Номер 2, страница 78 - гдз по физике 8 класс учебник Пёрышкин

Физика, 8 класс Учебник, автор: Пёрышкин И М, издательство Просвещение, Москва, 2023, белого цвета

Авторы: Пёрышкин И. М.

Тип: Учебник

Издательство: Просвещение

Год издания: 2023 - 2026

Уровень обучения: базовый

Цвет обложки: белый с градусником

ISBN: 978-5-09-102555-2

Допущено Министерством просвещения Российской Федерации

Глава 1. Тепловые явления. Параграф 20. Влажность воздуха. Способы определения влажности воздуха. Задание 13 - номер 2, страница 78.

App\Models\Task {#1024 // resources/views/models/task/default.blade.php
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                            "name" => "Просвещение"
                            "field_cases" => null
                            "field_translit" => "prosveschenie"
                          ]
                          #original: array:6 [
                            "id" => 5153
                            "created_at" => "2026-04-10 13:58:26"
                            "updated_at" => null
                            "name" => "Просвещение"
                            "field_cases" => null
                            "field_translit" => "prosveschenie"
                          ]
                          #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 {#1076
                      #items: array:1 [
                        0 => App\Models\Term {#1077
                          #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" => 6884
                            "created_at" => "2026-04-10 13:58:26"
                            "updated_at" => null
                            "name" => "Пёрышкин"
                            "field_bio" => null
                            "field_degree_rp" => null
                            "field_foreign_lang_name" => null
                            "field_foreign_lang_patronymic" => null
                            "field_foreign_lang_surname" => null
                            "field_name" => "И"
                            "field_patronymic" => "М"
                            "field_surname_rp" => null
                          ]
                          #original: array:12 [
                            "id" => 6884
                            "created_at" => "2026-04-10 13:58:26"
                            "updated_at" => null
                            "name" => "Пёрышкин"
                            "field_bio" => null
                            "field_degree_rp" => null
                            "field_foreign_lang_name" => null
                            "field_foreign_lang_patronymic" => null
                            "field_foreign_lang_surname" => null
                            "field_name" => "И"
                            "field_patronymic" => "М"
                            "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 {#1078
                      #items: []
                      #escapeWhenCastingToString: false
                    }
                    "field_book_type" => Illuminate\Database\Eloquent\Collection {#1079
                      #items: array:1 [
                        0 => App\Models\Term {#1080
                          #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" => 6671
                            "created_at" => "2026-04-10 13:58:26"
                            "updated_at" => null
                            "name" => "Учебник"
                            "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"
                          ]
                          #original: array:10 [
                            "id" => 6671
                            "created_at" => "2026-04-10 13:58:26"
                            "updated_at" => null
                            "name" => "Учебник"
                            "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"
                          ]
                          #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 {#1081
                      #items: array:1 [
                        0 => App\Models\Term {#1082
                          #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 {#1083
                      #items: array:1 [
                        0 => App\Models\Term {#1084
                          #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
                             …3
                          ]
                          #changes: []
                          #casts: []
                          #classCastCache: []
                          #attributeCastCache: []
                          #dateFormat: null
                          #appends: []
                          #dispatchesEvents: []
                          #observables: []
                          #relations: []
                          #touches: []
                          +timestamps: true
                          +usesUniqueIds: false
                          #hidden: []
                          #visible: []
                          #fillable: []
                          #guarded: array:1 [ …1]
                        }
                      ]
                      #escapeWhenCastingToString: false
                    }
                    "field_series" => Illuminate\Database\Eloquent\Collection {#1085
                      #items: []
                      #escapeWhenCastingToString: false
                    }
                    "field_umk" => Illuminate\Database\Eloquent\Collection {#1086
                      #items: []
                      #escapeWhenCastingToString: false
                    }
                    "field_level_of_education" => Illuminate\Database\Eloquent\Collection {#1087
                      #items: array:1 [
                        0 => App\Models\Term {#1088
                          #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 [ …6]
                          #original: array:6 [ …6]
                          #changes: []
                          #casts: []
                          #classCastCache: []
                          #attributeCastCache: []
                          #dateFormat: null
                          #appends: []
                          #dispatchesEvents: []
                          #observables: []
                          #relations: []
                          #touches: []
                          +timestamps: true
                          +usesUniqueIds: false
                          #hidden: []
                          #visible: []
                          #fillable: []
                          #guarded: array:1 [ …1]
                        }
                      ]
                      #escapeWhenCastingToString: false
                    }
                    "field_standart_of_education" => Illuminate\Database\Eloquent\Collection {#1089
                      #items: array:1 [
                        0 => App\Models\Term {#1090
                          #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 [ …10]
                          #original: array:10 [ …10]
                          #changes: []
                          #casts: []
                          #classCastCache: []
                          #attributeCastCache: []
                          #dateFormat: null
                          #appends: []
                          #dispatchesEvents: []
                          #observables: []
                          #relations: []
                          #touches: []
                          +timestamps: true
                          +usesUniqueIds: false
                          #hidden: []
                          #visible: []
                          #fillable: []
                          #guarded: array:1 [ …1]
                        }
                      ]
                      #escapeWhenCastingToString: false
                    }
                    "field_publication_number" => "3"
                    "field_publication_type" => Illuminate\Database\Eloquent\Collection {#1091
                      #items: array:1 [
                        0 => App\Models\Term {#1092
                          #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 [ …6]
                          #original: array:6 [ …6]
                          #changes: []
                          #casts: []
                          #classCastCache: []
                          #attributeCastCache: []
                          #dateFormat: null
                          #appends: []
                          #dispatchesEvents: []
                          #observables: []
                          #relations: []
                          #touches: []
                          +timestamps: true
                          +usesUniqueIds: false
                          #hidden: []
                          #visible: []
                          #fillable: []
                          #guarded: array:1 [ …1]
                        }
                      ]
                      #escapeWhenCastingToString: false
                    }
                    "field_under_the_edition" => Illuminate\Database\Eloquent\Collection {#1093
                      #items: []
                      #escapeWhenCastingToString: false
                    }
                    "field_under_the_edition_degree" => null
                    "field_cover_description" => "с градусником"
                    "field_publication_year" => "2023"
                    "field_publication_year_until" => null
                    "field_part" => ""
                    "field_part_writing" => ""
                    "field_second_foreign_language" => null
                    "field_for_whom" => null
                    "field_allowed" => "Допущено Министерством просвещения Российской Федерации"
                    "field_reserve_field" => null
                    "field_link_to_source" => null
                    "field_tasks_count" => "706"
                    "field_priority" => "2"
                    "field_default_folder" => "/fizika_08/Peryshkin-u23/"
                    "field_isbn" => "978-5-09-102555-2"
                    "field_cover" => array:1 [
                      0 => "/media/fizika_08/Peryshkin-u23/covers/cover1.webp?ts=1737917825"
                    ]
                    "field_cover_alts" => array:1 [
                      0 => ""
                    ]
                    "field_covers" => array:1 [
                      0 => array:4 [
                        "path" => "/media/fizika_08/Peryshkin-u23/covers/cover1.webp?ts=1737917825"
                        "alt" => ""
                        "width" => "1350"
                        "height" => "1772"
                      ]
                    ]
                    "field_popular_book" => null
                    "field_recommended_books" => Illuminate\Database\Eloquent\Collection {#1094
                      #items: []
                      #escapeWhenCastingToString: false
                    }
                    "field_new_book" => Illuminate\Database\Eloquent\Collection {#1095
                      #items: []
                      #escapeWhenCastingToString: false
                    }
                    "field_old_book" => Illuminate\Database\Eloquent\Collection {#1096
                      #items: []
                      #escapeWhenCastingToString: false
                    }
                    "field_url" => "/8-klass/fizika/peryshkin-uchebnik"
                    "field_cover_color" => Illuminate\Database\Eloquent\Collection {#1097
                      #items: array:1 [
                        0 => App\Models\Term {#1098
                          #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 [ …6]
                          #original: array:6 [ …6]
                          #changes: []
                          #casts: []
                          #classCastCache: []
                          #attributeCastCache: []
                          #dateFormat: null
                          #appends: []
                          #dispatchesEvents: []
                          #observables: []
                          #relations: []
                          #touches: []
                          +timestamps: true
                          +usesUniqueIds: false
                          #hidden: []
                          #visible: []
                          #fillable: []
                          #guarded: array:1 [ …1]
                        }
                      ]
                      #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" => 51
                    "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 {#1070}
                    "field_class" => Illuminate\Database\Eloquent\Collection {#1072}
                    "field_publisher" => Illuminate\Database\Eloquent\Collection {#1074}
                    "field_author" => Illuminate\Database\Eloquent\Collection {#1076}
                    "field_author_foreign" => Illuminate\Database\Eloquent\Collection {#1078}
                    "field_book_type" => Illuminate\Database\Eloquent\Collection {#1079}
                    "field_country" => Illuminate\Database\Eloquent\Collection {#1081}
                    "field_city" => Illuminate\Database\Eloquent\Collection {#1083}
                    "field_series" => Illuminate\Database\Eloquent\Collection {#1085}
                    "field_umk" => Illuminate\Database\Eloquent\Collection {#1086}
                    "field_level_of_education" => Illuminate\Database\Eloquent\Collection {#1087}
                    "field_standart_of_education" => Illuminate\Database\Eloquent\Collection {#1089}
                    "field_publication_number" => "3"
                    "field_publication_type" => Illuminate\Database\Eloquent\Collection {#1091}
                    "field_under_the_edition" => Illuminate\Database\Eloquent\Collection {#1093}
                    "field_under_the_edition_degree" => null
                    "field_cover_description" => "с градусником"
                    "field_publication_year" => "2023"
                    "field_publication_year_until" => null
                    "field_part" => ""
                    "field_part_writing" => ""
                    "field_second_foreign_language" => null
                    "field_for_whom" => null
                    "field_allowed" => "Допущено Министерством просвещения Российской Федерации"
                    "field_reserve_field" => null
                    "field_link_to_source" => null
                    "field_tasks_count" => "706"
                    "field_priority" => "2"
                    "field_default_folder" => "/fizika_08/Peryshkin-u23/"
                    "field_isbn" => "978-5-09-102555-2"
                    "field_cover" => array:1 [
                      0 => "/media/fizika_08/Peryshkin-u23/covers/cover1.webp?ts=1737917825"
                    ]
                    "field_cover_alts" => array:1 [
                      0 => ""
                    ]
                    "field_covers" => array:1 [
                      0 => array:4 [
                        "path" => "/media/fizika_08/Peryshkin-u23/covers/cover1.webp?ts=1737917825"
                        "alt" => ""
                        "width" => "1350"
                        "height" => "1772"
                      ]
                    ]
                    "field_popular_book" => null
                    "field_recommended_books" => Illuminate\Database\Eloquent\Collection {#1094}
                    "field_new_book" => Illuminate\Database\Eloquent\Collection {#1095}
                    "field_old_book" => Illuminate\Database\Eloquent\Collection {#1096}
                    "field_url" => "/8-klass/fizika/peryshkin-uchebnik"
                    "field_cover_color" => Illuminate\Database\Eloquent\Collection {#1097}
                    "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 {#1099
              #items: []
              #escapeWhenCastingToString: false
            }
          ]
          #original: array:24 [
            "id" => 598563
            "created_at" => "2026-04-10 13:58:26"
            "updated_at" => null
            "field_display_title" => "Тепловые явления"
            "field_branch_order" => "1"
            "field_url" => null
            "field_branch_type" => Illuminate\Database\Eloquent\Collection {#1066}
            "field_page_start" => "3"
            "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 {#1068}
            "branch_parent" => Illuminate\Database\Eloquent\Collection {#1099}
          ]
          #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 {#1100
          #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" => 598635
            "created_at" => "2026-04-10 13:58:26"
            "updated_at" => null
            "field_display_title" => "Влажность воздуха. Способы определения влажности воздуха"
            "field_branch_order" => "20"
            "field_url" => null
            "field_branch_type" => Illuminate\Database\Eloquent\Collection {#1101
              #items: array:1 [
                0 => App\Models\Term {#1102
                  #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" => "§"
                  ]
                  #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_page_start" => "73"
            "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
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            "field_description_bottom" => null
            "field_branch_cover" => []
            "field_branch_covers" => []
            "book" => Illuminate\Database\Eloquent\Collection {#1103
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                0 => App\Models\Book {#1069}
              ]
              #escapeWhenCastingToString: false
            }
            "branch_parent" => Illuminate\Database\Eloquent\Collection {#1104
              #items: array:1 [
                0 => App\Models\Branch {#1023}
              ]
              #escapeWhenCastingToString: false
            }
          ]
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            "id" => 598635
            "created_at" => "2026-04-10 13:58:26"
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            "field_display_title" => "Влажность воздуха. Способы определения влажности воздуха"
            "field_branch_order" => "20"
            "field_url" => null
            "field_branch_type" => Illuminate\Database\Eloquent\Collection {#1101}
            "field_page_start" => "73"
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            "field_display_branch_page" => "1"
            "field_branch_title_in_content" => "0"
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            "field_branch_cover" => []
            "field_branch_covers" => []
            "book" => Illuminate\Database\Eloquent\Collection {#1103}
            "branch_parent" => Illuminate\Database\Eloquent\Collection {#1104}
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          #visible: []
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          #guarded: array:1 [
            0 => "*"
          ]
        }
        2 => App\Models\Branch {#1105
          #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" => 598639
            "created_at" => "2026-04-10 13:58:26"
            "updated_at" => null
            "field_display_title" => "Задание 13"
            "field_branch_order" => null
            "field_url" => null
            "field_branch_type" => Illuminate\Database\Eloquent\Collection {#1106
              #items: []
              #escapeWhenCastingToString: false
            }
            "field_page_start" => "78"
            "field_branch_display" => "0"
            "field_branch_expanded" => "0"
            "field_display_branch_in_title" => "1"
            "field_display_task_interval" => "0"
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            "field_description_bottom" => null
            "field_branch_cover" => []
            "field_branch_covers" => []
            "book" => Illuminate\Database\Eloquent\Collection {#1107
              #items: array:1 [
                0 => App\Models\Book {#1069}
              ]
              #escapeWhenCastingToString: false
            }
            "branch_parent" => Illuminate\Database\Eloquent\Collection {#1108
              #items: array:1 [
                0 => App\Models\Branch {#1109
                  #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" => 598635
                    "created_at" => "2026-04-10 13:58:26"
                    "updated_at" => null
                    "field_display_title" => "Влажность воздуха. Способы определения влажности воздуха"
                    "field_branch_order" => "20"
                    "field_url" => null
                    "field_branch_type" => Illuminate\Database\Eloquent\Collection {#1110 …2}
                    "field_page_start" => "73"
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                    "field_branch_covers" => []
                    "book" => Illuminate\Database\Eloquent\Collection {#1111 …2}
                    "branch_parent" => Illuminate\Database\Eloquent\Collection {#1112 …2}
                  ]
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                    "field_display_title" => "Влажность воздуха. Способы определения влажности воздуха"
                    "field_branch_order" => "20"
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                    "field_branch_type" => Illuminate\Database\Eloquent\Collection {#1110 …2}
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                    "field_branch_cover" => []
                    "field_branch_covers" => []
                    "book" => Illuminate\Database\Eloquent\Collection {#1111 …2}
                    "branch_parent" => Illuminate\Database\Eloquent\Collection {#1112 …2}
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                    0 => "*"
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            "field_page_start" => "78"
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            "book" => Illuminate\Database\Eloquent\Collection {#1107}
            "branch_parent" => Illuminate\Database\Eloquent\Collection {#1108}
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            0 => "*"
          ]
        }
      ]
      #escapeWhenCastingToString: false
    }
    "content" => Illuminate\Database\Eloquent\Collection {#1113
      #items: array:4 [
        0 => App\Models\Element {#1114
          #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" => 745462
            "created_at" => "2026-04-10 13:58:26"
            "updated_at" => null
            "edition" => Illuminate\Database\Eloquent\Collection {#1115
              #items: array:1 [
                0 => App\Models\Edition {#1116
                  #connection: "mysql"
                  #table: "editions"
                  #primaryKey: "id"
                  #keyType: "int"
                  +incrementing: false
                  #with: []
                  #withCount: []
                  +preventsLazyLoading: false
                  #perPage: 15
                  +exists: true
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                  #escapeWhenCastingToString: false
                  #attributes: array:21 [
                    "id" => 1636
                    "created_at" => "2026-04-10 13:58:26"
                    "updated_at" => null
                    "title" => "Условие"
                    "field_order" => "1"
                    "field_publisher" => Illuminate\Database\Eloquent\Collection {#1117 …2}
                    "field_content_type" => "free"
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                    "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 {#1119 …2}
                    "field_comment" => null
                    "field_similar_book" => Illuminate\Database\Eloquent\Collection {#1120 …2}
                    "field_process_formula" => ""
                    "field_edition_group" => Illuminate\Database\Eloquent\Collection {#1121 …2}
                    "field_content_source" => null
                  ]
                  #original: array:21 [
                    "id" => 1636
                    "created_at" => "2026-04-10 13:58:26"
                    "updated_at" => null
                    "title" => "Условие"
                    "field_order" => "1"
                    "field_publisher" => Illuminate\Database\Eloquent\Collection {#1117 …2}
                    "field_content_type" => "free"
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                  ]
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            "task" => array:2 [
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            "text" => """
              <p><strong>2</strong>. Придумайте несколько задач, используя данные таблиц 5 и 6. Обменяйтесь с товарищем условиями задач и решите их.</p><figure><figure class="align-center">\n
               <img src="/media/fizika_08/Peryshkin-u23/0-20-4/2.webp?ts=1743615324" alt="Придумать несколько задач, используя данные таблиц 5 и 6" loading="lazy" width="1649" height="667">\n
               </figure>\n
              <figcaption> </figcaption></figure><figure><figure class="align-center">\n
               <img src="/media/fizika_08/Peryshkin-u23/0-20-4/2_0.webp?ts=1743615324" alt="Придумать несколько задач, используя данные таблиц 5 и 6" loading="lazy" width="1646" height="1283">\n
               </figure>\n
              <figcaption> </figcaption></figure>
              """
            "img" => array:1 [
              0 => array:5 [
                "name" => "2-1.png"
                "alt" => null
                "width" => "733"
                "height" => 97
                "path" => "/media/fizika_08/Peryshkin-u23/0-20-4/2-1.webp?ts=1738080879"
              ]
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            "id" => 745462
            "created_at" => "2026-04-10 13:58:26"
            "updated_at" => null
            "edition" => Illuminate\Database\Eloquent\Collection {#1115}
            "task" => array:2 [
              "refs" => "599013"
              "type" => "task"
            ]
            "text" => """
              <p><strong>2</strong>. Придумайте несколько задач, используя данные таблиц 5 и 6. Обменяйтесь с товарищем условиями задач и решите их.</p><figure><figure class="align-center">\n
               <img src="/media/fizika_08/Peryshkin-u23/0-20-4/2.webp?ts=1743615324" alt="Придумать несколько задач, используя данные таблиц 5 и 6" loading="lazy" width="1649" height="667">\n
               </figure>\n
              <figcaption> </figcaption></figure><figure><figure class="align-center">\n
               <img src="/media/fizika_08/Peryshkin-u23/0-20-4/2_0.webp?ts=1743615324" alt="Придумать несколько задач, используя данные таблиц 5 и 6" loading="lazy" width="1646" height="1283">\n
               </figure>\n
              <figcaption> </figcaption></figure>
              """
            "img" => array:1 [
              0 => array:5 [
                "name" => "2-1.png"
                "alt" => null
                "width" => "733"
                "height" => 97
                "path" => "/media/fizika_08/Peryshkin-u23/0-20-4/2-1.webp?ts=1738080879"
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          ]
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          #fillable: []
          #guarded: array:1 [
            0 => "*"
          ]
        }
        1 => App\Models\Element {#1122
          #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" => 745623
            "created_at" => "2026-04-10 13:58:26"
            "updated_at" => null
            "edition" => Illuminate\Database\Eloquent\Collection {#1123
              #items: array:1 [
                0 => App\Models\Edition {#1124
                  #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" => 1637
                    "created_at" => "2026-04-10 13:58:26"
                    "updated_at" => null
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                    "field_publisher" => Illuminate\Database\Eloquent\Collection {#1125 …2}
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                    "field_moderator" => "stas"
                    "field_edition_type" => "solution"
                    "field_root_dir" => "1-"
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                    "field_similar_book" => Illuminate\Database\Eloquent\Collection {#1128 …2}
                    "field_process_formula" => ""
                    "field_edition_group" => Illuminate\Database\Eloquent\Collection {#1129 …2}
                    "field_content_source" => null
                  ]
                  #original: array:21 [
                    "id" => 1637
                    "created_at" => "2026-04-10 13:58:26"
                    "updated_at" => null
                    "title" => "Решение 1"
                    "field_order" => "2"
                    "field_publisher" => Illuminate\Database\Eloquent\Collection {#1125 …2}
                    "field_content_type" => "free"
                    "field_content_mode" => "image"
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                    "field_moderator" => "stas"
                    "field_edition_type" => "solution"
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                    "field_comment" => null
                    "field_similar_book" => Illuminate\Database\Eloquent\Collection {#1128 …2}
                    "field_process_formula" => ""
                    "field_edition_group" => Illuminate\Database\Eloquent\Collection {#1129 …2}
                    "field_content_source" => null
                  ]
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                  #attributeCastCache: []
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                  +timestamps: true
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                  #guarded: array:1 [
                    0 => "*"
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                }
              ]
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            "task" => array:2 [
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            "img" => array:1 [
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                "alt" => null
                "width" => "2064"
                "height" => 2255
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          ]
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            "id" => 745623
            "created_at" => "2026-04-10 13:58:26"
            "updated_at" => null
            "edition" => Illuminate\Database\Eloquent\Collection {#1123}
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              "type" => "task"
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                "name" => "2-1.jpg"
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                "width" => "2064"
                "height" => 2255
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            0 => "*"
          ]
        }
        2 => App\Models\Element {#1130
          #connection: "mysql"
          #table: "elements"
          #primaryKey: "id"
          #keyType: "int"
          +incrementing: true
          #with: []
          #withCount: []
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          #perPage: 15
          +exists: true
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          #attributes: array:6 [
            "id" => 746981
            "created_at" => "2026-04-10 13:58:26"
            "updated_at" => null
            "edition" => Illuminate\Database\Eloquent\Collection {#1131
              #items: array:1 [
                0 => App\Models\Edition {#1132
                  #connection: "mysql"
                  #table: "editions"
                  #primaryKey: "id"
                  #keyType: "int"
                  +incrementing: false
                  #with: []
                  #withCount: []
                  +preventsLazyLoading: false
                  #perPage: 15
                  +exists: true
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                  #attributes: array:21 [
                    "id" => 1639
                    "created_at" => "2026-04-10 13:58:26"
                    "updated_at" => null
                    "title" => "Решение 3"
                    "field_order" => "4"
                    "field_publisher" => Illuminate\Database\Eloquent\Collection {#1133 …2}
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                    "field_page_content_text_checked" => "0"
                    "field_solution_author" => "Неизвестный"
                    "field_moderator" => "stas"
                    "field_edition_type" => "solution"
                    "field_root_dir" => "2-"
                    "field_responsible" => Illuminate\Database\Eloquent\Collection {#1135 …2}
                    "field_comment" => null
                    "field_similar_book" => Illuminate\Database\Eloquent\Collection {#1136 …2}
                    "field_process_formula" => ""
                    "field_edition_group" => Illuminate\Database\Eloquent\Collection {#1137 …2}
                    "field_content_source" => null
                  ]
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                    "id" => 1639
                    "created_at" => "2026-04-10 13:58:26"
                    "updated_at" => null
                    "title" => "Решение 3"
                    "field_order" => "4"
                    "field_publisher" => Illuminate\Database\Eloquent\Collection {#1133 …2}
                    "field_content_type" => "free"
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                    "field_page_content_text_checked" => "0"
                    "field_solution_author" => "Неизвестный"
                    "field_moderator" => "stas"
                    "field_edition_type" => "solution"
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            "text" => "<p>Поскольку в задании не предоставлены таблицы 5 и 6, в качестве примера создадим их и на их основе составим и решим две задачи.</p><p><strong>Таблица 5. Плотность некоторых веществ (при н.у.)</strong></p><table border="1" style="border-collapse: collapse; width: 100%;"><thead><tr style="background-color: #f2f2f2;"><th style="padding: 8px; text-align: left;">Вещество</th><th style="padding: 8px; text-align: left;">Плотность, $ \text{кг/м}^3 $</th></tr></thead><tbody><tr><td style="padding: 8px;">Алюминий</td><td style="padding: 8px;">2700</td></tr><tr><td style="padding: 8px;">Сталь</td><td style="padding: 8px;">7800</td></tr><tr><td style="padding: 8px;">Медь</td><td style="padding: 8px;">8900</td></tr><tr><td style="padding: 8px;">Вода</td><td style="padding: 8px;">1000</td></tr><tr><td style="padding: 8px;">Дерево (сосна)</td><td style="padding: 8px;">400</td></tr></tbody></table><p><strong>Таблица 6. Удельное электрическое сопротивление (при 20 °C)</strong></p><table border="1" style="border-collapse: collapse; width: 100%;"><thead><tr style="background-color: #f2f2f2;"><th style="padding: 8px; text-align: left;">Вещество</th><th style="padding: 8px; text-align: left;">Удельное сопротивление, $ \text{Ом} \cdot \text{м} $</th></tr></thead><tbody><tr><td style="padding: 8px;">Медь</td><td style="padding: 8px;">$ 1.7 \cdot 10^{-8} $</td></tr><tr><td style="padding: 8px;">Алюминий</td><td style="padding: 8px;">$ 2.8 \cdot 10^{-8} $</td></tr><tr><td style="padding: 8px;">Сталь</td><td style="padding: 8px;">$ 1.2 \cdot 10^{-7} $</td></tr><tr><td style="padding: 8px;">Нихром</td><td style="padding: 8px;">$ 1.1 \cdot 10^{-6} $</td></tr></tbody></table><br><p><strong>Задача 1.</strong></p><p>Стальной шар имеет массу 3.9 кг. Какой объем имеет этот шар? Сравните его массу с массой алюминиевого шара такого же объема.</p><p><strong>Дано:</strong></p><p>$m_{ст} = 3.9 \text{ кг}$<br>$\rho_{ст} = 7800 \text{ кг/м³}$ (из таблицы 5)<br>$\rho_{ал} = 2700 \text{ кг/м³}$ (из таблицы 5)</p><p>Все данные уже представлены в системе СИ.</p><p><strong>Найти:</strong></p><p>$V_{ст}$ - ?<br>$m_{ал}$ - ?</p><p><strong>Решение:</strong></p><p><strong>1.</strong> Плотность, масса и объем тела связаны формулой $ \rho = m/V $. Отсюда можно выразить объем: $ V = m/\rho $.<br>Найдем объем стального шара, используя его массу и плотность стали из таблицы 5:<br>$V_{ст} = m_{ст} / \rho_{ст} = 3.9 \text{ кг} / 7800 \text{ кг/м³} = 0.0005 \text{ м³}$.</p><p><strong>2.</strong> По условию задачи, объем алюминиевого шара равен объему стального: $ V_{ал} = V_{ст} = 0.0005 \text{ м³} $.<br>Найдем массу алюминиевого шара, используя его объем и плотность алюминия из таблицы 5:<br>$m_{ал} = \rho_{ал} \cdot V_{ал} = 2700 \text{ кг/м³} \cdot 0.0005 \text{ м³} = 1.35 \text{ кг}$.</p><p><strong>3.</strong> Сравним массы шаров:<br>$m_{ст} / m_{ал} = 3.9 \text{ кг} / 1.35 \text{ кг} \approx 2.89$.<br>Масса стального шара почти в 2.9 раза больше массы алюминиевого шара того же объема.</p><p><strong>Ответ:</strong> объем стального шара равен $0.0005 \text{ м³}$; масса алюминиевого шара такого же объема составляет $1.35 \text{ кг}$; масса стального шара больше массы алюминиевого шара примерно в 2.89 раза.</p><br><p><strong>Задача 2.</strong></p><p>Определите сопротивление медного провода длиной 100 м и площадью поперечного сечения 0.5 мм². Какой длины должен быть алюминиевый провод с такой же площадью поперечного сечения, чтобы иметь такое же сопротивление?</p><p><strong>Дано:</strong></p><p>$l_м = 100 \text{ м}$<br>$S = 0.5 \text{ мм²}$<br>$\rho_{э, м} = 1.7 \cdot 10^{-8} \text{ Ом·м}$ (из таблицы 6)<br>$\rho_{э, ал} = 2.8 \cdot 10^{-8} \text{ Ом·м}$ (из таблицы 6)<br>$R_{ал} = R_м$</p><p>Переведем площадь сечения в систему СИ (м²):<br>$S = 0.5 \text{ мм²} = 0.5 \cdot (10^{-3} \text{ м})^2 = 0.5 \cdot 10^{-6} \text{ м²}$.</p><p><strong>Найти:</strong></p><p>$R_м$ - ?<br>$l_{ал}$ - ?</p><p><strong>Решение:</strong></p><p><strong>1.</strong> Сопротивление проводника вычисляется по формуле $ R = \rho_э \cdot (l/S) $, где $ \rho_э $ – удельное электрическое сопротивление, $ l $ – длина, $ S $ – площадь поперечного сечения.<br>Найдем сопротивление медного провода, используя данные из условия и таблицы 6:<br>$ R_м = \rho_{э, м} \cdot (l_м / S) = (1.7 \cdot 10^{-8} \text{ Ом·м} \cdot 100 \text{ м}) / (0.5 \cdot 10^{-6} \text{ м²}) = 3.4 \text{ Ом}$.</p><p><strong>2.</strong> По условию, сопротивление алюминиевого провода должно быть таким же: $ R_{ал} = R_м = 3.4 \text{ Ом} $.<br>Из формулы сопротивления $ R_{ал} = \rho_{э, ал} \cdot (l_{ал} / S) $ выразим длину алюминиевого провода $ l_{ал} $:<br>$ l_{ал} = (R_{ал} \cdot S) / \rho_{э, ал} $.<br>Подставим числовые значения:<br>$ l_{ал} = (3.4 \text{ Ом} \cdot 0.5 \cdot 10^{-6} \text{ м²}) / (2.8 \cdot 10^{-8} \text{ Ом·м}) \approx 60.7 \text{ м}$.</p><p><strong>Ответ:</strong> сопротивление медного провода равно $3.4 \text{ Ом}$; чтобы иметь такое же сопротивление, алюминиевый провод с такой же площадью поперечного сечения должен иметь длину примерно $60.7 \text{ м}$.</p>"
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            "text" => "<p>Поскольку в задании не предоставлены таблицы 5 и 6, в качестве примера создадим их и на их основе составим и решим две задачи.</p><p><strong>Таблица 5. Плотность некоторых веществ (при н.у.)</strong></p><table border="1" style="border-collapse: collapse; width: 100%;"><thead><tr style="background-color: #f2f2f2;"><th style="padding: 8px; text-align: left;">Вещество</th><th style="padding: 8px; text-align: left;">Плотность, $ \text{кг/м}^3 $</th></tr></thead><tbody><tr><td style="padding: 8px;">Алюминий</td><td style="padding: 8px;">2700</td></tr><tr><td style="padding: 8px;">Сталь</td><td style="padding: 8px;">7800</td></tr><tr><td style="padding: 8px;">Медь</td><td style="padding: 8px;">8900</td></tr><tr><td style="padding: 8px;">Вода</td><td style="padding: 8px;">1000</td></tr><tr><td style="padding: 8px;">Дерево (сосна)</td><td style="padding: 8px;">400</td></tr></tbody></table><p><strong>Таблица 6. Удельное электрическое сопротивление (при 20 °C)</strong></p><table border="1" style="border-collapse: collapse; width: 100%;"><thead><tr style="background-color: #f2f2f2;"><th style="padding: 8px; text-align: left;">Вещество</th><th style="padding: 8px; text-align: left;">Удельное сопротивление, $ \text{Ом} \cdot \text{м} $</th></tr></thead><tbody><tr><td style="padding: 8px;">Медь</td><td style="padding: 8px;">$ 1.7 \cdot 10^{-8} $</td></tr><tr><td style="padding: 8px;">Алюминий</td><td style="padding: 8px;">$ 2.8 \cdot 10^{-8} $</td></tr><tr><td style="padding: 8px;">Сталь</td><td style="padding: 8px;">$ 1.2 \cdot 10^{-7} $</td></tr><tr><td style="padding: 8px;">Нихром</td><td style="padding: 8px;">$ 1.1 \cdot 10^{-6} $</td></tr></tbody></table><br><p><strong>Задача 1.</strong></p><p>Стальной шар имеет массу 3.9 кг. Какой объем имеет этот шар? Сравните его массу с массой алюминиевого шара такого же объема.</p><p><strong>Дано:</strong></p><p>$m_{ст} = 3.9 \text{ кг}$<br>$\rho_{ст} = 7800 \text{ кг/м³}$ (из таблицы 5)<br>$\rho_{ал} = 2700 \text{ кг/м³}$ (из таблицы 5)</p><p>Все данные уже представлены в системе СИ.</p><p><strong>Найти:</strong></p><p>$V_{ст}$ - ?<br>$m_{ал}$ - ?</p><p><strong>Решение:</strong></p><p><strong>1.</strong> Плотность, масса и объем тела связаны формулой $ \rho = m/V $. Отсюда можно выразить объем: $ V = m/\rho $.<br>Найдем объем стального шара, используя его массу и плотность стали из таблицы 5:<br>$V_{ст} = m_{ст} / \rho_{ст} = 3.9 \text{ кг} / 7800 \text{ кг/м³} = 0.0005 \text{ м³}$.</p><p><strong>2.</strong> По условию задачи, объем алюминиевого шара равен объему стального: $ V_{ал} = V_{ст} = 0.0005 \text{ м³} $.<br>Найдем массу алюминиевого шара, используя его объем и плотность алюминия из таблицы 5:<br>$m_{ал} = \rho_{ал} \cdot V_{ал} = 2700 \text{ кг/м³} \cdot 0.0005 \text{ м³} = 1.35 \text{ кг}$.</p><p><strong>3.</strong> Сравним массы шаров:<br>$m_{ст} / m_{ал} = 3.9 \text{ кг} / 1.35 \text{ кг} \approx 2.89$.<br>Масса стального шара почти в 2.9 раза больше массы алюминиевого шара того же объема.</p><p><strong>Ответ:</strong> объем стального шара равен $0.0005 \text{ м³}$; масса алюминиевого шара такого же объема составляет $1.35 \text{ кг}$; масса стального шара больше массы алюминиевого шара примерно в 2.89 раза.</p><br><p><strong>Задача 2.</strong></p><p>Определите сопротивление медного провода длиной 100 м и площадью поперечного сечения 0.5 мм². Какой длины должен быть алюминиевый провод с такой же площадью поперечного сечения, чтобы иметь такое же сопротивление?</p><p><strong>Дано:</strong></p><p>$l_м = 100 \text{ м}$<br>$S = 0.5 \text{ мм²}$<br>$\rho_{э, м} = 1.7 \cdot 10^{-8} \text{ Ом·м}$ (из таблицы 6)<br>$\rho_{э, ал} = 2.8 \cdot 10^{-8} \text{ Ом·м}$ (из таблицы 6)<br>$R_{ал} = R_м$</p><p>Переведем площадь сечения в систему СИ (м²):<br>$S = 0.5 \text{ мм²} = 0.5 \cdot (10^{-3} \text{ м})^2 = 0.5 \cdot 10^{-6} \text{ м²}$.</p><p><strong>Найти:</strong></p><p>$R_м$ - ?<br>$l_{ал}$ - ?</p><p><strong>Решение:</strong></p><p><strong>1.</strong> Сопротивление проводника вычисляется по формуле $ R = \rho_э \cdot (l/S) $, где $ \rho_э $ – удельное электрическое сопротивление, $ l $ – длина, $ S $ – площадь поперечного сечения.<br>Найдем сопротивление медного провода, используя данные из условия и таблицы 6:<br>$ R_м = \rho_{э, м} \cdot (l_м / S) = (1.7 \cdot 10^{-8} \text{ Ом·м} \cdot 100 \text{ м}) / (0.5 \cdot 10^{-6} \text{ м²}) = 3.4 \text{ Ом}$.</p><p><strong>2.</strong> По условию, сопротивление алюминиевого провода должно быть таким же: $ R_{ал} = R_м = 3.4 \text{ Ом} $.<br>Из формулы сопротивления $ R_{ал} = \rho_{э, ал} \cdot (l_{ал} / S) $ выразим длину алюминиевого провода $ l_{ал} $:<br>$ l_{ал} = (R_{ал} \cdot S) / \rho_{э, ал} $.<br>Подставим числовые значения:<br>$ l_{ал} = (3.4 \text{ Ом} \cdot 0.5 \cdot 10^{-6} \text{ м²}) / (2.8 \cdot 10^{-8} \text{ Ом·м}) \approx 60.7 \text{ м}$.</p><p><strong>Ответ:</strong> сопротивление медного провода равно $3.4 \text{ Ом}$; чтобы иметь такое же сопротивление, алюминиевый провод с такой же площадью поперечного сечения должен иметь длину примерно $60.7 \text{ м}$.</p>"
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№2 (с. 78)
Условие. №2 (с. 78)
скриншот условия
Физика, 8 класс Учебник, автор: Пёрышкин И М, издательство Просвещение, Москва, 2023, белого цвета, страница 78, номер 2, Условие

2. Придумайте несколько задач, используя данные таблиц 5 и 6. Обменяйтесь с товарищем условиями задач и решите их.

Придумать несколько задач, используя данные таблиц 5 и 6
Придумать несколько задач, используя данные таблиц 5 и 6
Решение 1. №2 (с. 78)
Физика, 8 класс Учебник, автор: Пёрышкин И М, издательство Просвещение, Москва, 2023, белого цвета, страница 78, номер 2, Решение 1
Решение 3. №2 (с. 78)
Физика, 8 класс Учебник, автор: Пёрышкин И М, издательство Просвещение, Москва, 2023, белого цвета, страница 78, номер 2, Решение 3
Решение 4. №2 (с. 78)

Поскольку в задании не предоставлены таблицы 5 и 6, в качестве примера создадим их и на их основе составим и решим две задачи.

Таблица 5. Плотность некоторых веществ (при н.у.)

ВеществоПлотность, $ \text{кг/м}^3 $
Алюминий2700
Сталь7800
Медь8900
Вода1000
Дерево (сосна)400

Таблица 6. Удельное электрическое сопротивление (при 20 °C)

ВеществоУдельное сопротивление, $ \text{Ом} \cdot \text{м} $
Медь$ 1.7 \cdot 10^{-8} $
Алюминий$ 2.8 \cdot 10^{-8} $
Сталь$ 1.2 \cdot 10^{-7} $
Нихром$ 1.1 \cdot 10^{-6} $

Задача 1.

Стальной шар имеет массу 3.9 кг. Какой объем имеет этот шар? Сравните его массу с массой алюминиевого шара такого же объема.

Дано:

$m_{ст} = 3.9 \text{ кг}$
$\rho_{ст} = 7800 \text{ кг/м³}$ (из таблицы 5)
$\rho_{ал} = 2700 \text{ кг/м³}$ (из таблицы 5)

Все данные уже представлены в системе СИ.

Найти:

$V_{ст}$ - ?
$m_{ал}$ - ?

Решение:

1. Плотность, масса и объем тела связаны формулой $ \rho = m/V $. Отсюда можно выразить объем: $ V = m/\rho $.
Найдем объем стального шара, используя его массу и плотность стали из таблицы 5:
$V_{ст} = m_{ст} / \rho_{ст} = 3.9 \text{ кг} / 7800 \text{ кг/м³} = 0.0005 \text{ м³}$.

2. По условию задачи, объем алюминиевого шара равен объему стального: $ V_{ал} = V_{ст} = 0.0005 \text{ м³} $.
Найдем массу алюминиевого шара, используя его объем и плотность алюминия из таблицы 5:
$m_{ал} = \rho_{ал} \cdot V_{ал} = 2700 \text{ кг/м³} \cdot 0.0005 \text{ м³} = 1.35 \text{ кг}$.

3. Сравним массы шаров:
$m_{ст} / m_{ал} = 3.9 \text{ кг} / 1.35 \text{ кг} \approx 2.89$.
Масса стального шара почти в 2.9 раза больше массы алюминиевого шара того же объема.

Ответ: объем стального шара равен $0.0005 \text{ м³}$; масса алюминиевого шара такого же объема составляет $1.35 \text{ кг}$; масса стального шара больше массы алюминиевого шара примерно в 2.89 раза.


Задача 2.

Определите сопротивление медного провода длиной 100 м и площадью поперечного сечения 0.5 мм². Какой длины должен быть алюминиевый провод с такой же площадью поперечного сечения, чтобы иметь такое же сопротивление?

Дано:

$l_м = 100 \text{ м}$
$S = 0.5 \text{ мм²}$
$\rho_{э, м} = 1.7 \cdot 10^{-8} \text{ Ом·м}$ (из таблицы 6)
$\rho_{э, ал} = 2.8 \cdot 10^{-8} \text{ Ом·м}$ (из таблицы 6)
$R_{ал} = R_м$

Переведем площадь сечения в систему СИ (м²):
$S = 0.5 \text{ мм²} = 0.5 \cdot (10^{-3} \text{ м})^2 = 0.5 \cdot 10^{-6} \text{ м²}$.

Найти:

$R_м$ - ?
$l_{ал}$ - ?

Решение:

1. Сопротивление проводника вычисляется по формуле $ R = \rho_э \cdot (l/S) $, где $ \rho_э $ – удельное электрическое сопротивление, $ l $ – длина, $ S $ – площадь поперечного сечения.
Найдем сопротивление медного провода, используя данные из условия и таблицы 6:
$ R_м = \rho_{э, м} \cdot (l_м / S) = (1.7 \cdot 10^{-8} \text{ Ом·м} \cdot 100 \text{ м}) / (0.5 \cdot 10^{-6} \text{ м²}) = 3.4 \text{ Ом}$.

2. По условию, сопротивление алюминиевого провода должно быть таким же: $ R_{ал} = R_м = 3.4 \text{ Ом} $.
Из формулы сопротивления $ R_{ал} = \rho_{э, ал} \cdot (l_{ал} / S) $ выразим длину алюминиевого провода $ l_{ал} $:
$ l_{ал} = (R_{ал} \cdot S) / \rho_{э, ал} $.
Подставим числовые значения:
$ l_{ал} = (3.4 \text{ Ом} \cdot 0.5 \cdot 10^{-6} \text{ м²}) / (2.8 \cdot 10^{-8} \text{ Ом·м}) \approx 60.7 \text{ м}$.

Ответ: сопротивление медного провода равно $3.4 \text{ Ом}$; чтобы иметь такое же сопротивление, алюминиевый провод с такой же площадью поперечного сечения должен иметь длину примерно $60.7 \text{ м}$.

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