Номер 19, страница 24, часть 1 - гдз по физике 9 класс учебник Генденштейн, Булатова

Авторы: Генденштейн Л. Э., Булатова А. А., Корнильев И. Н., Кошкина А. В.

Тип: Учебник

Издательство: Бином

Год издания: 2016 - 2026

Часть: 1

Цвет обложки: бирюзовый

ISBN: 978-5-9963-3062-1

Часть 1. Механические явления. Глава I. Кинематика. Параграф 2. Прямолинейное равномерное движение - номер 19, страница 24.

App\Models\Task {#1030 // resources/views/models/task/default.blade.php
  #connection: "mysql"
  #table: "tasks"
  #primaryKey: "id"
  #keyType: "int"
  +incrementing: true
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  +preventsLazyLoading: false
  #perPage: 15
  +exists: true
  +wasRecentlyCreated: false
  #escapeWhenCastingToString: false
  #attributes: array:24 [
    "id" => 1433334
    "created_at" => "2026-04-10 13:58:26"
    "updated_at" => null
    "field_page_start" => "24"
    "field_page_end" => null
    "field_url" => "/9-klass/fizika/gendenshtejn-uchebnik/02-19"
    "field_display_title" => "19"
    "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"
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          #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
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            "name" => "номер"
            "field_cases" => array:6 [
              "field_accusative_case" => "номер"
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              "field_nominative_case" => "номер"
              "field_prepositional_case" => "номере"
            ]
            "field_short_name" => ""
          ]
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    "top_parent_branch" => Illuminate\Database\Eloquent\Collection {#1046
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        0 => App\Models\Branch {#1045
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          #table: "branches"
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          #keyType: "int"
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            "id" => 1433206
            "created_at" => "2026-04-10 13:58:26"
            "updated_at" => null
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                0 => App\Models\Term {#1047
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                  #primaryKey: "id"
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                    "id" => 31
                    "created_at" => "2026-04-10 13:58:26"
                    "updated_at" => null
                    "name" => "Часть"
                    "field_cases" => array:6 [ …6]
                    "field_page_check_not_needed" => "1"
                    "field_short_name" => "ч."
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              #items: array:1 [
                0 => App\Models\Book {#1049
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                  #table: "books"
                  #primaryKey: "id"
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                    "id" => 2980
                    "created_at" => "2026-04-10 13:58:26"
                    "updated_at" => null
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                        0 => App\Models\Term {#1048
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                          #table: "terms"
                          #primaryKey: "id"
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                            "id" => 6493
                            "created_at" => "2026-04-10 13:58:26"
                            "updated_at" => null
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                            "field_abbreviated_name" => null
                            "field_cases" => array:6 [ …6]
                            "field_foreign_lang_name" => null
                            "field_short_name" => null
                            "field_subject_type" => "technical_subject"
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                            "id" => 6493
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                            "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"
                          ]
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                    "field_class" => Illuminate\Database\Eloquent\Collection {#1052
                      #items: array:1 [
                        0 => App\Models\Term {#1053
                          #connection: "mysql"
                          #table: "terms"
                          #primaryKey: "id"
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                          #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 [
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                            "created_at" => "2026-04-10 13:58:26"
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                    "field_publisher" => Illuminate\Database\Eloquent\Collection {#1054
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                        0 => App\Models\Term {#1055
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                          #table: "terms"
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                          ]
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                      #items: array:4 [
                        0 => App\Models\Term {#1057
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                          #table: "terms"
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                            "created_at" => "2026-04-10 13:58:26"
                            "updated_at" => null
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                        1 => App\Models\Term {#1058
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                          #table: "terms"
                          #primaryKey: "id"
                          #keyType: "int"
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                            "created_at" => "2026-04-10 13:58:26"
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                            "field_foreign_lang_patronymic" => null
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                            "field_name" => "Альбина"
                            "field_patronymic" => "Александрова"
                            "field_surname_rp" => null
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                        2 => App\Models\Term {#1059
                          #connection: "mysql"
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                        3 => App\Models\Term {#1060
                          #connection: "mysql"
                          #table: "terms"
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                    "field_author_foreign" => Illuminate\Database\Eloquent\Collection {#1061
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                        0 => App\Models\Term {#1063
                          #connection: "mysql"
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                            "created_at" => "2026-04-10 13:58:26"
                            "updated_at" => null
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                            "field_plural_form" => null
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                    "field_country" => Illuminate\Database\Eloquent\Collection {#1064
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                        0 => App\Models\Term {#1065
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                          +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 {#1066
                      #items: array:1 [
                        0 => App\Models\Term {#1067
                          #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 {#1068
                      #items: []
                      #escapeWhenCastingToString: false
                    }
                    "field_umk" => Illuminate\Database\Eloquent\Collection {#1069
                      #items: []
                      #escapeWhenCastingToString: false
                    }
                    "field_level_of_education" => Illuminate\Database\Eloquent\Collection {#1070
                      #items: []
                      #escapeWhenCastingToString: false
                    }
                    "field_standart_of_education" => Illuminate\Database\Eloquent\Collection {#1071
                      #items: []
                      #escapeWhenCastingToString: false
                    }
                    "field_publication_number" => null
                    "field_publication_type" => Illuminate\Database\Eloquent\Collection {#1072
                      #items: []
                      #escapeWhenCastingToString: false
                    }
                    "field_under_the_edition" => Illuminate\Database\Eloquent\Collection {#1073
                      #items: array:1 [
                        0 => App\Models\Term {#1074
                          #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" => 5395
                            "created_at" => "2026-04-10 13:58:26"
                            "updated_at" => null
                            "name" => "Орлов"
                            "field_bio" => null
                            "field_degree_rp" => null
                            "field_foreign_lang_name" => null
                            "field_foreign_lang_patronymic" => null
                            "field_foreign_lang_surname" => null
                            "field_name" => "Владимир"
                            "field_patronymic" => "Алексеевич"
                            "field_surname_rp" => "Орлова"
                          ]
                          #original: array:12 [
                            "id" => 5395
                            "created_at" => "2026-04-10 13:58:26"
                            "updated_at" => null
                            "name" => "Орлов"
                            "field_bio" => null
                            "field_degree_rp" => null
                            "field_foreign_lang_name" => null
                            "field_foreign_lang_patronymic" => null
                            "field_foreign_lang_surname" => null
                            "field_name" => "Владимир"
                            "field_patronymic" => "Алексеевич"
                            "field_surname_rp" => "Орлова"
                          ]
                          #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_degree" => null
                    "field_cover_description" => null
                    "field_publication_year" => "2016"
                    "field_publication_year_until" => null
                    "field_part" => "1, 2"
                    "field_part_writing" => "Часть"
                    "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" => "1111"
                    "field_priority" => null
                    "field_default_folder" => "/fizika_09/gendenshtejn-u/"
                    "field_isbn" => "978-5-9963-3062-1"
                    "field_cover" => array:2 [
                      0 => "/media/fizika_09/gendenshtejn-u/covers/cover1.webp?ts=1759256052"
                      1 => "/media/fizika_09/gendenshtejn-u/covers/cover2.webp?ts=1759256052"
                    ]
                    "field_cover_alts" => array:2 [
                      0 => ""
                      1 => ""
                    ]
                    "field_covers" => array:2 [
                      0 => array:4 [
                        "path" => "/media/fizika_09/gendenshtejn-u/covers/cover1.webp?ts=1759256052"
                        "alt" => ""
                        "width" => "1863"
                        "height" => "2813"
                      ]
                      1 => array:4 [
                        "path" => "/media/fizika_09/gendenshtejn-u/covers/cover2.webp?ts=1759256052"
                        "alt" => ""
                        "width" => "1863"
                        "height" => "2809"
                      ]
                    ]
                    "field_popular_book" => "0"
                    "field_recommended_books" => Illuminate\Database\Eloquent\Collection {#1075
                      #items: []
                      #escapeWhenCastingToString: false
                    }
                    "field_new_book" => Illuminate\Database\Eloquent\Collection {#1076
                      #items: []
                      #escapeWhenCastingToString: false
                    }
                    "field_old_book" => Illuminate\Database\Eloquent\Collection {#1077
                      #items: []
                      #escapeWhenCastingToString: false
                    }
                    "field_url" => "/9-klass/fizika/gendenshtejn-uchebnik"
                    "field_cover_color" => Illuminate\Database\Eloquent\Collection {#1078
                      #items: array:1 [
                        0 => App\Models\Term {#1079
                          #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" => 6978
                            "created_at" => "2026-04-10 13:58:26"
                            "updated_at" => null
                            "name" => "бирюзовый"
                            "field_cases" => array:6 [ …6]
                            "field_translit" => "biruzovyy"
                          ]
                          #original: array:6 [
                            "id" => 6978
                            "created_at" => "2026-04-10 13:58:26"
                            "updated_at" => null
                            "name" => "бирюзовый"
                            "field_cases" => array:6 [ …6]
                            "field_translit" => "biruzovyy"
                          ]
                          #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" => 380
                      "subject" => 556
                      "class_subject" => 493
                    ]
                  ]
                  #original: array:50 [
                    "id" => 2980
                    "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 {#1051}
                    "field_class" => Illuminate\Database\Eloquent\Collection {#1052}
                    "field_publisher" => Illuminate\Database\Eloquent\Collection {#1054}
                    "field_author" => Illuminate\Database\Eloquent\Collection {#1056}
                    "field_author_foreign" => Illuminate\Database\Eloquent\Collection {#1061}
                    "field_book_type" => Illuminate\Database\Eloquent\Collection {#1062}
                    "field_country" => Illuminate\Database\Eloquent\Collection {#1064}
                    "field_city" => Illuminate\Database\Eloquent\Collection {#1066}
                    "field_series" => Illuminate\Database\Eloquent\Collection {#1068}
                    "field_umk" => Illuminate\Database\Eloquent\Collection {#1069}
                    "field_level_of_education" => Illuminate\Database\Eloquent\Collection {#1070}
                    "field_standart_of_education" => Illuminate\Database\Eloquent\Collection {#1071}
                    "field_publication_number" => null
                    "field_publication_type" => Illuminate\Database\Eloquent\Collection {#1072}
                    "field_under_the_edition" => Illuminate\Database\Eloquent\Collection {#1073}
                    "field_under_the_edition_degree" => null
                    "field_cover_description" => null
                    "field_publication_year" => "2016"
                    "field_publication_year_until" => null
                    "field_part" => "1, 2"
                    "field_part_writing" => "Часть"
                    "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" => "1111"
                    "field_priority" => null
                    "field_default_folder" => "/fizika_09/gendenshtejn-u/"
                    "field_isbn" => "978-5-9963-3062-1"
                    "field_cover" => array:2 [
                      0 => "/media/fizika_09/gendenshtejn-u/covers/cover1.webp?ts=1759256052"
                      1 => "/media/fizika_09/gendenshtejn-u/covers/cover2.webp?ts=1759256052"
                    ]
                    "field_cover_alts" => array:2 [
                      0 => ""
                      1 => ""
                    ]
                    "field_covers" => array:2 [
                      0 => array:4 [
                        "path" => "/media/fizika_09/gendenshtejn-u/covers/cover1.webp?ts=1759256052"
                        "alt" => ""
                        "width" => "1863"
                        "height" => "2813"
                      ]
                      1 => array:4 [
                        "path" => "/media/fizika_09/gendenshtejn-u/covers/cover2.webp?ts=1759256052"
                        "alt" => ""
                        "width" => "1863"
                        "height" => "2809"
                      ]
                    ]
                    "field_popular_book" => "0"
                    "field_recommended_books" => Illuminate\Database\Eloquent\Collection {#1075}
                    "field_new_book" => Illuminate\Database\Eloquent\Collection {#1076}
                    "field_old_book" => Illuminate\Database\Eloquent\Collection {#1077}
                    "field_url" => "/9-klass/fizika/gendenshtejn-uchebnik"
                    "field_cover_color" => Illuminate\Database\Eloquent\Collection {#1078}
                    "field_metatags_title" => null
                    "field_metatags_description" => null
                    "field_h1" => null
                    "field_description_top" => null
                    "field_description_bottom" => null
                    "breadcrumbs" => array:3 [
                      "class" => 380
                      "subject" => 556
                      "class_subject" => 493
                    ]
                  ]
                  #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 {#1080
              #items: []
              #escapeWhenCastingToString: false
            }
          ]
          #original: array:24 [
            "id" => 1433206
            "created_at" => "2026-04-10 13:58:26"
            "updated_at" => null
            "field_display_title" => null
            "field_branch_order" => "1"
            "field_url" => null
            "field_branch_type" => Illuminate\Database\Eloquent\Collection {#1050}
            "field_page_start" => "6"
            "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 {#1082}
            "branch_parent" => Illuminate\Database\Eloquent\Collection {#1080}
          ]
          #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 {#1189
      #items: array:4 [
        0 => App\Models\Branch {#1199
          #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" => 1433206
            "created_at" => "2026-04-10 13:58:26"
            "updated_at" => null
            "field_display_title" => null
            "field_branch_order" => "1"
            "field_url" => null
            "field_branch_type" => Illuminate\Database\Eloquent\Collection {#1200
              #items: array:1 [
                0 => App\Models\Term {#1047}
              ]
              #escapeWhenCastingToString: false
            }
            "field_page_start" => "6"
            "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 {#1201
              #items: array:1 [
                0 => App\Models\Book {#1049}
              ]
              #escapeWhenCastingToString: false
            }
            "branch_parent" => Illuminate\Database\Eloquent\Collection {#1202
              #items: []
              #escapeWhenCastingToString: false
            }
          ]
          #original: array:24 [
            "id" => 1433206
            "created_at" => "2026-04-10 13:58:26"
            "updated_at" => null
            "field_display_title" => null
            "field_branch_order" => "1"
            "field_url" => null
            "field_branch_type" => Illuminate\Database\Eloquent\Collection {#1200}
            "field_page_start" => "6"
            "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 {#1201}
            "branch_parent" => Illuminate\Database\Eloquent\Collection {#1202}
          ]
          #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 {#1203
          #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" => 1433207
            "created_at" => "2026-04-10 13:58:26"
            "updated_at" => null
            "field_display_title" => "Механические явления"
            "field_branch_order" => null
            "field_url" => null
            "field_branch_type" => Illuminate\Database\Eloquent\Collection {#1204
              #items: []
              #escapeWhenCastingToString: false
            }
            "field_page_start" => "6"
            "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 {#1205
              #items: array:1 [
                0 => App\Models\Book {#1049}
              ]
              #escapeWhenCastingToString: false
            }
            "branch_parent" => Illuminate\Database\Eloquent\Collection {#1206
              #items: array:1 [
                0 => App\Models\Branch {#1045}
              ]
              #escapeWhenCastingToString: false
            }
          ]
          #original: array:24 [
            "id" => 1433207
            "created_at" => "2026-04-10 13:58:26"
            "updated_at" => null
            "field_display_title" => "Механические явления"
            "field_branch_order" => null
            "field_url" => null
            "field_branch_type" => Illuminate\Database\Eloquent\Collection {#1204}
            "field_page_start" => "6"
            "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 {#1205}
            "branch_parent" => Illuminate\Database\Eloquent\Collection {#1206}
          ]
          #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 {#1207
          #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" => 1433208
            "created_at" => "2026-04-10 13:58:26"
            "updated_at" => null
            "field_display_title" => "Кинематика"
            "field_branch_order" => "I"
            "field_url" => null
            "field_branch_type" => Illuminate\Database\Eloquent\Collection {#1211
              #items: array:1 [
                0 => App\Models\Term {#1208
                  #connection: "mysql"
                  #table: "terms"
                  #primaryKey: "id"
                  #keyType: "int"
                  +incrementing: false
                  #with: []
                  #withCount: []
                  +preventsLazyLoading: false
                  #perPage: 15
                  +exists: true
                  +wasRecentlyCreated: false
                  #escapeWhenCastingToString: false
                  #attributes: array:7 [
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                    "created_at" => "2026-04-10 13:58:26"
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            "book" => Illuminate\Database\Eloquent\Collection {#1210
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                0 => App\Models\Branch {#1218
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                  #table: "branches"
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                  #keyType: "int"
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                    "field_branch_type" => Illuminate\Database\Eloquent\Collection {#1220 …2}
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                    "book" => Illuminate\Database\Eloquent\Collection {#1221 …2}
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                    "book" => Illuminate\Database\Eloquent\Collection {#1221 …2}
                    "branch_parent" => Illuminate\Database\Eloquent\Collection {#1222 …2}
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            "field_url" => null
            "field_branch_type" => Illuminate\Database\Eloquent\Collection {#1211}
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            "book" => Illuminate\Database\Eloquent\Collection {#1210}
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          ]
        }
        3 => App\Models\Branch {#1212
          #connection: "mysql"
          #table: "branches"
          #primaryKey: "id"
          #keyType: "int"
          +incrementing: true
          #with: []
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          #perPage: 15
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          #attributes: array:24 [
            "id" => 1433210
            "created_at" => "2026-04-10 13:58:26"
            "updated_at" => null
            "field_display_title" => "Прямолинейное равномерное движение"
            "field_branch_order" => "2"
            "field_url" => null
            "field_branch_type" => Illuminate\Database\Eloquent\Collection {#1216
              #items: array:1 [
                0 => App\Models\Term {#1209
                  #connection: "mysql"
                  #table: "terms"
                  #primaryKey: "id"
                  #keyType: "int"
                  +incrementing: false
                  #with: []
                  #withCount: []
                  +preventsLazyLoading: false
                  #perPage: 15
                  +exists: true
                  +wasRecentlyCreated: false
                  #escapeWhenCastingToString: false
                  #attributes: array:7 [
                    "id" => 32
                    "created_at" => "2026-04-10 13:58:26"
                    "updated_at" => null
                    "name" => "Параграф"
                    "field_cases" => array:6 [ …6]
                    "field_page_check_not_needed" => null
                    "field_short_name" => "§"
                  ]
                  #original: array:7 [
                    "id" => 32
                    "created_at" => "2026-04-10 13:58:26"
                    "updated_at" => null
                    "name" => "Параграф"
                    "field_cases" => array:6 [ …6]
                    "field_page_check_not_needed" => null
                    "field_short_name" => "§"
                  ]
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            "field_page_start" => "18"
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            "field_branch_cover" => []
            "field_branch_covers" => []
            "book" => Illuminate\Database\Eloquent\Collection {#1213
              #items: array:1 [
                0 => App\Models\Book {#1049}
              ]
              #escapeWhenCastingToString: false
            }
            "branch_parent" => Illuminate\Database\Eloquent\Collection {#1299
              #items: array:1 [
                0 => App\Models\Branch {#1215
                  #connection: "mysql"
                  #table: "branches"
                  #primaryKey: "id"
                  #keyType: "int"
                  +incrementing: true
                  #with: []
                  #withCount: []
                  +preventsLazyLoading: false
                  #perPage: 15
                  +exists: true
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                  #escapeWhenCastingToString: false
                  #attributes: array:24 [
                    "id" => 1433208
                    "created_at" => "2026-04-10 13:58:26"
                    "updated_at" => null
                    "field_display_title" => "Кинематика"
                    "field_branch_order" => "I"
                    "field_url" => null
                    "field_branch_type" => Illuminate\Database\Eloquent\Collection {#1223 …2}
                    "field_page_start" => "6"
                    "field_branch_display" => "0"
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                    "field_branch_title_in_content" => "0"
                    "field_navigation_title" => null
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                    "field_h1" => null
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                    "field_branch_cover" => []
                    "field_branch_covers" => []
                    "book" => Illuminate\Database\Eloquent\Collection {#1224 …2}
                    "branch_parent" => Illuminate\Database\Eloquent\Collection {#1256 …2}
                  ]
                  #original: array:24 [
                    "id" => 1433208
                    "created_at" => "2026-04-10 13:58:26"
                    "updated_at" => null
                    "field_display_title" => "Кинематика"
                    "field_branch_order" => "I"
                    "field_url" => null
                    "field_branch_type" => Illuminate\Database\Eloquent\Collection {#1223 …2}
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                    "field_branch_covers" => []
                    "book" => Illuminate\Database\Eloquent\Collection {#1224 …2}
                    "branch_parent" => Illuminate\Database\Eloquent\Collection {#1256 …2}
                  ]
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          #original: array:24 [
            "id" => 1433210
            "created_at" => "2026-04-10 13:58:26"
            "updated_at" => null
            "field_display_title" => "Прямолинейное равномерное движение"
            "field_branch_order" => "2"
            "field_url" => null
            "field_branch_type" => Illuminate\Database\Eloquent\Collection {#1216}
            "field_page_start" => "18"
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            "book" => Illuminate\Database\Eloquent\Collection {#1213}
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            0 => "*"
          ]
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      ]
      #escapeWhenCastingToString: false
    }
    "content" => Illuminate\Database\Eloquent\Collection {#1111
      #items: array:2 [
        0 => App\Models\Element {#1185
          #connection: "mysql"
          #table: "elements"
          #primaryKey: "id"
          #keyType: "int"
          +incrementing: true
          #with: []
          #withCount: []
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          #perPage: 15
          +exists: true
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          #escapeWhenCastingToString: false
          #attributes: array:7 [
            "id" => 1696075
            "created_at" => "2026-04-10 13:58:26"
            "updated_at" => null
            "edition" => Illuminate\Database\Eloquent\Collection {#1175
              #items: array:1 [
                0 => App\Models\Edition {#1183
                  #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" => 6168
                    "created_at" => "2026-04-10 13:58:26"
                    "updated_at" => null
                    "title" => "Условие"
                    "field_order" => "1"
                    "field_publisher" => Illuminate\Database\Eloquent\Collection {#1181 …2}
                    "field_content_type" => "free"
                    "field_content_mode" => "text, image"
                    "field_page_content_mode" => "image"
                    "field_content_text_checked" => "0"
                    "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 {#1179 …2}
                    "field_comment" => null
                    "field_similar_book" => Illuminate\Database\Eloquent\Collection {#1180 …2}
                    "field_process_formula" => "katex"
                    "field_edition_group" => Illuminate\Database\Eloquent\Collection {#1178 …2}
                    "field_content_source" => null
                  ]
                  #original: array:21 [
                    "id" => 6168
                    "created_at" => "2026-04-10 13:58:26"
                    "updated_at" => null
                    "title" => "Условие"
                    "field_order" => "1"
                    "field_publisher" => Illuminate\Database\Eloquent\Collection {#1181 …2}
                    "field_content_type" => "free"
                    "field_content_mode" => "text, image"
                    "field_page_content_mode" => "image"
                    "field_content_text_checked" => "0"
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                    "field_solution_author" => "Автор"
                    "field_moderator" => "stas"
                    "field_edition_type" => "statement"
                    "field_root_dir" => "0-"
                    "field_responsible" => Illuminate\Database\Eloquent\Collection {#1179 …2}
                    "field_comment" => null
                    "field_similar_book" => Illuminate\Database\Eloquent\Collection {#1180 …2}
                    "field_process_formula" => "katex"
                    "field_edition_group" => Illuminate\Database\Eloquent\Collection {#1178 …2}
                    "field_content_source" => null
                  ]
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                    0 => "*"
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              ]
              #escapeWhenCastingToString: false
            }
            "task" => array:2 [
              "refs" => "1433334"
              "type" => "task"
            ]
            "text" => "<p><strong>19.</strong> От пристани А до пристани B моторная лодка плыла 5 ч, а от пристани B до пристани А она плыла 3 ч. Расстояние между пристанями 15 км.</p><p><strong>а)</strong> Какая пристань находится выше по течению?</p><p><strong>б)</strong> Обозначьте $\text{d}$ расстояние между пристанями, $v_{\text{л}}$ — модуль скорости лодки относительно воды, $v_{\text{т}}$ — скорость течения, $t_{\text{AB}}$ — время движения лодки от A к B, $t_{\text{BA}}$ — время движения лодки от B к A. Запишите уравнения, описывающие движение лодки от A к B и от B к A.</p><p><strong>в)</strong> Используя полученную систему уравнений с двумя неизвестными, выразите скорость лодки относительно воды $v_{\text{л}}$ и скорость течения $v_{\text{т}}$ через $d, t_{\text{AB}}$ и $t_{\text{BA}}$.</p><p><strong>г)</strong> Найдите значения скорости лодки относительно воды и скорости течения.</p><p><strong>д)</strong> Сколько времени будет плыть плот от одной пристани до другой?</p>"
            "img" => array:1 [
              0 => array:5 [
                "name" => "19-1.jpg"
                "alt" => null
                "width" => "1568"
                "height" => 908
                "path" => "/media/fizika_09/gendenshtejn-u/0-02/19-1.webp?ts=1759348132"
              ]
            ]
          ]
          #original: array:7 [
            "id" => 1696075
            "created_at" => "2026-04-10 13:58:26"
            "updated_at" => null
            "edition" => Illuminate\Database\Eloquent\Collection {#1175}
            "task" => array:2 [
              "refs" => "1433334"
              "type" => "task"
            ]
            "text" => "<p><strong>19.</strong> От пристани А до пристани B моторная лодка плыла 5 ч, а от пристани B до пристани А она плыла 3 ч. Расстояние между пристанями 15 км.</p><p><strong>а)</strong> Какая пристань находится выше по течению?</p><p><strong>б)</strong> Обозначьте $\text{d}$ расстояние между пристанями, $v_{\text{л}}$ — модуль скорости лодки относительно воды, $v_{\text{т}}$ — скорость течения, $t_{\text{AB}}$ — время движения лодки от A к B, $t_{\text{BA}}$ — время движения лодки от B к A. Запишите уравнения, описывающие движение лодки от A к B и от B к A.</p><p><strong>в)</strong> Используя полученную систему уравнений с двумя неизвестными, выразите скорость лодки относительно воды $v_{\text{л}}$ и скорость течения $v_{\text{т}}$ через $d, t_{\text{AB}}$ и $t_{\text{BA}}$.</p><p><strong>г)</strong> Найдите значения скорости лодки относительно воды и скорости течения.</p><p><strong>д)</strong> Сколько времени будет плыть плот от одной пристани до другой?</p>"
            "img" => array:1 [
              0 => array:5 [
                "name" => "19-1.jpg"
                "alt" => null
                "width" => "1568"
                "height" => 908
                "path" => "/media/fizika_09/gendenshtejn-u/0-02/19-1.webp?ts=1759348132"
              ]
            ]
          ]
          #changes: []
          #casts: []
          #classCastCache: []
          #attributeCastCache: []
          #dateFormat: null
          #appends: []
          #dispatchesEvents: []
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          #touches: []
          +timestamps: true
          +usesUniqueIds: false
          #hidden: []
          #visible: []
          #fillable: []
          #guarded: array:1 [
            0 => "*"
          ]
        }
        1 => App\Models\Element {#1177
          #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" => 1780145
            "created_at" => "2026-04-10 13:58:26"
            "updated_at" => null
            "edition" => Illuminate\Database\Eloquent\Collection {#1167
              #items: array:1 [
                0 => App\Models\Edition {#1176
                  #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" => 6515
                    "created_at" => "2026-04-10 13:58:26"
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            "text" => "<p><strong>а)</strong> Так как время движения от пристани А до пристани В ($t_{AB} = 5$ ч) больше, чем время движения от В до А ($t_{BA} = 3$ ч), то скорость лодки на пути из А в В была меньше, чем на пути из В в А. Скорость движения уменьшается, когда лодка плывет против течения, и увеличивается, когда плывет по течению. Следовательно, из А в В лодка двигалась против течения, а из В в А — по течению. Это означает, что река течет в направлении от В к А, поэтому пристань В находится выше по течению.</p><p><strong>Ответ:</strong> Пристань В находится выше по течению.</p><p><strong>б)</strong> При движении лодки от А к В (против течения) ее скорость относительно берега равна разности скорости лодки относительно воды $v_л$ и скорости течения $v_т$. Расстояние $\text{d}$ равно произведению этой скорости на время движения $t_{AB}$.</p><p>$d = (v_л - v_т) \cdot t_{AB}$</p><p>При движении лодки от В к А (по течению) ее скорость относительно берега равна сумме скорости лодки относительно воды $v_л$ и скорости течения $v_т$. Расстояние $\text{d}$ равно произведению этой скорости на время движения $t_{BA}$.</p><p>$d = (v_л + v_т) \cdot t_{BA}$</p><p><strong>Ответ:</strong> Уравнение движения от А к В: $d = (v_л - v_т) \cdot t_{AB}$. Уравнение движения от В к А: $d = (v_л + v_т) \cdot t_{BA}$.</p><p><strong>в)</strong> Полученную систему уравнений можно переписать в виде:</p><p>$\begin{cases} v_л - v_т = \frac{d}{t_{AB}} \\ v_л + v_т = \frac{d}{t_{BA}} \end{cases}$</p><p>Чтобы выразить $v_л$, сложим оба уравнения системы:</p><p>$(v_л - v_т) + (v_л + v_т) = \frac{d}{t_{AB}} + \frac{d}{t_{BA}}$</p><p>$2v_л = d(\frac{1}{t_{AB}} + \frac{1}{t_{BA}}) = d \frac{t_{BA} + t_{AB}}{t_{AB}t_{BA}}$</p><p>$v_л = \frac{d(t_{AB} + t_{BA})}{2t_{AB}t_{BA}}$</p><p>Чтобы выразить $v_т$, вычтем первое уравнение из второго:</p><p>$(v_л + v_т) - (v_л - v_т) = \frac{d}{t_{BA}} - \frac{d}{t_{AB}}$</p><p>$2v_т = d(\frac{1}{t_{BA}} - \frac{1}{t_{AB}}) = d \frac{t_{AB} - t_{BA}}{t_{AB}t_{BA}}$</p><p>$v_т = \frac{d(t_{AB} - t_{BA})}{2t_{AB}t_{BA}}$</p><p><strong>Ответ:</strong> Скорость лодки относительно воды $v_л = \frac{d(t_{AB} + t_{BA})}{2t_{AB}t_{BA}}$, скорость течения $v_т = \frac{d(t_{AB} - t_{BA})}{2t_{AB}t_{BA}}$.</p><p><strong>г)</strong></p><p><strong>Дано:</strong></p><p>$d = 15$ км</p><p>$t_{AB} = 5$ ч</p><p>$t_{BA} = 3$ ч</p><p>В системе СИ:</p><p>$d = 15 \cdot 1000 \text{ м} = 15000 \text{ м}$</p><p>$t_{AB} = 5 \cdot 3600 \text{ с} = 18000 \text{ с}$</p><p>$t_{BA} = 3 \cdot 3600 \text{ с} = 10800 \text{ с}$</p><p><strong>Найти:</strong></p><p>$v_л$ - ?, $v_т$ - ?</p><p><strong>Решение:</strong></p><p>Для удобства расчетов используем исходные данные в км и часах, подставляя их в формулы, выведенные в пункте <strong>в)</strong>.</p><p>Скорость лодки относительно воды:</p><p>$v_л = \frac{15 \text{ км} \cdot (5 \text{ ч} + 3 \text{ ч})}{2 \cdot 5 \text{ ч} \cdot 3 \text{ ч}} = \frac{15 \cdot 8}{30} \frac{\text{км}}{\text{ч}} = \frac{120}{30} \frac{\text{км}}{\text{ч}} = 4$ км/ч.</p><p>Скорость течения:</p><p>$v_т = \frac{15 \text{ км} \cdot (5 \text{ ч} - 3 \text{ ч})}{2 \cdot 5 \text{ ч} \cdot 3 \text{ ч}} = \frac{15 \cdot 2}{30} \frac{\text{км}}{\text{ч}} = \frac{30}{30} \frac{\text{км}}{\text{ч}} = 1$ км/ч.</p><p><strong>Ответ:</strong> Скорость лодки относительно воды 4 км/ч, скорость течения 1 км/ч.</p><p><strong>д)</strong> Плот не имеет собственной скорости и движется со скоростью течения реки $v_т$. Плот может плыть только по течению, то есть от пристани В (расположенной выше по течению) к пристани А. Время движения плота $t_{плота}$ найдем по формуле:</p><p>$t_{плота} = \frac{d}{v_т}$</p><p>Подставим значения расстояния $\text{d}$ и скорости течения $v_т$, найденной в пункте <strong>г)</strong>:</p><p>$t_{плота} = \frac{15 \text{ км}}{1 \text{ км/ч}} = 15$ ч.</p><p><strong>Ответ:</strong> Плот будет плыть от одной пристани до другой 15 часов.</p>"
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            "text" => "<p><strong>а)</strong> Так как время движения от пристани А до пристани В ($t_{AB} = 5$ ч) больше, чем время движения от В до А ($t_{BA} = 3$ ч), то скорость лодки на пути из А в В была меньше, чем на пути из В в А. Скорость движения уменьшается, когда лодка плывет против течения, и увеличивается, когда плывет по течению. Следовательно, из А в В лодка двигалась против течения, а из В в А — по течению. Это означает, что река течет в направлении от В к А, поэтому пристань В находится выше по течению.</p><p><strong>Ответ:</strong> Пристань В находится выше по течению.</p><p><strong>б)</strong> При движении лодки от А к В (против течения) ее скорость относительно берега равна разности скорости лодки относительно воды $v_л$ и скорости течения $v_т$. Расстояние $\text{d}$ равно произведению этой скорости на время движения $t_{AB}$.</p><p>$d = (v_л - v_т) \cdot t_{AB}$</p><p>При движении лодки от В к А (по течению) ее скорость относительно берега равна сумме скорости лодки относительно воды $v_л$ и скорости течения $v_т$. Расстояние $\text{d}$ равно произведению этой скорости на время движения $t_{BA}$.</p><p>$d = (v_л + v_т) \cdot t_{BA}$</p><p><strong>Ответ:</strong> Уравнение движения от А к В: $d = (v_л - v_т) \cdot t_{AB}$. Уравнение движения от В к А: $d = (v_л + v_т) \cdot t_{BA}$.</p><p><strong>в)</strong> Полученную систему уравнений можно переписать в виде:</p><p>$\begin{cases} v_л - v_т = \frac{d}{t_{AB}} \\ v_л + v_т = \frac{d}{t_{BA}} \end{cases}$</p><p>Чтобы выразить $v_л$, сложим оба уравнения системы:</p><p>$(v_л - v_т) + (v_л + v_т) = \frac{d}{t_{AB}} + \frac{d}{t_{BA}}$</p><p>$2v_л = d(\frac{1}{t_{AB}} + \frac{1}{t_{BA}}) = d \frac{t_{BA} + t_{AB}}{t_{AB}t_{BA}}$</p><p>$v_л = \frac{d(t_{AB} + t_{BA})}{2t_{AB}t_{BA}}$</p><p>Чтобы выразить $v_т$, вычтем первое уравнение из второго:</p><p>$(v_л + v_т) - (v_л - v_т) = \frac{d}{t_{BA}} - \frac{d}{t_{AB}}$</p><p>$2v_т = d(\frac{1}{t_{BA}} - \frac{1}{t_{AB}}) = d \frac{t_{AB} - t_{BA}}{t_{AB}t_{BA}}$</p><p>$v_т = \frac{d(t_{AB} - t_{BA})}{2t_{AB}t_{BA}}$</p><p><strong>Ответ:</strong> Скорость лодки относительно воды $v_л = \frac{d(t_{AB} + t_{BA})}{2t_{AB}t_{BA}}$, скорость течения $v_т = \frac{d(t_{AB} - t_{BA})}{2t_{AB}t_{BA}}$.</p><p><strong>г)</strong></p><p><strong>Дано:</strong></p><p>$d = 15$ км</p><p>$t_{AB} = 5$ ч</p><p>$t_{BA} = 3$ ч</p><p>В системе СИ:</p><p>$d = 15 \cdot 1000 \text{ м} = 15000 \text{ м}$</p><p>$t_{AB} = 5 \cdot 3600 \text{ с} = 18000 \text{ с}$</p><p>$t_{BA} = 3 \cdot 3600 \text{ с} = 10800 \text{ с}$</p><p><strong>Найти:</strong></p><p>$v_л$ - ?, $v_т$ - ?</p><p><strong>Решение:</strong></p><p>Для удобства расчетов используем исходные данные в км и часах, подставляя их в формулы, выведенные в пункте <strong>в)</strong>.</p><p>Скорость лодки относительно воды:</p><p>$v_л = \frac{15 \text{ км} \cdot (5 \text{ ч} + 3 \text{ ч})}{2 \cdot 5 \text{ ч} \cdot 3 \text{ ч}} = \frac{15 \cdot 8}{30} \frac{\text{км}}{\text{ч}} = \frac{120}{30} \frac{\text{км}}{\text{ч}} = 4$ км/ч.</p><p>Скорость течения:</p><p>$v_т = \frac{15 \text{ км} \cdot (5 \text{ ч} - 3 \text{ ч})}{2 \cdot 5 \text{ ч} \cdot 3 \text{ ч}} = \frac{15 \cdot 2}{30} \frac{\text{км}}{\text{ч}} = \frac{30}{30} \frac{\text{км}}{\text{ч}} = 1$ км/ч.</p><p><strong>Ответ:</strong> Скорость лодки относительно воды 4 км/ч, скорость течения 1 км/ч.</p><p><strong>д)</strong> Плот не имеет собственной скорости и движется со скоростью течения реки $v_т$. Плот может плыть только по течению, то есть от пристани В (расположенной выше по течению) к пристани А. Время движения плота $t_{плота}$ найдем по формуле:</p><p>$t_{плота} = \frac{d}{v_т}$</p><p>Подставим значения расстояния $\text{d}$ и скорости течения $v_т$, найденной в пункте <strong>г)</strong>:</p><p>$t_{плота} = \frac{15 \text{ км}}{1 \text{ км/ч}} = 15$ ч.</p><p><strong>Ответ:</strong> Плот будет плыть от одной пристани до другой 15 часов.</p>"
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№19 (с. 24)
Условие. №19 (с. 24)
скриншот условия
Физика, 9 класс Учебник, авторы: Генденштейн Лев Элевич, Булатова Альбина Александрова, Корнильев Игорь Николаевич, Кошкина Анжелика Васильевна, издательство Бином, Москва, 2016, бирюзового цвета, Часть 1, страница 24, номер 19, Условие

19. От пристани А до пристани B моторная лодка плыла 5 ч, а от пристани B до пристани А она плыла 3 ч. Расстояние между пристанями 15 км.

а) Какая пристань находится выше по течению?

б) Обозначьте $\text{d}$ расстояние между пристанями, $v_{\text{л}}$ — модуль скорости лодки относительно воды, $v_{\text{т}}$ — скорость течения, $t_{\text{AB}}$ — время движения лодки от A к B, $t_{\text{BA}}$ — время движения лодки от B к A. Запишите уравнения, описывающие движение лодки от A к B и от B к A.

в) Используя полученную систему уравнений с двумя неизвестными, выразите скорость лодки относительно воды $v_{\text{л}}$ и скорость течения $v_{\text{т}}$ через $d, t_{\text{AB}}$ и $t_{\text{BA}}$.

г) Найдите значения скорости лодки относительно воды и скорости течения.

д) Сколько времени будет плыть плот от одной пристани до другой?

Решение. №19 (с. 24)

а) Так как время движения от пристани А до пристани В ($t_{AB} = 5$ ч) больше, чем время движения от В до А ($t_{BA} = 3$ ч), то скорость лодки на пути из А в В была меньше, чем на пути из В в А. Скорость движения уменьшается, когда лодка плывет против течения, и увеличивается, когда плывет по течению. Следовательно, из А в В лодка двигалась против течения, а из В в А — по течению. Это означает, что река течет в направлении от В к А, поэтому пристань В находится выше по течению.

Ответ: Пристань В находится выше по течению.

б) При движении лодки от А к В (против течения) ее скорость относительно берега равна разности скорости лодки относительно воды $v_л$ и скорости течения $v_т$. Расстояние $\text{d}$ равно произведению этой скорости на время движения $t_{AB}$.

$d = (v_л - v_т) \cdot t_{AB}$

При движении лодки от В к А (по течению) ее скорость относительно берега равна сумме скорости лодки относительно воды $v_л$ и скорости течения $v_т$. Расстояние $\text{d}$ равно произведению этой скорости на время движения $t_{BA}$.

$d = (v_л + v_т) \cdot t_{BA}$

Ответ: Уравнение движения от А к В: $d = (v_л - v_т) \cdot t_{AB}$. Уравнение движения от В к А: $d = (v_л + v_т) \cdot t_{BA}$.

в) Полученную систему уравнений можно переписать в виде:

$\begin{cases} v_л - v_т = \frac{d}{t_{AB}} \\ v_л + v_т = \frac{d}{t_{BA}} \end{cases}$

Чтобы выразить $v_л$, сложим оба уравнения системы:

$(v_л - v_т) + (v_л + v_т) = \frac{d}{t_{AB}} + \frac{d}{t_{BA}}$

$2v_л = d(\frac{1}{t_{AB}} + \frac{1}{t_{BA}}) = d \frac{t_{BA} + t_{AB}}{t_{AB}t_{BA}}$

$v_л = \frac{d(t_{AB} + t_{BA})}{2t_{AB}t_{BA}}$

Чтобы выразить $v_т$, вычтем первое уравнение из второго:

$(v_л + v_т) - (v_л - v_т) = \frac{d}{t_{BA}} - \frac{d}{t_{AB}}$

$2v_т = d(\frac{1}{t_{BA}} - \frac{1}{t_{AB}}) = d \frac{t_{AB} - t_{BA}}{t_{AB}t_{BA}}$

$v_т = \frac{d(t_{AB} - t_{BA})}{2t_{AB}t_{BA}}$

Ответ: Скорость лодки относительно воды $v_л = \frac{d(t_{AB} + t_{BA})}{2t_{AB}t_{BA}}$, скорость течения $v_т = \frac{d(t_{AB} - t_{BA})}{2t_{AB}t_{BA}}$.

г)

Дано:

$d = 15$ км

$t_{AB} = 5$ ч

$t_{BA} = 3$ ч

В системе СИ:

$d = 15 \cdot 1000 \text{ м} = 15000 \text{ м}$

$t_{AB} = 5 \cdot 3600 \text{ с} = 18000 \text{ с}$

$t_{BA} = 3 \cdot 3600 \text{ с} = 10800 \text{ с}$

Найти:

$v_л$ - ?, $v_т$ - ?

Решение:

Для удобства расчетов используем исходные данные в км и часах, подставляя их в формулы, выведенные в пункте в).

Скорость лодки относительно воды:

$v_л = \frac{15 \text{ км} \cdot (5 \text{ ч} + 3 \text{ ч})}{2 \cdot 5 \text{ ч} \cdot 3 \text{ ч}} = \frac{15 \cdot 8}{30} \frac{\text{км}}{\text{ч}} = \frac{120}{30} \frac{\text{км}}{\text{ч}} = 4$ км/ч.

Скорость течения:

$v_т = \frac{15 \text{ км} \cdot (5 \text{ ч} - 3 \text{ ч})}{2 \cdot 5 \text{ ч} \cdot 3 \text{ ч}} = \frac{15 \cdot 2}{30} \frac{\text{км}}{\text{ч}} = \frac{30}{30} \frac{\text{км}}{\text{ч}} = 1$ км/ч.

Ответ: Скорость лодки относительно воды 4 км/ч, скорость течения 1 км/ч.

д) Плот не имеет собственной скорости и движется со скоростью течения реки $v_т$. Плот может плыть только по течению, то есть от пристани В (расположенной выше по течению) к пристани А. Время движения плота $t_{плота}$ найдем по формуле:

$t_{плота} = \frac{d}{v_т}$

Подставим значения расстояния $\text{d}$ и скорости течения $v_т$, найденной в пункте г):

$t_{плота} = \frac{15 \text{ км}}{1 \text{ км/ч}} = 15$ ч.

Ответ: Плот будет плыть от одной пристани до другой 15 часов.

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