page_content_mode" => "" "field_content_text_checked" => "0" "field_page_content_text_checked" => "0" "field_solution_author" => "Автор" "field_moderator" => "stas" "field_edition_type" => "solution" "field_root_dir" => "1-" "field_responsible" => Illuminate\Database\Eloquent\Collection {#1092 …2} "field_comment" => null "field_similar_book" => Illuminate\Database\Eloquent\Collection {#1088 …2} "field_process_formula" => "" "field_edition_group" => Illuminate\Database\Eloquent\Collection {#1091 …2} "field_content_source" => null ] #original: array:21 [ "id" => 5411 "created_at" => "2026-04-10 13:58:26" "updated_at" => null "title" => "Решение" "field_order" => "2" "field_publisher" => Illuminate\Database\Eloquent\Collection {#1094 …2} "field_content_type" => "free" "field_content_mode" => "image" "field_page_content_mode" => "" "field_content_text_checked" => "0" "field_page_content_text_checked" => "0" "field_solution_author" => "Автор" "field_moderator" => "stas" "field_edition_type" => "solution" "field_root_dir" => "1-" "field_responsible" => Illuminate\Database\Eloquent\Collection {#1092 …2} "field_comment" => null "field_similar_book" => Illuminate\Database\Eloquent\Collection {#1088 …2} "field_process_formula" => "" "field_edition_group" => Illuminate\Database\Eloquent\Collection {#1091 …2} "field_content_source" => null ] #changes: [] #casts: [] #classCastCache: [] #attributeCastCache: [] #dateFormat: null #appends: [] #dispatchesEvents: [] #observables: [] #relations: [] #touches: [] +timestamps: true +usesUniqueIds: false #hidden: [] #visible: [] #fillable: [] #guarded: array:1 [ 0 => "*" ] } ] #escapeWhenCastingToString: false } "task" => array:2 [ "refs" => "1288789" "type" => "task" ] "img" => array:1 [ 0 => array:5 [ "name" => "4-1.jpg" "alt" => null "width" => "1408" "height" => 535 "path" => "/media/fizika_08/gelfgat-u/1-21/4-1.webp?ts=1756050220" ] ] ] #original: array:6 [ "id" => 1479565 "created_at" => "2026-04-10 13:58:26" "updated_at" => null "edition" => Illuminate\Database\Eloquent\Collection {#1086} "task" => array:2 [ "refs" => "1288789" "type" => "task" ] "img" => array:1 [ 0 => array:5 [ "name" => "4-1.jpg" "alt" => null "width" => "1408" "height" => 535 "path" => "/media/fizika_08/gelfgat-u/1-21/4-1.webp?ts=1756050220" ] ] ] #changes: [] #casts: [] #classCastCache: [] #attributeCastCache: [] #dateFormat: null #appends: [] #dispatchesEvents: [] #observables: [] #relations: [] #touches: [] +timestamps: true +usesUniqueIds: false #hidden: [] #visible: [] #fillable: [] #guarded: array:1 [ 0 => "*" ] } 2 => App\Models\Element {#1090 #connection: "mysql" #table: "elements" #primaryKey: "id" #keyType: "int" +incrementing: true #with: [] #withCount: [] +preventsLazyLoading: false #perPage: 15 +exists: true +wasRecentlyCreated: false #escapeWhenCastingToString: false #attributes: array:6 [ "id" => 1738482 "created_at" => "2026-04-10 13:58:26" "updated_at" => null "edition" => Illuminate\Database\Eloquent\Collection {#1080 #items: array:1 [ 0 => App\Models\Edition {#1089 #connection: "mysql" #table: "editions" #primaryKey: "id" #keyType: "int" +incrementing: false #with: [] #withCount: [] +preventsLazyLoading: false #perPage: 15 +exists: true +wasRecentlyCreated: false #escapeWhenCastingToString: false #attributes: array:21 [ "id" => 6336 "created_at" => "2026-04-10 13:58:26" "updated_at" => null "title" => "Решение 2" "field_order" => "3" "field_publisher" => Illuminate\Database\Eloquent\Collection {#1081 …2} "field_content_type" => "free" "field_content_mode" => "text" "field_page_content_mode" => "" "field_content_text_checked" => null "field_page_content_text_checked" => "0" "field_solution_author" => "Gemini 2.5 Pro" "field_moderator" => "tolik" "field_edition_type" => "solution" "field_root_dir" => "2-" "field_responsible" => Illuminate\Database\Eloquent\Collection {#1085 …2} "field_comment" => null "field_similar_book" => Illuminate\Database\Eloquent\Collection {#1084 …2} "field_process_formula" => "katex" "field_edition_group" => Illuminate\Database\Eloquent\Collection {#1083 …2} "field_content_source" => null ] #original: array:21 [ "id" => 6336 "created_at" => "2026-04-10 13:58:26" "updated_at" => null "title" => "Решение 2" "field_order" => "3" "field_publisher" => Illuminate\Database\Eloquent\Collection {#1081 …2} "field_content_type" => "free" "field_content_mode" => "text" "field_page_content_mode" => "" "field_content_text_checked" => null "field_page_content_text_checked" => "0" "field_solution_author" => "Gemini 2.5 Pro" "field_moderator" => "tolik" "field_edition_type" => "solution" "field_root_dir" => "2-" "field_responsible" => Illuminate\Database\Eloquent\Collection {#1085 …2} "field_comment" => null "field_similar_book" => Illuminate\Database\Eloquent\Collection {#1084 …2} "field_process_formula" => "katex" "field_edition_group" => Illuminate\Database\Eloquent\Collection {#1083 …2} "field_content_source" => null ] #changes: [] #casts: [] #classCastCache: [] #attributeCastCache: [] #dateFormat: null #appends: [] #dispatchesEvents: [] #observables: [] #relations: [] #touches: [] +timestamps: true +usesUniqueIds: false #hidden: [] #visible: [] #fillable: [] #guarded: array:1 [ 0 => "*" ] } ] #escapeWhenCastingToString: false } "task" => array:2 [ "refs" => "1288789" "type" => "task" ] "text" => "<p><strong>Дано:</strong></p><p>Релятивистская частица распадается на два одинаковых осколка.</p><p>Скорость первого осколка: $v_1 = 0$.</p><p>При распаде такой же неподвижной частицы, скорость каждого из осколков равна $\text{u}$.</p><p><strong>Найти:</strong></p><p>Скорость частицы до распада: $\text{v}$</p><p>Скорость второго осколка: $v_2$</p><p><strong>Решение:</strong></p><p>Рассмотрим два случая распада, описанные в условии задачи, с точки зрения законов сохранения энергии и импульса в специальной теории относительности.</p><p>Пусть $M_0$ — масса покоя исходной частицы, а $m_0$ — масса покоя каждого из двух одинаковых осколков.</p><p><strong>1.</strong> Распад неподвижной частицы.</p><p>В этом случае начальная частица покоится ($v=0$). Ее энергия — это энергия покоя $E_{нач} = M_0 c^2$, а ее импульс равен нулю, $p_{нач} = 0$.</p><p>После распада образуются два осколка, которые разлетаются в противоположные стороны со скоростями $\text{u}$ и $-u$ (согласно закону сохранения импульса). Суммарная энергия осколков равна:</p><p>$E_{кон} = \gamma(u) m_0 c^2 + \gamma(-u) m_0 c^2 = 2 \gamma(u) m_0 c^2$, где $\gamma(u) = \frac{1}{\sqrt{1-u^2/c^2}}$ — релятивистский фактор.</p><p>Согласно закону сохранения энергии:</p><p>$E_{нач} = E_{кон}$</p><p>$M_0 c^2 = 2 \gamma(u) m_0 c^2$</p><p>Отсюда находим соотношение между массами покоя исходной частицы и осколков:</p><p>$M_0 = 2 \gamma(u) m_0 = \frac{2 m_0}{\sqrt{1-u^2/c^2}}$ (1)</p><p><strong>2.</strong> Распад движущейся частицы.</p><p>Теперь рассмотрим случай, когда исходная частица движется со скоростью $\text{v}$. Ее начальная энергия и импульс равны:</p><p>$E_{нач} = \gamma(v) M_0 c^2$</p><p>$p_{нач} = \gamma(v) M_0 v$</p><p>После распада один осколок покоится ($v_1 = 0$), а второй движется со скоростью $v_2$. Их суммарная энергия и импульс равны:</p><p>$E_{кон} = \gamma(0) m_0 c^2 + \gamma(v_2) m_0 c^2 = m_0 c^2 + \gamma(v_2) m_0 c^2$</p><p>$p_{кон} = \gamma(0) m_0 \cdot 0 + \gamma(v_2) m_0 v_2 = \gamma(v_2) m_0 v_2$</p><p>Применим законы сохранения энергии и импульса для этого случая:</p><p>Закон сохранения энергии:</p><p>$\gamma(v) M_0 c^2 = m_0 c^2 + \gamma(v_2) m_0 c^2$</p><p>$\gamma(v) M_0 = m_0 (1 + \gamma(v_2))$ (2)</p><p>Закон сохранения импульса:</p><p>$\gamma(v) M_0 v = \gamma(v_2) m_0 v_2$ (3)</p><p>Теперь подставим соотношение масс (1) в уравнения (2) и (3), чтобы исключить массы:</p><p>Из (2): $\gamma(v) (2 \gamma(u) m_0) = m_0 (1 + \gamma(v_2)) \implies 2 \gamma(v) \gamma(u) = 1 + \gamma(v_2)$ (4)</p><p>Из (3): $\gamma(v) (2 \gamma(u) m_0) v = \gamma(v_2) m_0 v_2 \implies 2 \gamma(v) \gamma(u) v = \gamma(v_2) v_2$ (5)</p><p>Мы получили систему из двух уравнений (4) и (5) с двумя неизвестными $\text{v}$ и $v_2$. Решим ее.</p><p>Из уравнения (4) выразим $\gamma(v_2)$: $\gamma(v_2) = 2 \gamma(v) \gamma(u) - 1$.</p><p>Подставим это выражение в уравнение (5):</p><p>$2 \gamma(v) \gamma(u) v = (2 \gamma(v) \gamma(u) - 1) v_2$</p><p>Отсюда $v_2 = \frac{2 \gamma(v) \gamma(u) v}{2 \gamma(v) \gamma(u) - 1}$.</p><p>Теперь воспользуемся основным релятивистским тождеством для второго осколка: $E_2^2 - (p_2 c)^2 = (m_0 c^2)^2$. В терминах $\gamma$-фактора это $\gamma(v_2)^2 m_0^2 c^4 - (\gamma(v_2) m_0 v_2)^2 c^2 = m_0^2 c^4$, что упрощается до $\gamma(v_2)^2 (c^2 - v_2^2) = c^2$, или $\gamma(v_2)^2 (1 - v_2^2/c^2) = 1$.</p><p>Умножим уравнение (5) на $c^2$ и разделим на $v_2$, а затем возведем в квадрат. И умножим уравнение (4) на $m_0 c^2$ и возведем в квадрат.</p><p>Более простой способ — это разделить уравнение (5) на уравнение (4):</p><p>$\frac{2 \gamma(v) \gamma(u) v}{2 \gamma(v) \gamma(u)} = \frac{\gamma(v_2) v_2}{1 + \gamma(v_2)}$</p><p>$v = \frac{\gamma(v_2) v_2}{1 + \gamma(v_2)}$</p><p>Из (4) имеем $1+\gamma(v_2) = 2\gamma(v)\gamma(u)$. Из (5) имеем $\gamma(v_2)v_2 = 2\gamma(v)\gamma(u)v$. Подстановка в полученное выражение для $\text{v}$ дает тождество $v=v$, что не помогает.</p><p>Вернемся к системе. Давайте перейдем в систему покоя исходной частицы. В этой системе (штрихованной) осколки разлетаются со скоростями $u' = u$ и $u'' = -u$. Лабораторная система движется относительно этой системы со скоростью $-v$. Тогда, по закону сложения скоростей, скорость осколков в лабораторной системе будет:</p><p>$v_1 = \frac{u'' + v}{1 + u''v/c^2} = \frac{-u + v}{1 - uv/c^2}$</p><p>$v_2 = \frac{u' + v}{1 + u'v/c^2} = \frac{u + v}{1 + uv/c^2}$</p><p>По условию, скорость одного из осколков в лабораторной системе равна нулю: $v_1 = 0$.</p><p>$\frac{-u + v}{1 - uv/c^2} = 0$</p><p>Отсюда следует, что числитель должен быть равен нулю: $-u+v=0$, то есть $v=u$.</p><p>Это и есть скорость исходной частицы.</p><p>Теперь найдем скорость второго осколка $v_2$, подставив $v=u$ в соответствующую формулу:</p><p>$v_2 = \frac{u + u}{1 + u \cdot u / c^2} = \frac{2u}{1 + u^2/c^2}$</p><p><strong>Ответ:</strong> Скорость частицы до распада $v = u$. Скорость второго осколка $v_2 = \frac{2u}{1 + u^2/c^2}$.</p>" ] #original: array:6 [ "id" => 1738482 "created_at" => "2026-04-10 13:58:26" "updated_at" => null "edition" => Illuminate\Database\Eloquent\Collection {#1080} "task" => array:2 [ "refs" => "1288789" "type" => "task" ] "text" => "<p><strong>Дано:</strong></p><p>Релятивистская частица распадается на два одинаковых осколка.</p><p>Скорость первого осколка: $v_1 = 0$.</p><p>При распаде такой же неподвижной частицы, скорость каждого из осколков равна $\text{u}$.</p><p><strong>Найти:</strong></p><p>Скорость частицы до распада: $\text{v}$</p><p>Скорость второго осколка: $v_2$</p><p><strong>Решение:</strong></p><p>Рассмотрим два случая распада, описанные в условии задачи, с точки зрения законов сохранения энергии и импульса в специальной теории относительности.</p><p>Пусть $M_0$ — масса покоя исходной частицы, а $m_0$ — масса покоя каждого из двух одинаковых осколков.</p><p><strong>1.</strong> Распад неподвижной частицы.</p><p>В этом случае начальная частица покоится ($v=0$). Ее энергия — это энергия покоя $E_{нач} = M_0 c^2$, а ее импульс равен нулю, $p_{нач} = 0$.</p><p>После распада образуются два осколка, которые разлетаются в противоположные стороны со скоростями $\text{u}$ и $-u$ (согласно закону сохранения импульса). Суммарная энергия осколков равна:</p><p>$E_{кон} = \gamma(u) m_0 c^2 + \gamma(-u) m_0 c^2 = 2 \gamma(u) m_0 c^2$, где $\gamma(u) = \frac{1}{\sqrt{1-u^2/c^2}}$ — релятивистский фактор.</p><p>Согласно закону сохранения энергии:</p><p>$E_{нач} = E_{кон}$</p><p>$M_0 c^2 = 2 \gamma(u) m_0 c^2$</p><p>Отсюда находим соотношение между массами покоя исходной частицы и осколков:</p><p>$M_0 = 2 \gamma(u) m_0 = \frac{2 m_0}{\sqrt{1-u^2/c^2}}$ (1)</p><p><strong>2.</strong> Распад движущейся частицы.</p><p>Теперь рассмотрим случай, когда исходная частица движется со скоростью $\text{v}$. Ее начальная энергия и импульс равны:</p><p>$E_{нач} = \gamma(v) M_0 c^2$</p><p>$p_{нач} = \gamma(v) M_0 v$</p><p>После распада один осколок покоится ($v_1 = 0$), а второй движется со скоростью $v_2$. Их суммарная энергия и импульс равны:</p><p>$E_{кон} = \gamma(0) m_0 c^2 + \gamma(v_2) m_0 c^2 = m_0 c^2 + \gamma(v_2) m_0 c^2$</p><p>$p_{кон} = \gamma(0) m_0 \cdot 0 + \gamma(v_2) m_0 v_2 = \gamma(v_2) m_0 v_2$</p><p>Применим законы сохранения энергии и импульса для этого случая:</p><p>Закон сохранения энергии:</p><p>$\gamma(v) M_0 c^2 = m_0 c^2 + \gamma(v_2) m_0 c^2$</p><p>$\gamma(v) M_0 = m_0 (1 + \gamma(v_2))$ (2)</p><p>Закон сохранения импульса:</p><p>$\gamma(v) M_0 v = \gamma(v_2) m_0 v_2$ (3)</p><p>Теперь подставим соотношение масс (1) в уравнения (2) и (3), чтобы исключить массы:</p><p>Из (2): $\gamma(v) (2 \gamma(u) m_0) = m_0 (1 + \gamma(v_2)) \implies 2 \gamma(v) \gamma(u) = 1 + \gamma(v_2)$ (4)</p><p>Из (3): $\gamma(v) (2 \gamma(u) m_0) v = \gamma(v_2) m_0 v_2 \implies 2 \gamma(v) \gamma(u) v = \gamma(v_2) v_2$ (5)</p><p>Мы получили систему из двух уравнений (4) и (5) с двумя неизвестными $\text{v}$ и $v_2$. Решим ее.</p><p>Из уравнения (4) выразим $\gamma(v_2)$: $\gamma(v_2) = 2 \gamma(v) \gamma(u) - 1$.</p><p>Подставим это выражение в уравнение (5):</p><p>$2 \gamma(v) \gamma(u) v = (2 \gamma(v) \gamma(u) - 1) v_2$</p><p>Отсюда $v_2 = \frac{2 \gamma(v) \gamma(u) v}{2 \gamma(v) \gamma(u) - 1}$.</p><p>Теперь воспользуемся основным релятивистским тождеством для второго осколка: $E_2^2 - (p_2 c)^2 = (m_0 c^2)^2$. В терминах $\gamma$-фактора это $\gamma(v_2)^2 m_0^2 c^4 - (\gamma(v_2) m_0 v_2)^2 c^2 = m_0^2 c^4$, что упрощается до $\gamma(v_2)^2 (c^2 - v_2^2) = c^2$, или $\gamma(v_2)^2 (1 - v_2^2/c^2) = 1$.</p><p>Умножим уравнение (5) на $c^2$ и разделим на $v_2$, а затем возведем в квадрат. И умножим уравнение (4) на $m_0 c^2$ и возведем в квадрат.</p><p>Более простой способ — это разделить уравнение (5) на уравнение (4):</p><p>$\frac{2 \gamma(v) \gamma(u) v}{2 \gamma(v) \gamma(u)} = \frac{\gamma(v_2) v_2}{1 + \gamma(v_2)}$</p><p>$v = \frac{\gamma(v_2) v_2}{1 + \gamma(v_2)}$</p><p>Из (4) имеем $1+\gamma(v_2) = 2\gamma(v)\gamma(u)$. Из (5) имеем $\gamma(v_2)v_2 = 2\gamma(v)\gamma(u)v$. Подстановка в полученное выражение для $\text{v}$ дает тождество $v=v$, что не помогает.</p><p>Вернемся к системе. Давайте перейдем в систему покоя исходной частицы. В этой системе (штрихованной) осколки разлетаются со скоростями $u' = u$ и $u'' = -u$. Лабораторная система движется относительно этой системы со скоростью $-v$. Тогда, по закону сложения скоростей, скорость осколков в лабораторной системе будет:</p><p>$v_1 = \frac{u'' + v}{1 + u''v/c^2} = \frac{-u + v}{1 - uv/c^2}$</p><p>$v_2 = \frac{u' + v}{1 + u'v/c^2} = \frac{u + v}{1 + uv/c^2}$</p><p>По условию, скорость одного из осколков в лабораторной системе равна нулю: $v_1 = 0$.</p><p>$\frac{-u + v}{1 - uv/c^2} = 0$</p><p>Отсюда следует, что числитель должен быть равен нулю: $-u+v=0$, то есть $v=u$.</p><p>Это и есть скорость исходной частицы.</p><p>Теперь найдем скорость второго осколка $v_2$, подставив $v=u$ в соответствующую формулу:</p><p>$v_2 = \frac{u + u}{1 + u \cdot u / c^2} = \frac{2u}{1 + u^2/c^2}$</p><p><strong>Ответ:</strong> Скорость частицы до распада $v = u$. Скорость второго осколка $v_2 = \frac{2u}{1 + u^2/c^2}$.</p>" ] #changes: [] #casts: [] #classCastCache: [] #attributeCastCache: [] #dateFormat: null #appends: [] #dispatchesEvents: [] #observables: [] #relations: [] #touches: [] +timestamps: true +usesUniqueIds: false #hidden: [] #visible: [] #fillable: [] #guarded: array:1 [ 0 => "*" ] } ] #escapeWhenCastingToString: false } "next" => array:2 [ "refs" => "1288790" "type" => "task" ] "previous" => array:2 [ "refs" => "1288788" "type" => "task" ] "book" => Illuminate\Database\Eloquent\Collection {#1107 #items: array:1 [ 0 => App\Models\Book {#1125} ] #escapeWhenCastingToString: false } "page" => Illuminate\Database\Eloquent\Collection {#1110 #items: array:1 [ 0 => App\Models\BookPage {#1075 #connection: "mysql" #table: "book_pages" #primaryKey: "id" #keyType: "int" +incrementing: true #with: [] #withCount: [] +preventsLazyLoading: false #perPage: 15 +exists: true +wasRecentlyCreated: false #escapeWhenCastingToString: false #attributes: array:21 [ "id" => 1340479 "created_at" => "2026-04-10 13:58:26" "updated_at" => null "field_page_start" => "128" "field_url" => "/8-klass/fizika/ileksa-gelfgat-uchebnik/page-128" "field_display_title" => "128" "field_folder" => "1" "field_image_name" => "128" "field_branch_parent" => Illuminate\Database\Eloquent\Collection {#1078 #items: [] #escapeWhenCastingToString: false } "field_weight" => "0" "field_book_parent" => Illuminate\Database\Eloquent\Collection {#1082 #items: array:1 [ 0 => App\Models\Book {#1125} ] #escapeWhenCastingToString: false } "field_metatags_title" => null "field_metatags_description" => null "field_h1" => null "field_description_top" => null "field_description_bottom" => null "edition_groups" => Illuminate\Database\Eloquent\Collection {#1079 #items: [] #escapeWhenCastingToString: false } "content" => Illuminate\Database\Eloquent\Collection {#1168 #items: array:1 [ 0 => App\Models\Element {#1116 #connection: "mysql" #table: "elements" #primaryKey: "id" #keyType: "int" +incrementing: true #with: [] #withCount: [] +preventsLazyLoading: false #perPage: 15 +exists: true +wasRecentlyCreated: false #escapeWhenCastingToString: false #attributes: array:6 [ "id" => 1518600 "created_at" => "2026-04-10 13:58:26" "updated_at" => null "edition" => Illuminate\Database\Eloquent\Collection {#1167 …2} "book_page" => array:2 [ …2] "img" => array:1 [ …1] ] #original: array:6 [ "id" => 1518600 "created_at" => "2026-04-10 13:58:26" "updated_at" => null "edition" => Illuminate\Database\Eloquent\Collection {#1167 …2} "book_page" => array:2 [ …2] "img" => array:1 [ …1] ] #changes: [] #casts: [] #classCastCache: [] #attributeCastCache: [] #dateFormat: null #appends: [] #dispatchesEvents: [] #observables: [] #relations: [] #touches: [] +timestamps: true +usesUniqueIds: false #hidden: [] #visible: [] #fillable: [] #guarded: array:1 [ 0 => "*" ] } ] #escapeWhenCastingToString: false } "next" => array:2 [ "refs" => "1340480" "type" => "book_page" ] "previous" => array:2 [ "refs" => "1340478" "type" => "book_page" ] "tasks" => Illuminate\Database\Eloquent\Collection {#1288 #items: array:6 [ 0 => App\Models\Task {#1300 #connection: "mysql" #table: "tasks" #primaryKey: "id" #keyType: "int" +incrementing: true #with: [] #withCount: [] +preventsLazyLoading: false #perPage: 15 +exists: true +wasRecentlyCreated: false #escapeWhenCastingToString: false #attributes: array:24 [ "id" => 1288786 "created_at" => "2026-04-10 13:58:26" "updated_at" => null "field_page_start" => "128" "field_page_end" => null "field_url" => "/8-klass/fizika/ileksa-gelfgat-uchebnik/21-1" "field_display_title" => "21.1" "field_outside_task" => null "field_task_type" => Illuminate\Database\Eloquent\Collection {#1301 …2} "field_metatags_title" => null "field_metatags_description" => null "field_h1" => null "field_description_top" => null "field_description_bottom" => null "field_match" => null "breadcrumbs" => [] "edition_groups" => Illuminate\Database\Eloquent\Collection {#1302 …2} "top_parent_branch" => Illuminate\Database\Eloquent\Collection {#1303 …2} "parent_branches" => Illuminate\Database\Eloquent\Collection {#1304 …2} "content" => Illuminate\Database\Eloquent\Collection {#1307 …2} "next" => array:2 [ …2] "previous" => array:2 [ …2] "book" => Illuminate\Database\Eloquent\Collection {#1313 …2} "page" => array:2 [ …2] ] #original: array:24 [ "id" => 1288786 "created_at" => "2026-04-10 13:58:26" "updated_at" => null "field_page_start" => "128" "field_page_end" => null "field_url" => "/8-klass/fizika/ileksa-gelfgat-uchebnik/21-1" "field_display_title" => "21.1" "field_outside_task" => null "field_task_type" => Illuminate\Database\Eloquent\Collection {#1301 …2} "field_metatags_title" => null "field_metatags_description" => null "field_h1" => null "field_description_top" => null "field_description_bottom" => null "field_match" => null "breadcrumbs" => [] "edition_groups" => Illuminate\Database\Eloquent\Collection {#1302 …2} "top_parent_branch" => Illuminate\Database\Eloquent\Collection {#1303 …2} "parent_branches" => Illuminate\Database\Eloquent\Collection {#1304 …2} "content" => Illuminate\Database\Eloquent\Collection {#1307 …2} "next" => array:2 [ …2] "previous" => array:2 [ …2] "book" => Illuminate\Database\Eloquent\Collection {#1313 …2} "page" => array:2 [ …2] ] #changes: [] #casts: [] #classCastCache: [] #attributeCastCache: [] #dateFormat: null #appends: [] #dispatchesEvents: [] #observables: [] #relations: [] #touches: [] +timestamps: true +usesUniqueIds: false #hidden: [] #visible: [] #fillable: [] #guarded: array:1 [ 0 => "*" ] } 1 => App\Models\Task {#1306 #connection: "mysql" #table: "tasks" #primaryKey: "id" #keyType: "int" +incrementing: true #with: [] #withCount: [] +preventsLazyLoading: false #perPage: 15 +exists: true +wasRecentlyCreated: false #escapeWhenCastingToString: false #attributes: array:24 [ "id" => 1288787 "created_at" => "2026-04-10 13:58:26" "updated_at" => null "field_page_start" => "128" "field_page_end" => null "field_url" => "/8-klass/fizika/ileksa-gelfgat-uchebnik/21-2" "field_display_title" => "21.2" "field_outside_task" => null "field_task_type" => Illuminate\Database\Eloquent\Collection {#1305 …2} "field_metatags_title" => null "field_metatags_description" => null "field_h1" => null "field_description_top" => null "field_description_bottom" => null "field_match" => null "breadcrumbs" => [] "edition_groups" => Illuminate\Database\Eloquent\Collection {#1312 …2} "top_parent_branch" => Illuminate\Database\Eloquent\Collection {#1314 …2} "parent_branches" => Illuminate\Database\Eloquent\Collection {#1310 …2} "content" => Illuminate\Database\Eloquent\Collection {#1309 …2} "next" => array:2 [ …2] "previous" => array:2 [ …2] "book" => Illuminate\Database\Eloquent\Collection {#1327 …2} "page" => array:2 [ …2] ] #original: array:24 [ "id" => 1288787 "created_at" => "2026-04-10 13:58:26" "updated_at" => null "field_page_start" => "128" "field_page_end" => null "field_url" => "/8-klass/fizika/ileksa-gelfgat-uchebnik/21-2" "field_display_title" => "21.2" "field_outside_task" => null "field_task_type" => Illuminate\Database\Eloquent\Collection {#1305 …2} "field_metatags_title" => null "field_metatags_description" => null "field_h1" => null "field_description_top" => null "field_description_bottom" => null "field_match" => null "breadcrumbs" => [] "edition_groups" => Illuminate\Database\Eloquent\Collection {#1312 …2} "top_parent_branch" => Illuminate\Database\Eloquent\Collection {#1314 …2} "parent_branches" => Illuminate\Database\Eloquent\Collection {#1310 …2} "content" => Illuminate\Database\Eloquent\Collection {#1309 …2} "next" => array:2 [ …2] "previous" => array:2 [ …2] "book" => Illuminate\Database\Eloquent\Collection {#1327 …2} "page" => array:2 [ …2] ] #changes: [] #casts: [] #classCastCache: [] #attributeCastCache: [] #dateFormat: null #appends: [] #dispatchesEvents: [] #observables: [] #relations: [] #touches: [] +timestamps: true +usesUniqueIds: false #hidden: [] #visible: [] #fillable: [] #guarded: array:1 [ 0 => "*" ] } 2 => App\Models\Task {#1311 #connection: "mysql" #table: "tasks" #primaryKey: "id" #keyType: "int" +incrementing: true #with: [] #withCount: [] +preventsLazyLoading: false #perPage: 15 +exists: true +wasRecentlyCreated: false #escapeWhenCastingToString: false #attributes: array:24 [ "id" => 1288788 "created_at" => "2026-04-10 13:58:26" "updated_at" => null "field_page_start" => "128" "field_page_end" => null "field_url" => "/8-klass/fizika/ileksa-gelfgat-uchebnik/21-3" "field_display_title" => "21.3" "field_outside_task" => null "field_task_type" => Illuminate\Database\Eloquent\Collection {#1308 …2} "field_metatags_title" => null "field_metatags_description" => null "field_h1" => null "field_description_top" => null "field_description_bottom" => null "field_match" => null "breadcrumbs" => [] "edition_groups" => Illuminate\Database\Eloquent\Collection {#1326 …2} "top_parent_branch" => Illuminate\Database\Eloquent\Collection {#1328 …2} "parent_branches" => Illuminate\Database\Eloquent\Collection {#1324 …2} "content" => Illuminate\Database\Eloquent\Collection {#1323 …2} "next" => array:2 [ …2] "previous" => array:2 [ …2] "book" => Illuminate\Database\Eloquent\Collection {#1341 …2} "page" => array:2 [ …2] ] #original: array:24 [ "id" => 1288788 "created_at" => "2026-04-10 13:58:26" "updated_at" => null "field_page_start" => "128" "field_page_end" => null "field_url" => "/8-klass/fizika/ileksa-gelfgat-uchebnik/21-3" "field_display_title" => "21.3" "field_outside_task" => null "field_task_type" => Illuminate\Database\Eloquent\Collection {#1308 …2} "field_metatags_title" => null "field_metatags_description" => null "field_h1" => null "field_description_top" => null "field_description_bottom" => null "field_match" => null "breadcrumbs" => [] "edition_groups" => Illuminate\Database\Eloquent\Collection {#1326 …2} "top_parent_branch" => Illuminate\Database\Eloquent\Collection {#1328 …2} "parent_branches" => Illuminate\Database\Eloquent\Collection {#1324 …2} "content" => Illuminate\Database\Eloquent\Collection {#1323 …2} "next" => array:2 [ …2] "previous" => array:2 [ …2] "book" => Illuminate\Database\Eloquent\Collection {#1341 …2} "page" => array:2 [ …2] ] #changes: [] #casts: [] #classCastCache: [] #attributeCastCache: [] #dateFormat: null #appends: [] #dispatchesEvents: [] #observables: [] #relations: [] #touches: [] +timestamps: true +usesUniqueIds: false #hidden: [] #visible: [] #fillable: [] #guarded: array:1 [ 0 => "*" ] } 3 => App\Models\Task {#1325 #connection: "mysql" #table: "tasks" #primaryKey: "id" #keyType: "int" +incrementing: true #with: [] #withCount: [] +preventsLazyLoading: false #perPage: 15 +exists: true +wasRecentlyCreated: false #escapeWhenCastingToString: false #attributes: array:24 [ "id" => 1288789 "created_at" => "2026-04-10 13:58:26" "updated_at" => null "field_page_start" => "128" "field_page_end" => null "field_url" => "/8-klass/fizika/ileksa-gelfgat-uchebnik/21-4" "field_display_title" => "21.4" "field_outside_task" => null "field_task_type" => Illuminate\Database\Eloquent\Collection {#1322 …2} "field_metatags_title" => null "field_metatags_description" => null "field_h1" => null "field_description_top" => null "field_description_bottom" => null "field_match" => null "breadcrumbs" => [] "edition_groups" => Illuminate\Database\Eloquent\Collection {#1340 …2} "top_parent_branch" => Illuminate\Database\Eloquent\Collection {#1342 …2} "parent_branches" => Illuminate\Database\Eloquent\Collection {#1338 …2} "content" => Illuminate\Database\Eloquent\Collection {#1336 …2} "next" => array:2 [ …2] "previous" => array:2 [ …2] "book" => Illuminate\Database\Eloquent\Collection {#1339 …2} "page" => array:2 [ …2] ] #original: array:24 [ "id" => 1288789 "created_at" => "2026-04-10 13:58:26" "updated_at" => null "field_page_start" => "128" "field_page_end" => null "field_url" => "/8-klass/fizika/ileksa-gelfgat-uchebnik/21-4" "field_display_title" => "21.4" "field_outside_task" => null "field_task_type" => Illuminate\Database\Eloquent\Collection {#1322 …2} "field_metatags_title" => null "field_metatags_description" => null "field_h1" => null "field_description_top" => null "field_description_bottom" => null "field_match" => null "breadcrumbs" => [] "edition_groups" => Illuminate\Database\Eloquent\Collection {#1340 …2} "top_parent_branch" => Illuminate\Database\Eloquent\Collection {#1342 …2} "parent_branches" => Illuminate\Database\Eloquent\Collection {#1338 …2} "content" => Illuminate\Database\Eloquent\Collection {#1336 …2} "next" => array:2 [ …2] "previous" => array:2 [ …2] "book" => Illuminate\Database\Eloquent\Collection {#1339 …2} "page" => array:2 [ …2] ] #changes: [] #casts: [] #classCastCache: [] #attributeCastCache: [] #dateFormat: null #appends: [] #dispatchesEvents: [] #observables: [] #relations: [] #touches: [] +timestamps: true +usesUniqueIds: false #hidden: [] #visible: [] #fillable: [] #guarded: array:1 [ 0 => "*" ] } 4 => App\Models\Task {#1337 #connection: "mysql" #table: "tasks" #primaryKey: "id" #keyType: "int" +incrementing: true #with: [] #withCount: [] +preventsLazyLoading: false #perPage: 15 +exists: true +wasRecentlyCreated: false #escapeWhenCastingToString: false #attributes: array:24 [ "id" => 1288790 "created_at" => "2026-04-10 13:58:26" "updated_at" => null "field_page_start" => "128" "field_page_end" => null "field_url" => "/8-klass/fizika/ileksa-gelfgat-uchebnik/21-5" "field_display_title" => "21.5" "field_outside_task" => null "field_task_type" => Illuminate\Database\Eloquent\Collection {#1350 …2} "field_metatags_title" => null "field_metatags_description" => null "field_h1" => null "field_description_top" => null "field_description_bottom" => null "field_match" => null "breadcrumbs" => [] "edition_groups" => Illuminate\Database\Eloquent\Collection {#1351 …2} "top_parent_branch" => Illuminate\Database\Eloquent\Collection {#1352 …2} "parent_branches" => Illuminate\Database\Eloquent\Collection {#1353 …2} "content" => Illuminate\Database\Eloquent\Collection {#1356 …2} "next" => array:2 [ …2] "previous" => array:2 [ …2] "book" => Illuminate\Database\Eloquent\Collection {#1362 …2} "page" => array:2 [ …2] ] #original: array:24 [ "id" => 1288790 "created_at" => "2026-04-10 13:58:26" "updated_at" => null "field_page_start" => "128" "field_page_end" => null "field_url" => "/8-klass/fizika/ileksa-gelfgat-uchebnik/21-5" "field_display_title" => "21.5" "field_outside_task" => null "field_task_type" => Illuminate\Database\Eloquent\Collection {#1350 …2} "field_metatags_title" => null "field_metatags_description" => null "field_h1" => null "field_description_top" => null "field_description_bottom" => null …10 ] #changes: [] #casts: [] #classCastCache: [] #attributeCastCache: [] #dateFormat: null #appends: [] #dispatchesEvents: [] #observables: [] #relations: [] #touches: [] +timestamps: true +usesUniqueIds: false #hidden: [] #visible: [] #fillable: [] #guarded: array:1 [ …1] } 5 => App\Models\Task {#1355 #connection: "mysql" #table: "tasks" #primaryKey: "id" #keyType: "int" +incrementing: true #with: [] #withCount: [] +preventsLazyLoading: false #perPage: 15 +exists: true +wasRecentlyCreated: false #escapeWhenCastingToString: false #attributes: array:24 [ …24] #original: array:24 [ …24] #changes: [] #casts: [] #classCastCache: [] #attributeCastCache: [] #dateFormat: null #appends: [] #dispatchesEvents: [] #observables: [] #relations: [] #touches: [] +timestamps: true +usesUniqueIds: false #hidden: [] #visible: [] #fillable: [] #guarded: array:1 [ …1] } ] #escapeWhenCastingToString: false } ] #original: array:21 [ "id" => 1340479 "created_at" => "2026-04-10 13:58:26" "updated_at" => null "field_page_start" => "128" "field_url" => "/8-klass/fizika/ileksa-gelfgat-uchebnik/page-128" "field_display_title" => "128" "field_folder" => "1" "field_image_name" => "128" "field_branch_parent" => Illuminate\Database\Eloquent\Collection {#1078} "field_weight" => "0" "field_book_parent" => Illuminate\Database\Eloquent\Collection {#1082} "field_metatags_title" => null "field_metatags_description" => null "field_h1" => null "field_description_top" => null "field_description_bottom" => null "edition_groups" => Illuminate\Database\Eloquent\Collection {#1079} "content" => Illuminate\Database\Eloquent\Collection {#1168} "next" => array:2 [ "refs" => "1340480" "type" => "book_page" ] "previous" => array:2 [ "refs" => "1340478" "type" => "book_page" ] "tasks" => Illuminate\Database\Eloquent\Collection {#1288} ] #changes: [] #casts: [] #classCastCache: [] #attributeCastCache: [] #dateFormat: null #appends: [] #dispatchesEvents: [] #observables: [] #relations: [] #touches: [] +timestamps: true +usesUniqueIds: false #hidden: [] #visible: [] #fillable: [] #guarded: array:1 [ 0 => "*" ] } ] #escapeWhenCastingToString: false } ] #original: array:24 [ "id" => 1288789 "created_at" => "2026-04-10 13:58:26" "updated_at" => null "field_page_start" => "128" "field_page_end" => null "field_url" => "/8-klass/fizika/ileksa-gelfgat-uchebnik/21-4" "field_display_title" => "21.4" "field_outside_task" => null "field_task_type" => Illuminate\Database\Eloquent\Collection {#1037} "field_metatags_title" => null "field_metatags_description" => null "field_h1" => null "field_description_top" => null "field_description_bottom" => null "field_match" => null "breadcrumbs" => [] "edition_groups" => Illuminate\Database\Eloquent\Collection {#1035} "top_parent_branch" => Illuminate\Database\Eloquent\Collection {#1076} "parent_branches" => Illuminate\Database\Eloquent\Collection {#1113} "content" => Illuminate\Database\Eloquent\Collection {#1111} "next" => array:2 [ "refs" => "1288790" "type" => "task" ] "previous" => array:2 [ "refs" => "1288788" "type" => "task" ] "book" => Illuminate\Database\Eloquent\Collection {#1107} "page" => array:2 [ "refs" => "1340479" "type" => "book_page" ] ] #changes: [] #casts: [] #classCastCache: [] #attributeCastCache: [] #dateFormat: null #appends: [] #dispatchesEvents: [] #observables: [] #relations: [] #touches: [] +timestamps: true +usesUniqueIds: false #hidden: [] #visible: [] #fillable: [] #guarded: array:1 [ 0 => "*" ] }
№21.4 (с. 128)
Условие. №21.4 (с. 128)
скриншот условия
21.4*. Релятивистская частица распадается на два одинаковых «осколка». Скорость одного из них равна нулю. Найдите скорость $\text{v}$ частицы до распада и скорость $v_2$ второго «осколка», если известно, что при распаде такой же неподвижной частицы оба «осколка» имеют скорость $\text{u}$.
Решение. №21.4 (с. 128)
Решение 2. №21.4 (с. 128)
Дано:
Релятивистская частица распадается на два одинаковых осколка.
Скорость первого осколка: $v_1 = 0$.
При распаде такой же неподвижной частицы, скорость каждого из осколков равна $\text{u}$.
Найти:
Скорость частицы до распада: $\text{v}$
Скорость второго осколка: $v_2$
Решение:
Рассмотрим два случая распада, описанные в условии задачи, с точки зрения законов сохранения энергии и импульса в специальной теории относительности.
Пусть $M_0$ — масса покоя исходной частицы, а $m_0$ — масса покоя каждого из двух одинаковых осколков.
1. Распад неподвижной частицы.
В этом случае начальная частица покоится ($v=0$). Ее энергия — это энергия покоя $E_{нач} = M_0 c^2$, а ее импульс равен нулю, $p_{нач} = 0$.
После распада образуются два осколка, которые разлетаются в противоположные стороны со скоростями $\text{u}$ и $-u$ (согласно закону сохранения импульса). Суммарная энергия осколков равна:
$E_{кон} = \gamma(u) m_0 c^2 + \gamma(-u) m_0 c^2 = 2 \gamma(u) m_0 c^2$, где $\gamma(u) = \frac{1}{\sqrt{1-u^2/c^2}}$ — релятивистский фактор.
Согласно закону сохранения энергии:
$E_{нач} = E_{кон}$
$M_0 c^2 = 2 \gamma(u) m_0 c^2$
Отсюда находим соотношение между массами покоя исходной частицы и осколков:
$M_0 = 2 \gamma(u) m_0 = \frac{2 m_0}{\sqrt{1-u^2/c^2}}$ (1)
2. Распад движущейся частицы.
Теперь рассмотрим случай, когда исходная частица движется со скоростью $\text{v}$. Ее начальная энергия и импульс равны:
$E_{нач} = \gamma(v) M_0 c^2$
$p_{нач} = \gamma(v) M_0 v$
После распада один осколок покоится ($v_1 = 0$), а второй движется со скоростью $v_2$. Их суммарная энергия и импульс равны:
$E_{кон} = \gamma(0) m_0 c^2 + \gamma(v_2) m_0 c^2 = m_0 c^2 + \gamma(v_2) m_0 c^2$
$p_{кон} = \gamma(0) m_0 \cdot 0 + \gamma(v_2) m_0 v_2 = \gamma(v_2) m_0 v_2$
Применим законы сохранения энергии и импульса для этого случая:
Закон сохранения энергии:
$\gamma(v) M_0 c^2 = m_0 c^2 + \gamma(v_2) m_0 c^2$
$\gamma(v) M_0 = m_0 (1 + \gamma(v_2))$ (2)
Закон сохранения импульса:
$\gamma(v) M_0 v = \gamma(v_2) m_0 v_2$ (3)
Теперь подставим соотношение масс (1) в уравнения (2) и (3), чтобы исключить массы:
Из (2): $\gamma(v) (2 \gamma(u) m_0) = m_0 (1 + \gamma(v_2)) \implies 2 \gamma(v) \gamma(u) = 1 + \gamma(v_2)$ (4)
Из (3): $\gamma(v) (2 \gamma(u) m_0) v = \gamma(v_2) m_0 v_2 \implies 2 \gamma(v) \gamma(u) v = \gamma(v_2) v_2$ (5)
Мы получили систему из двух уравнений (4) и (5) с двумя неизвестными $\text{v}$ и $v_2$. Решим ее.
Из уравнения (4) выразим $\gamma(v_2)$: $\gamma(v_2) = 2 \gamma(v) \gamma(u) - 1$.
Подставим это выражение в уравнение (5):
$2 \gamma(v) \gamma(u) v = (2 \gamma(v) \gamma(u) - 1) v_2$
Отсюда $v_2 = \frac{2 \gamma(v) \gamma(u) v}{2 \gamma(v) \gamma(u) - 1}$.
Теперь воспользуемся основным релятивистским тождеством для второго осколка: $E_2^2 - (p_2 c)^2 = (m_0 c^2)^2$. В терминах $\gamma$-фактора это $\gamma(v_2)^2 m_0^2 c^4 - (\gamma(v_2) m_0 v_2)^2 c^2 = m_0^2 c^4$, что упрощается до $\gamma(v_2)^2 (c^2 - v_2^2) = c^2$, или $\gamma(v_2)^2 (1 - v_2^2/c^2) = 1$.
Умножим уравнение (5) на $c^2$ и разделим на $v_2$, а затем возведем в квадрат. И умножим уравнение (4) на $m_0 c^2$ и возведем в квадрат.
Более простой способ — это разделить уравнение (5) на уравнение (4):
$\frac{2 \gamma(v) \gamma(u) v}{2 \gamma(v) \gamma(u)} = \frac{\gamma(v_2) v_2}{1 + \gamma(v_2)}$
$v = \frac{\gamma(v_2) v_2}{1 + \gamma(v_2)}$
Из (4) имеем $1+\gamma(v_2) = 2\gamma(v)\gamma(u)$. Из (5) имеем $\gamma(v_2)v_2 = 2\gamma(v)\gamma(u)v$. Подстановка в полученное выражение для $\text{v}$ дает тождество $v=v$, что не помогает.
Вернемся к системе. Давайте перейдем в систему покоя исходной частицы. В этой системе (штрихованной) осколки разлетаются со скоростями $u' = u$ и $u'' = -u$. Лабораторная система движется относительно этой системы со скоростью $-v$. Тогда, по закону сложения скоростей, скорость осколков в лабораторной системе будет:
$v_1 = \frac{u'' + v}{1 + u''v/c^2} = \frac{-u + v}{1 - uv/c^2}$
$v_2 = \frac{u' + v}{1 + u'v/c^2} = \frac{u + v}{1 + uv/c^2}$
По условию, скорость одного из осколков в лабораторной системе равна нулю: $v_1 = 0$.
$\frac{-u + v}{1 - uv/c^2} = 0$
Отсюда следует, что числитель должен быть равен нулю: $-u+v=0$, то есть $v=u$.
Это и есть скорость исходной частицы.
Теперь найдем скорость второго осколка $v_2$, подставив $v=u$ в соответствующую формулу:
$v_2 = \frac{u + u}{1 + u \cdot u / c^2} = \frac{2u}{1 + u^2/c^2}$
Ответ: Скорость частицы до распада $v = u$. Скорость второго осколка $v_2 = \frac{2u}{1 + u^2/c^2}$.
Другие задания:
Помогло решение? Оставьте отзыв в комментариях ниже.
Присоединяйтесь к Телеграм-группе @top_gdz
ПрисоединитьсяМы подготовили для вас ответ c подробным объяснением домашего задания по физике за 8-11 класс, для упражнения номер 21.4 расположенного на странице 128 к учебнику, задачнику 2005 года издания для учащихся школ и гимназий.
Теперь на нашем сайте ГДЗ.ТОП вы всегда легко и бесплатно найдёте условие с правильным ответом на вопрос «Как решить ДЗ» и «Как сделать» задание по физике к упражнению №21.4 (с. 128), авторов: Гельфгат (Илья Маркович), Генденштейн (Лев Элевич), Кирик (Леонид Анатольевич), учебного пособия издательства Илекса.