Номер 8.2, страница 57 - гдз по физике 10-11 класс задачник Гельфгат, Генденштейн

Физика, 10-11 класс Задачник, авторы: Гельфгат Илья Маркович, Генденштейн Лев Элевич, Кирик Леонид Анатольевич, издательство Илекса, Москва, 2008, красного цвета

Авторы: Гельфгат И. М., Генденштейн Л. Э., Кирик Л. А.

Тип: Задачник

Издательство: Илекса

Год издания: 2008 - 2026

Уровень обучения: профильный

Цвет обложки: красный лупа, парень едет на велосипеде

ISBN: 978-5-89237-252-7

Механика. Динамика. 8. Применение законов динамики. Упражнения - номер 8.2, страница 57.

App\Models\Task {#1030 // resources/views/models/task/default.blade.php
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  #table: "tasks"
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        0 => App\Models\Term {#1036
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              #items: array:1 [
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                      #items: array:2 [
                        0 => App\Models\Term {#1052
                          #connection: "mysql"
                          #table: "terms"
                          #primaryKey: "id"
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                            "created_at" => "2026-04-10 13:58:26"
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                        1 => App\Models\Term {#1053
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                              "field_prepositional_case" => "задачнике"
                            ]
                            "field_plural_form" => null
                            "field_short_name" => null
                            "field_short_name_foreign" => null
                            "field_translit" => "zadachnik"
                          ]
                          #changes: []
                          #casts: []
                          #classCastCache: []
                          #attributeCastCache: []
                          #dateFormat: null
                          #appends: []
                          #dispatchesEvents: []
                          #observables: []
                          #relations: []
                          #touches: []
                          +timestamps: true
                          +usesUniqueIds: false
                          #hidden: []
                          #visible: []
                          #fillable: []
                          #guarded: array:1 [
                            0 => "*"
                          ]
                        }
                      ]
                      #escapeWhenCastingToString: false
                    }
                    "field_country" => Illuminate\Database\Eloquent\Collection {#1063
                      #items: array:1 [
                        0 => App\Models\Term {#1064
                          #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 [
                              "field_accusative_case" => null
                              "field_creative_case" => null
                              "field_dative_case" => null
                              "field_genitive_case" => null
                              "field_nominative_case" => null
                              "field_prepositional_case" => null
                            ]
                            "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 [
                              "field_accusative_case" => null
                              "field_creative_case" => null
                              "field_dative_case" => null
                              "field_genitive_case" => null
                              "field_nominative_case" => null
                              "field_prepositional_case" => null
                            ]
                            "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 {#1065
                      #items: array:1 [
                        0 => App\Models\Term {#1066
                          #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 [
                              "field_accusative_case" => null
                              "field_creative_case" => null
                              "field_dative_case" => null
                              "field_genitive_case" => null
                              "field_nominative_case" => null
                              "field_prepositional_case" => null
                            ]
                            "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 [
                              "field_accusative_case" => null
                              "field_creative_case" => null
                              "field_dative_case" => null
                              "field_genitive_case" => null
                              "field_nominative_case" => null
                              "field_prepositional_case" => null
                            ]
                            "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 {#1067
                      #items: []
                      #escapeWhenCastingToString: false
                    }
                    "field_umk" => Illuminate\Database\Eloquent\Collection {#1068
                      #items: []
                      #escapeWhenCastingToString: false
                    }
                    "field_level_of_education" => Illuminate\Database\Eloquent\Collection {#1069
                      #items: array:1 [
                        0 => App\Models\Term {#1070
                          #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" => 40
                            "created_at" => "2026-04-10 13:58:26"
                            "updated_at" => null
                            "name" => "профильный"
                            "field_cases" => array:6 [
                              "field_accusative_case" => "профильный"
                              "field_creative_case" => "профильным"
                              "field_dative_case" => "профильному"
                              "field_genitive_case" => "профильного"
                              "field_nominative_case" => "профильный"
                              "field_prepositional_case" => "профильном"
                            ]
                            "field_translit" => "profilnyy"
                          ]
                          #original: array:6 [
                            "id" => 40
                            "created_at" => "2026-04-10 13:58:26"
                            "updated_at" => null
                            "name" => "профильный"
                            "field_cases" => array:6 [
                              "field_accusative_case" => "профильный"
                              "field_creative_case" => "профильным"
                              "field_dative_case" => "профильному"
                              "field_genitive_case" => "профильного"
                              "field_nominative_case" => "профильный"
                              "field_prepositional_case" => "профильном"
                            ]
                            "field_translit" => "profilnyy"
                          ]
                          #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_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: []
                      #escapeWhenCastingToString: false
                    }
                    "field_under_the_edition_degree" => null
                    "field_cover_description" => "лупа, парень едет на велосипеде"
                    "field_publication_year" => "2008"
                    "field_publication_year_until" => null
                    "field_part" => ""
                    "field_part_writing" => ""
                    "field_second_foreign_language" => null
                    "field_for_whom" => "Учебное издание"
                    "field_allowed" => null
                    "field_reserve_field" => null
                    "field_link_to_source" => null
                    "field_tasks_count" => "459"
                    "field_priority" => null
                    "field_default_folder" => "/fizika_10/gelfgat-z/"
                    "field_isbn" => "978-5-89237-252-7"
                    "field_cover" => array:1 [
                      0 => "/media/fizika_10/gelfgat-z/covers/cover1.webp?ts=1756049816"
                    ]
                    "field_cover_alts" => array:1 [
                      0 => ""
                    ]
                    "field_covers" => array:1 [
                      0 => array:4 [
                        "path" => "/media/fizika_10/gelfgat-z/covers/cover1.webp?ts=1756049816"
                        "alt" => ""
                        "width" => "1566"
                        "height" => "2412"
                      ]
                    ]
                    "field_popular_book" => "0"
                    "field_recommended_books" => Illuminate\Database\Eloquent\Collection {#1074
                      #items: []
                      #escapeWhenCastingToString: false
                    }
                    "field_new_book" => Illuminate\Database\Eloquent\Collection {#1075
                      #items: []
                      #escapeWhenCastingToString: false
                    }
                    "field_old_book" => Illuminate\Database\Eloquent\Collection {#1076
                      #items: []
                      #escapeWhenCastingToString: false
                    }
                    "field_url" => "/10-klass/fizika/gelfgat-zadachnik"
                    "field_cover_color" => Illuminate\Database\Eloquent\Collection {#1077
                      #items: array:1 [
                        0 => App\Models\Term {#1078
                          #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" => 46
                            "created_at" => "2026-04-10 13:58:26"
                            "updated_at" => null
                            "name" => "красный"
                            "field_cases" => array:6 [
                              "field_accusative_case" => "красный"
                              "field_creative_case" => "красным"
                              "field_dative_case" => "красному"
                              "field_genitive_case" => "красного"
                              "field_nominative_case" => "красный"
                              "field_prepositional_case" => "красном"
                            ]
                            "field_translit" => "krasnyy"
                          ]
                          #original: array:6 [
                            "id" => 46
                            "created_at" => "2026-04-10 13:58:26"
                            "updated_at" => null
                            "name" => "красный"
                            "field_cases" => array:6 [
                              "field_accusative_case" => "красный"
                              "field_creative_case" => "красным"
                              "field_dative_case" => "красному"
                              "field_genitive_case" => "красного"
                              "field_nominative_case" => "красный"
                              "field_prepositional_case" => "красном"
                            ]
                            "field_translit" => "krasnyy"
                          ]
                          #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" => 381
                      "subject" => 556
                      "class_subject" => 494
                    ]
                  ]
                  #original: array:50 [
                    "id" => 5400
                    "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 {#1050}
                    "field_class" => Illuminate\Database\Eloquent\Collection {#1051}
                    "field_publisher" => Illuminate\Database\Eloquent\Collection {#1054}
                    "field_author" => Illuminate\Database\Eloquent\Collection {#1056}
                    "field_author_foreign" => Illuminate\Database\Eloquent\Collection {#1060}
                    "field_book_type" => Illuminate\Database\Eloquent\Collection {#1061}
                    "field_country" => Illuminate\Database\Eloquent\Collection {#1063}
                    "field_city" => Illuminate\Database\Eloquent\Collection {#1065}
                    "field_series" => Illuminate\Database\Eloquent\Collection {#1067}
                    "field_umk" => Illuminate\Database\Eloquent\Collection {#1068}
                    "field_level_of_education" => Illuminate\Database\Eloquent\Collection {#1069}
                    "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" => "лупа, парень едет на велосипеде"
                    "field_publication_year" => "2008"
                    "field_publication_year_until" => null
                    "field_part" => ""
                    "field_part_writing" => ""
                    "field_second_foreign_language" => null
                    "field_for_whom" => "Учебное издание"
                    "field_allowed" => null
                    "field_reserve_field" => null
                    "field_link_to_source" => null
                    "field_tasks_count" => "459"
                    "field_priority" => null
                    "field_default_folder" => "/fizika_10/gelfgat-z/"
                    "field_isbn" => "978-5-89237-252-7"
                    "field_cover" => array:1 [
                      0 => "/media/fizika_10/gelfgat-z/covers/cover1.webp?ts=1756049816"
                    ]
                    "field_cover_alts" => array:1 [
                      0 => ""
                    ]
                    "field_covers" => array:1 [
                      0 => array:4 [
                        "path" => "/media/fizika_10/gelfgat-z/covers/cover1.webp?ts=1756049816"
                        "alt" => ""
                        "width" => "1566"
                        "height" => "2412"
                      ]
                    ]
                    "field_popular_book" => "0"
                    "field_recommended_books" => Illuminate\Database\Eloquent\Collection {#1074}
                    "field_new_book" => Illuminate\Database\Eloquent\Collection {#1075}
                    "field_old_book" => Illuminate\Database\Eloquent\Collection {#1076}
                    "field_url" => "/10-klass/fizika/gelfgat-zadachnik"
                    "field_cover_color" => Illuminate\Database\Eloquent\Collection {#1077}
                    "field_metatags_title" => null
                    "field_metatags_description" => null
                    "field_h1" => null
                    "field_description_top" => null
                    "field_description_bottom" => null
                    "breadcrumbs" => array:3 [
                      "class" => 381
                      "subject" => 556
                      "class_subject" => 494
                    ]
                  ]
                  #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 {#1079
              #items: []
              #escapeWhenCastingToString: false
            }
          ]
          #original: array:24 [
            "id" => 1319266
            "created_at" => "2026-04-10 13:58:26"
            "updated_at" => null
            "field_display_title" => "Механика"
            "field_branch_order" => null
            "field_url" => null
            "field_branch_type" => Illuminate\Database\Eloquent\Collection {#1047}
            "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 {#1081}
            "branch_parent" => Illuminate\Database\Eloquent\Collection {#1079}
          ]
          #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 {#1111
      #items: array:4 [
        0 => App\Models\Branch {#1121
          #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" => 1319266
            "created_at" => "2026-04-10 13:58:26"
            "updated_at" => null
            "field_display_title" => "Механика"
            "field_branch_order" => null
            "field_url" => null
            "field_branch_type" => Illuminate\Database\Eloquent\Collection {#1122
              #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 {#1123
              #items: array:1 [
                0 => App\Models\Book {#1048}
              ]
              #escapeWhenCastingToString: false
            }
            "branch_parent" => Illuminate\Database\Eloquent\Collection {#1124
              #items: []
              #escapeWhenCastingToString: false
            }
          ]
          #original: array:24 [
            "id" => 1319266
            "created_at" => "2026-04-10 13:58:26"
            "updated_at" => null
            "field_display_title" => "Механика"
            "field_branch_order" => null
            "field_url" => null
            "field_branch_type" => Illuminate\Database\Eloquent\Collection {#1122}
            "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 {#1123}
            "branch_parent" => Illuminate\Database\Eloquent\Collection {#1124}
          ]
          #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 {#1125
          #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" => 1319280
            "created_at" => "2026-04-10 13:58:26"
            "updated_at" => null
            "field_display_title" => "Динамика"
            "field_branch_order" => null
            "field_url" => null
            "field_branch_type" => Illuminate\Database\Eloquent\Collection {#1126
              #items: []
              #escapeWhenCastingToString: false
            }
            "field_page_start" => "40"
            "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 {#1127
              #items: array:1 [
                0 => App\Models\Book {#1048}
              ]
              #escapeWhenCastingToString: false
            }
            "branch_parent" => Illuminate\Database\Eloquent\Collection {#1128
              #items: array:1 [
                0 => App\Models\Branch {#1045}
              ]
              #escapeWhenCastingToString: false
            }
          ]
          #original: array:24 [
            "id" => 1319280
            "created_at" => "2026-04-10 13:58:26"
            "updated_at" => null
            "field_display_title" => "Динамика"
            "field_branch_order" => null
            "field_url" => null
            "field_branch_type" => Illuminate\Database\Eloquent\Collection {#1126}
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        }
        2 => App\Models\Branch {#1129
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                0 => App\Models\Branch {#1139
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        3 => App\Models\Branch {#1133
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                0 => App\Models\Branch {#1148
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    "content" => Illuminate\Database\Eloquent\Collection {#1038
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            "edition" => Illuminate\Database\Eloquent\Collection {#1092
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                    "field_publisher" => Illuminate\Database\Eloquent\Collection {#1098
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            "task" => array:2 [
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            "text" => "<p><strong>8.2.</strong> К концам шнура, перекинутого через блок, подвешены грузы с массами $m_1 = 100 \text{ г}$ и $m_2 = 150 \text{ г}$. Найдите ускорение грузов, силу натяжения шнура $\text{T}$ и показание $\text{F}$ динамометра, на котором висит блок.</p><p>☑ 2 м/с$^2$; 1,2 Н; 2,4 Н.</p><p><strong>Решение.</strong> Благодаря нерастяжимости шнура перемещения обоих грузов одинаковы по величине; значит, одинаковы по величине и их ускорения: $a_1 = a_2 = a$. Пренебрегая массами шнура и блока, а также трением в блоке, можно считать силу $\text{T}$ натяжения шнура всюду одинаковой. На рисунке а показаны действующие на грузы силы. Запишем уравнения второго закона Ньютона для каждого из грузов в проекции на ось $\text{y}$:</p><p>$\begin{cases} m_1 a = -m_1 g + T \\ -m_2 a = -m_2 g + T \end{cases}$</p><p>Отсюда $a = \frac{m_2 - m_1}{m_2 + m_1} g = 2,0 \text{ (м/с}^2\text{)}$, $T = \frac{2m_1 m_2 g}{m_1 + m_2} = 1,2 \text{ (Н)}$.</p><p>Для нахождения силы $\text{F}$ упругости пружины динамометра надо рассмотреть силы, действующие на блок (см. рис. б).</p><p>Из условия равновесия блока получаем, что $F = 2T = 2,4 \text{ (Н)}$. На примере данной задачи покажем два эффективных метода проверки полученного результата.</p><p><strong>Первый из них — проверка на симметрию.</strong> Очевидно, если поменять грузы местами, натяжение шнура и величина ускорения грузов не должны измениться. Полученные для $\text{a}$ и $\text{T}$ выражения этому требованию удовлетворяют (при замене $m_1 \leftrightarrow m_2$, значение $\text{T}$ не изменяется, а ускорение меняет только знак).</p><p><strong>Второй метод — проверка на частные и предельные случаи.</strong> Например, при $m_1 = m_2 = m$ ускорение должно быть равно нулю, а $T = mg$. При $m_1 \rightarrow 0$ должно быть $a \rightarrow g$, $T \rightarrow 0$ (груз 2 свободно падает и поэтому находится в состоянии невесомости). Полученные формулы удовлетворяют и этим требованиям. Обратим внимание на то, что вес обоих грузов одинаков, как бы сильно ни отличались их массы: ведь оба груза действуют на шнур с одинаковыми силами. Дело в том, что вес меньшего груза увеличивается (ускорение этого груза направлено вверх), а вес большего груза уменьшается (ускорение этого груза направлено вниз).</p>"
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            "text" => "<p><strong>8.2.</strong> К концам шнура, перекинутого через блок, подвешены грузы с массами $m_1 = 100 \text{ г}$ и $m_2 = 150 \text{ г}$. Найдите ускорение грузов, силу натяжения шнура $\text{T}$ и показание $\text{F}$ динамометра, на котором висит блок.</p><p>☑ 2 м/с$^2$; 1,2 Н; 2,4 Н.</p><p><strong>Решение.</strong> Благодаря нерастяжимости шнура перемещения обоих грузов одинаковы по величине; значит, одинаковы по величине и их ускорения: $a_1 = a_2 = a$. Пренебрегая массами шнура и блока, а также трением в блоке, можно считать силу $\text{T}$ натяжения шнура всюду одинаковой. На рисунке а показаны действующие на грузы силы. Запишем уравнения второго закона Ньютона для каждого из грузов в проекции на ось $\text{y}$:</p><p>$\begin{cases} m_1 a = -m_1 g + T \\ -m_2 a = -m_2 g + T \end{cases}$</p><p>Отсюда $a = \frac{m_2 - m_1}{m_2 + m_1} g = 2,0 \text{ (м/с}^2\text{)}$, $T = \frac{2m_1 m_2 g}{m_1 + m_2} = 1,2 \text{ (Н)}$.</p><p>Для нахождения силы $\text{F}$ упругости пружины динамометра надо рассмотреть силы, действующие на блок (см. рис. б).</p><p>Из условия равновесия блока получаем, что $F = 2T = 2,4 \text{ (Н)}$. На примере данной задачи покажем два эффективных метода проверки полученного результата.</p><p><strong>Первый из них — проверка на симметрию.</strong> Очевидно, если поменять грузы местами, натяжение шнура и величина ускорения грузов не должны измениться. Полученные для $\text{a}$ и $\text{T}$ выражения этому требованию удовлетворяют (при замене $m_1 \leftrightarrow m_2$, значение $\text{T}$ не изменяется, а ускорение меняет только знак).</p><p><strong>Второй метод — проверка на частные и предельные случаи.</strong> Например, при $m_1 = m_2 = m$ ускорение должно быть равно нулю, а $T = mg$. При $m_1 \rightarrow 0$ должно быть $a \rightarrow g$, $T \rightarrow 0$ (груз 2 свободно падает и поэтому находится в состоянии невесомости). Полученные формулы удовлетворяют и этим требованиям. Обратим внимание на то, что вес обоих грузов одинаков, как бы сильно ни отличались их массы: ведь оба груза действуют на шнур с одинаковыми силами. Дело в том, что вес меньшего груза увеличивается (ускорение этого груза направлено вверх), а вес большего груза уменьшается (ускорение этого груза направлено вниз).</p>"
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            "text" => "<p><strong>Дано:</strong></p><p>$m_1 = 100$ г</p><p>$m_2 = 150$ г</p><p>В системе СИ:</p><p>$m_1 = 0.1$ кг</p><p>$m_2 = 0.15$ кг</p><p>Ускорение свободного падения $g \approx 10 \, \text{м/с}^2$.</p><p><strong>Найти:</strong></p><p>$a$ — ускорение грузов;</p><p>$T$ — сила натяжения шнура;</p><p>$F$ — показание динамометра.</p><p><strong>Решение:</strong></p><p>Данная система представляет собой машину Атвуда. Будем считать шнур нерастяжимым и невесомым, а блок — идеальным (невесомым и без трения).</p><p><strong>1.</strong> Ускорение грузов (a)</p><p>Поскольку $m_2 &gt; m_1$, груз $m_2$ будет опускаться, а груз $m_1$ — подниматься. Из-за нерастяжимости шнура ускорения обоих грузов будут одинаковы по модулю. Обозначим модуль ускорения как $a$.</p><p>Запишем второй закон Ньютона для каждого груза в проекции на вертикальную ось $y$, направленную вверх:</p><p>Для груза $m_1$: $m_1a = T - m_1g$</p><p>Для груза $m_2$: $-m_2a = T - m_2g$ (ускорение направлено вниз, поэтому проекция отрицательна)</p><p>Получаем систему уравнений:</p><p>$$ \begin{cases} T = m_1a + m_1g \\ T = m_2g - m_2a \end{cases} $$</p><p>Приравняем правые части уравнений, чтобы найти ускорение $a$:</p><p>$m_1a + m_1g = m_2g - m_2a$</p><p>$a(m_1 + m_2) = g(m_2 - m_1)$</p><p>$a = \frac{m_2 - m_1}{m_1 + m_2}g$</p><p>Подставим числовые значения:</p><p>$a = \frac{0.15 \, \text{кг} - 0.1 \, \text{кг}}{0.15 \, \text{кг} + 0.1 \, \text{кг}} \cdot 10 \, \frac{\text{м}}{\text{с}^2} = \frac{0.05}{0.25} \cdot 10 \, \frac{\text{м}}{\text{с}^2} = 0.2 \cdot 10 \, \frac{\text{м}}{\text{с}^2} = 2 \, \frac{\text{м}}{\text{с}^2}$</p><p><strong>Ответ:</strong> Ускорение грузов равно $2 \, \text{м/с}^2$.</p><p><strong>2.</strong> Сила натяжения шнура (T)</p><p>Для нахождения силы натяжения шнура $T$ подставим найденное значение ускорения $a$ в любое из уравнений системы. Воспользуемся первым:</p><p>$T = m_1(a + g)$</p><p>Подставим числовые значения:</p><p>$T = 0.1 \, \text{кг} \cdot (2 \, \frac{\text{м}}{\text{с}^2} + 10 \, \frac{\text{м}}{\text{с}^2}) = 0.1 \, \text{кг} \cdot 12 \, \frac{\text{м}}{\text{с}^2} = 1.2 \, \text{Н}$</p><p><strong>Ответ:</strong> Сила натяжения шнура равна $1.2 \, \text{Н}$.</p><p><strong>3.</strong> Показание динамометра (F)</p><p>Динамометр измеряет силу, с которой система "блок-грузы" действует на него. Эта сила равна по модулю силе упругости $F$, которая уравновешивает силы, действующие на блок со стороны шнура. На невесомый блок действуют две силы натяжения $T$, направленные вертикально вниз (по одной от каждого конца шнура).</p><p>Из условия равновесия блока следует, что показание динамометра $F$ равно сумме сил натяжения:</p><p>$F = T + T = 2T$</p><p>Подставим найденное значение $T$:</p><p>$F = 2 \cdot 1.2 \, \text{Н} = 2.4 \, \text{Н}$</p><p><strong>Ответ:</strong> Показание динамометра равно $2.4 \, \text{Н}$.</p>"
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            "text" => "<p><strong>Дано:</strong></p><p>$m_1 = 100$ г</p><p>$m_2 = 150$ г</p><p>В системе СИ:</p><p>$m_1 = 0.1$ кг</p><p>$m_2 = 0.15$ кг</p><p>Ускорение свободного падения $g \approx 10 \, \text{м/с}^2$.</p><p><strong>Найти:</strong></p><p>$a$ — ускорение грузов;</p><p>$T$ — сила натяжения шнура;</p><p>$F$ — показание динамометра.</p><p><strong>Решение:</strong></p><p>Данная система представляет собой машину Атвуда. Будем считать шнур нерастяжимым и невесомым, а блок — идеальным (невесомым и без трения).</p><p><strong>1.</strong> Ускорение грузов (a)</p><p>Поскольку $m_2 &gt; m_1$, груз $m_2$ будет опускаться, а груз $m_1$ — подниматься. Из-за нерастяжимости шнура ускорения обоих грузов будут одинаковы по модулю. Обозначим модуль ускорения как $a$.</p><p>Запишем второй закон Ньютона для каждого груза в проекции на вертикальную ось $y$, направленную вверх:</p><p>Для груза $m_1$: $m_1a = T - m_1g$</p><p>Для груза $m_2$: $-m_2a = T - m_2g$ (ускорение направлено вниз, поэтому проекция отрицательна)</p><p>Получаем систему уравнений:</p><p>$$ \begin{cases} T = m_1a + m_1g \\ T = m_2g - m_2a \end{cases} $$</p><p>Приравняем правые части уравнений, чтобы найти ускорение $a$:</p><p>$m_1a + m_1g = m_2g - m_2a$</p><p>$a(m_1 + m_2) = g(m_2 - m_1)$</p><p>$a = \frac{m_2 - m_1}{m_1 + m_2}g$</p><p>Подставим числовые значения:</p><p>$a = \frac{0.15 \, \text{кг} - 0.1 \, \text{кг}}{0.15 \, \text{кг} + 0.1 \, \text{кг}} \cdot 10 \, \frac{\text{м}}{\text{с}^2} = \frac{0.05}{0.25} \cdot 10 \, \frac{\text{м}}{\text{с}^2} = 0.2 \cdot 10 \, \frac{\text{м}}{\text{с}^2} = 2 \, \frac{\text{м}}{\text{с}^2}$</p><p><strong>Ответ:</strong> Ускорение грузов равно $2 \, \text{м/с}^2$.</p><p><strong>2.</strong> Сила натяжения шнура (T)</p><p>Для нахождения силы натяжения шнура $T$ подставим найденное значение ускорения $a$ в любое из уравнений системы. Воспользуемся первым:</p><p>$T = m_1(a + g)$</p><p>Подставим числовые значения:</p><p>$T = 0.1 \, \text{кг} \cdot (2 \, \frac{\text{м}}{\text{с}^2} + 10 \, \frac{\text{м}}{\text{с}^2}) = 0.1 \, \text{кг} \cdot 12 \, \frac{\text{м}}{\text{с}^2} = 1.2 \, \text{Н}$</p><p><strong>Ответ:</strong> Сила натяжения шнура равна $1.2 \, \text{Н}$.</p><p><strong>3.</strong> Показание динамометра (F)</p><p>Динамометр измеряет силу, с которой система "блок-грузы" действует на него. Эта сила равна по модулю силе упругости $F$, которая уравновешивает силы, действующие на блок со стороны шнура. На невесомый блок действуют две силы натяжения $T$, направленные вертикально вниз (по одной от каждого конца шнура).</p><p>Из условия равновесия блока следует, что показание динамометра $F$ равно сумме сил натяжения:</p><p>$F = T + T = 2T$</p><p>Подставим найденное значение $T$:</p><p>$F = 2 \cdot 1.2 \, \text{Н} = 2.4 \, \text{Н}$</p><p><strong>Ответ:</strong> Показание динамометра равно $2.4 \, \text{Н}$.</p>"
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                        "path" => "/media/fizika_10/gelfgat-z/0-1/57-1.webp?ts=1756642307"
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                  #original: array:6 [
                    "id" => 1519563
                    "created_at" => "2026-04-10 13:58:26"
                    "updated_at" => null
                    "edition" => Illuminate\Database\Eloquent\Collection {#1116}
                    "book_page" => array:2 [
                      "refs" => "1341018"
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                    "img" => array:1 [
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                        "alt" => null
                        "width" => "1588"
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            "next" => array:2 [
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              "refs" => "1341017"
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            "tasks" => Illuminate\Database\Eloquent\Collection {#1220
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                0 => App\Models\Task {#1228
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                  #table: "tasks"
                  #primaryKey: "id"
                  #keyType: "int"
                  +incrementing: true
                  #with: []
                  #withCount: []
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                  #escapeWhenCastingToString: false
                  #attributes: array:24 [
                    "id" => 1319468
                    "created_at" => "2026-04-10 13:58:26"
                    "updated_at" => null
                    "field_page_start" => "57"
                    "field_page_end" => null
                    "field_url" => "/10-klass/fizika/gelfgat-zadachnik/08-1"
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                    "field_task_type" => Illuminate\Database\Eloquent\Collection {#1229
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                        0 => App\Models\Branch {#1121}
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                    "parent_branches" => Illuminate\Database\Eloquent\Collection {#1232
                      #items: array:4 [
                        0 => App\Models\Branch {#1121}
                        1 => App\Models\Branch {#1125}
                        2 => App\Models\Branch {#1129}
                        3 => App\Models\Branch {#1133}
                      ]
                      #escapeWhenCastingToString: false
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                    "content" => Illuminate\Database\Eloquent\Collection {#1234
                      #items: array:2 [
                        0 => App\Models\Element {#1243
                          #connection: "mysql"
                          #table: "elements"
                          #primaryKey: "id"
                          #keyType: "int"
                          +incrementing: true
                          #with: []
                          #withCount: []
                          +preventsLazyLoading: false
                          #perPage: 15
                          +exists: true
                          +wasRecentlyCreated: false
                          #escapeWhenCastingToString: false
                          #attributes: array:7 [
                            "id" => 1493723
                            "created_at" => "2026-04-10 13:58:26"
                            "updated_at" => null
                            "edition" => Illuminate\Database\Eloquent\Collection {#1244
                              #items: array:1 [
                                0 => App\Models\Edition {#1101}
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                              #escapeWhenCastingToString: false
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                            "task" => array:2 [
                              "refs" => "1319468"
                              "type" => "task"
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                            "text" => "<p><strong>8.1.</strong> На тележке, движущейся горизонтально с ускорением $\text{a}$, установлен штатив, на котором подвешен шарик на нити. Найдите угол $\alpha$ отклонения нити от вертикали и силу $\text{T}$ натяжения нити.</p><p>$\alpha = \text{arctg}(a/g); T = m\sqrt{g^2 + a^2}$</p><p><strong>Решение.</strong> На шарик действуют сила тяжести $m\vec{g}$ и сила $\vec{T}$ натяжения нити (см. рисунок). Их равнодействующая $\vec{F}$ сообщает шарику ускорение $\vec{a}$, т. е. $\vec{F} = m\vec{a}$.</p><p><strong>Следовательно,</strong> $tg \alpha = a/g$.</p><p><strong>Воспользовавшись теоремой Пифагора,</strong> находим, что $T = m\sqrt{g^2 + a^2}$.</p>"
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                                "alt" => null
                                "width" => "1420"
                                "height" => 865
                                "path" => "/media/fizika_10/gelfgat-z/0-08/1-1.webp?ts=1756251021"
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                          #original: array:7 [
                            "id" => 1493723
                            "created_at" => "2026-04-10 13:58:26"
                            "updated_at" => null
                            "edition" => Illuminate\Database\Eloquent\Collection {#1244}
                            "task" => array:2 [
                              "refs" => "1319468"
                              "type" => "task"
                            ]
                            "text" => "<p><strong>8.1.</strong> На тележке, движущейся горизонтально с ускорением $\text{a}$, установлен штатив, на котором подвешен шарик на нити. Найдите угол $\alpha$ отклонения нити от вертикали и силу $\text{T}$ натяжения нити.</p><p>$\alpha = \text{arctg}(a/g); T = m\sqrt{g^2 + a^2}$</p><p><strong>Решение.</strong> На шарик действуют сила тяжести $m\vec{g}$ и сила $\vec{T}$ натяжения нити (см. рисунок). Их равнодействующая $\vec{F}$ сообщает шарику ускорение $\vec{a}$, т. е. $\vec{F} = m\vec{a}$.</p><p><strong>Следовательно,</strong> $tg \alpha = a/g$.</p><p><strong>Воспользовавшись теоремой Пифагора,</strong> находим, что $T = m\sqrt{g^2 + a^2}$.</p>"
                            "img" => array:1 [
                              0 => array:5 [
                                "name" => "1-1.jpg"
                                "alt" => null
                                "width" => "1420"
                                "height" => 865
                                "path" => "/media/fizika_10/gelfgat-z/0-08/1-1.webp?ts=1756251021"
                              ]
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                          ]
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                          #dateFormat: null
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                          +usesUniqueIds: false
                          #hidden: []
                          #visible: []
                          #fillable: []
                          #guarded: array:1 [
                            0 => "*"
                          ]
                        }
                        1 => App\Models\Element {#1245
                          #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" => 1691280
                            "created_at" => "2026-04-10 13:58:26"
                            "updated_at" => null
                            "edition" => Illuminate\Database\Eloquent\Collection {#1246
                              #items: array:1 [
                                0 => App\Models\Edition {#1095}
                              ]
                              #escapeWhenCastingToString: false
                            }
                            "task" => array:2 [
                              "refs" => "1319468"
                              "type" => "task"
                            ]
                            "text" => "<p><strong>Дано:</strong></p><p>$m$ – масса шарика<br>$a$ – ускорение тележки (горизонтальное)<br>$g$ – ускорение свободного падения</p><p>Все величины считаются заданными в системе СИ.</p><p><strong>Найти:</strong></p><p>$\alpha$ – угол отклонения нити от вертикали<br>$T$ – сила натяжения нити</p><p><strong>Решение:</strong></p><p>Рассмотрим шарик в инерциальной системе отсчета, связанной с землей. На шарик действуют две силы:</p><p><strong>1.</strong> Сила тяжести $\vec{F_g} = m\vec{g}$, направленная вертикально вниз.</p><p><strong>2.</strong> Сила натяжения нити $\vec{T}$, направленная вдоль нити под углом $\alpha$ к вертикали.</p><p>Поскольку шарик движется вместе с тележкой, он имеет горизонтальное ускорение $\vec{a}$. Согласно второму закону Ньютона, равнодействующая всех сил, действующих на шарик, равна произведению его массы на ускорение:</p><p>$\vec{T} + m\vec{g} = m\vec{a}$</p><p>Для решения этого векторного уравнения разложим силы на компоненты. Введем систему координат: ось <em>Ox</em> направим горизонтально в сторону ускорения, а ось <em>Oy</em> – вертикально вверх.</p><p>Запишем проекции второго закона Ньютона на эти оси:</p><p>На ось <em>Ox</em>: $T_x = ma$<br>Из геометрии рисунка видно, что $T_x = T \sin(\alpha)$.<br>Следовательно, $T \sin(\alpha) = ma$ (1)</p><p>На ось <em>Oy</em>: $T_y - mg = 0$ (так как по вертикали шарик не движется, его ускорение в этой проекции равно нулю).<br>Из геометрии рисунка $T_y = T \cos(\alpha)$.<br>Следовательно, $T \cos(\alpha) = mg$ (2)</p><p>Мы получили систему из двух уравнений с двумя неизвестными, $\alpha$ и $T$.</p><p><strong>1.</strong> Найдем угол $\alpha$.</p><p>Разделим уравнение (1) на уравнение (2):</p><p>$\frac{T \sin(\alpha)}{T \cos(\alpha)} = \frac{ma}{mg}$</p><p>Сократив $T$ и $m$, получим:</p><p>$\tan(\alpha) = \frac{a}{g}$</p><p>Отсюда угол отклонения нити равен:</p><p>$\alpha = \arctan(\frac{a}{g})$</p><p><strong>2.</strong> Найдем силу натяжения нити $T$.</p><p>Возведем в квадрат оба уравнения (1) и (2) и сложим их:</p><p>$(T \sin(\alpha))^2 + (T \cos(\alpha))^2 = (ma)^2 + (mg)^2$</p><p>$T^2 \sin^2(\alpha) + T^2 \cos^2(\alpha) = m^2 a^2 + m^2 g^2$</p><p>Вынесем $T^2$ и $m^2$ за скобки:</p><p>$T^2 (\sin^2(\alpha) + \cos^2(\alpha)) = m^2 (a^2 + g^2)$</p><p>Используя основное тригонометрическое тождество $\sin^2(\alpha) + \cos^2(\alpha) = 1$, получаем:</p><p>$T^2 = m^2 (g^2 + a^2)$</p><p>Извлекая квадратный корень, находим модуль силы натяжения нити:</p><p>$T = \sqrt{m^2 (g^2 + a^2)} = m\sqrt{g^2 + a^2}$</p><p><strong>Ответ:</strong> Угол отклонения нити от вертикали $\alpha = \arctan(\frac{a}{g})$, сила натяжения нити $T = m\sqrt{g^2 + a^2}$.</p>"
                          ]
                          #original: array:6 [
                            "id" => 1691280
                            "created_at" => "2026-04-10 13:58:26"
                            "updated_at" => null
                            "edition" => Illuminate\Database\Eloquent\Collection {#1246}
                            "task" => array:2 [
                              "refs" => "1319468"
                              "type" => "task"
                            ]
                            "text" => "<p><strong>Дано:</strong></p><p>$m$ – масса шарика<br>$a$ – ускорение тележки (горизонтальное)<br>$g$ – ускорение свободного падения</p><p>Все величины считаются заданными в системе СИ.</p><p><strong>Найти:</strong></p><p>$\alpha$ – угол отклонения нити от вертикали<br>$T$ – сила натяжения нити</p><p><strong>Решение:</strong></p><p>Рассмотрим шарик в инерциальной системе отсчета, связанной с землей. На шарик действуют две силы:</p><p><strong>1.</strong> Сила тяжести $\vec{F_g} = m\vec{g}$, направленная вертикально вниз.</p><p><strong>2.</strong> Сила натяжения нити $\vec{T}$, направленная вдоль нити под углом $\alpha$ к вертикали.</p><p>Поскольку шарик движется вместе с тележкой, он имеет горизонтальное ускорение $\vec{a}$. Согласно второму закону Ньютона, равнодействующая всех сил, действующих на шарик, равна произведению его массы на ускорение:</p><p>$\vec{T} + m\vec{g} = m\vec{a}$</p><p>Для решения этого векторного уравнения разложим силы на компоненты. Введем систему координат: ось <em>Ox</em> направим горизонтально в сторону ускорения, а ось <em>Oy</em> – вертикально вверх.</p><p>Запишем проекции второго закона Ньютона на эти оси:</p><p>На ось <em>Ox</em>: $T_x = ma$<br>Из геометрии рисунка видно, что $T_x = T \sin(\alpha)$.<br>Следовательно, $T \sin(\alpha) = ma$ (1)</p><p>На ось <em>Oy</em>: $T_y - mg = 0$ (так как по вертикали шарик не движется, его ускорение в этой проекции равно нулю).<br>Из геометрии рисунка $T_y = T \cos(\alpha)$.<br>Следовательно, $T \cos(\alpha) = mg$ (2)</p><p>Мы получили систему из двух уравнений с двумя неизвестными, $\alpha$ и $T$.</p><p><strong>1.</strong> Найдем угол $\alpha$.</p><p>Разделим уравнение (1) на уравнение (2):</p><p>$\frac{T \sin(\alpha)}{T \cos(\alpha)} = \frac{ma}{mg}$</p><p>Сократив $T$ и $m$, получим:</p><p>$\tan(\alpha) = \frac{a}{g}$</p><p>Отсюда угол отклонения нити равен:</p><p>$\alpha = \arctan(\frac{a}{g})$</p><p><strong>2.</strong> Найдем силу натяжения нити $T$.</p><p>Возведем в квадрат оба уравнения (1) и (2) и сложим их:</p><p>$(T \sin(\alpha))^2 + (T \cos(\alpha))^2 = (ma)^2 + (mg)^2$</p><p>$T^2 \sin^2(\alpha) + T^2 \cos^2(\alpha) = m^2 a^2 + m^2 g^2$</p><p>Вынесем $T^2$ и $m^2$ за скобки:</p><p>$T^2 (\sin^2(\alpha) + \cos^2(\alpha)) = m^2 (a^2 + g^2)$</p><p>Используя основное тригонометрическое тождество $\sin^2(\alpha) + \cos^2(\alpha) = 1$, получаем:</p><p>$T^2 = m^2 (g^2 + a^2)$</p><p>Извлекая квадратный корень, находим модуль силы натяжения нити:</p><p>$T = \sqrt{m^2 (g^2 + a^2)} = m\sqrt{g^2 + a^2}$</p><p><strong>Ответ:</strong> Угол отклонения нити от вертикали $\alpha = \arctan(\frac{a}{g})$, сила натяжения нити $T = m\sqrt{g^2 + a^2}$.</p>"
                          ]
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                          #dateFormat: null
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                    "book" => Illuminate\Database\Eloquent\Collection {#1240
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                    "page" => array:2 [
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                    "parent_branches" => Illuminate\Database\Eloquent\Collection {#1232}
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                    "book" => Illuminate\Database\Eloquent\Collection {#1240}
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                  #guarded: array:1 [
                    0 => "*"
                  ]
                }
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                  #connection: "mysql"
                  #table: "tasks"
                  #primaryKey: "id"
                  #keyType: "int"
                  +incrementing: true
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                  #escapeWhenCastingToString: false
                  #attributes: array:24 [
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                    "created_at" => "2026-04-10 13:58:26"
                    "updated_at" => null
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                    "field_page_end" => "58"
                    "field_url" => "/10-klass/fizika/gelfgat-zadachnik/08-2"
                    "field_display_title" => "8.2"
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                      #escapeWhenCastingToString: false
                    }
                    "parent_branches" => Illuminate\Database\Eloquent\Collection {#1236
                      #items: array:4 [
                        0 => App\Models\Branch {#1121}
                        1 => App\Models\Branch {#1125}
                        2 => App\Models\Branch {#1129}
                        3 => App\Models\Branch {#1133}
                      ]
                      #escapeWhenCastingToString: false
                    }
                    "content" => Illuminate\Database\Eloquent\Collection {#1239
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                        0 => App\Models\Element {#1102}
                        1 => App\Models\Element {#1094}
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                      #escapeWhenCastingToString: false
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                    "next" => array:2 [
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                    "previous" => array:2 [
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                      "type" => "task"
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                    "book" => Illuminate\Database\Eloquent\Collection {#1237
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                      #escapeWhenCastingToString: false
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                    "page" => array:2 [
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                  ]
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                    "created_at" => "2026-04-10 13:58:26"
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                    "field_outside_task" => "0"
                    "field_task_type" => Illuminate\Database\Eloquent\Collection {#1233}
                    "field_metatags_title" => null
                    "field_metatags_description" => null
                    "field_h1" => null
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№8.2 (с. 57)
Условие. №8.2 (с. 57)
скриншот условия
Физика, 10-11 класс Задачник, авторы: Гельфгат Илья Маркович, Генденштейн Лев Элевич, Кирик Леонид Анатольевич, издательство Илекса, Москва, 2008, красного цвета, страница 57, номер 8.2, Условие
Физика, 10-11 класс Задачник, авторы: Гельфгат Илья Маркович, Генденштейн Лев Элевич, Кирик Леонид Анатольевич, издательство Илекса, Москва, 2008, красного цвета, страница 57, номер 8.2, Условие (продолжение 2)

8.2. К концам шнура, перекинутого через блок, подвешены грузы с массами $m_1 = 100 \text{ г}$ и $m_2 = 150 \text{ г}$. Найдите ускорение грузов, силу натяжения шнура $\text{T}$ и показание $\text{F}$ динамометра, на котором висит блок.

☑ 2 м/с$^2$; 1,2 Н; 2,4 Н.

Решение. Благодаря нерастяжимости шнура перемещения обоих грузов одинаковы по величине; значит, одинаковы по величине и их ускорения: $a_1 = a_2 = a$. Пренебрегая массами шнура и блока, а также трением в блоке, можно считать силу $\text{T}$ натяжения шнура всюду одинаковой. На рисунке а показаны действующие на грузы силы. Запишем уравнения второго закона Ньютона для каждого из грузов в проекции на ось $\text{y}$:

$\begin{cases} m_1 a = -m_1 g + T \\ -m_2 a = -m_2 g + T \end{cases}$

Отсюда $a = \frac{m_2 - m_1}{m_2 + m_1} g = 2,0 \text{ (м/с}^2\text{)}$, $T = \frac{2m_1 m_2 g}{m_1 + m_2} = 1,2 \text{ (Н)}$.

Для нахождения силы $\text{F}$ упругости пружины динамометра надо рассмотреть силы, действующие на блок (см. рис. б).

Из условия равновесия блока получаем, что $F = 2T = 2,4 \text{ (Н)}$. На примере данной задачи покажем два эффективных метода проверки полученного результата.

Первый из них — проверка на симметрию. Очевидно, если поменять грузы местами, натяжение шнура и величина ускорения грузов не должны измениться. Полученные для $\text{a}$ и $\text{T}$ выражения этому требованию удовлетворяют (при замене $m_1 \leftrightarrow m_2$, значение $\text{T}$ не изменяется, а ускорение меняет только знак).

Второй метод — проверка на частные и предельные случаи. Например, при $m_1 = m_2 = m$ ускорение должно быть равно нулю, а $T = mg$. При $m_1 \rightarrow 0$ должно быть $a \rightarrow g$, $T \rightarrow 0$ (груз 2 свободно падает и поэтому находится в состоянии невесомости). Полученные формулы удовлетворяют и этим требованиям. Обратим внимание на то, что вес обоих грузов одинаков, как бы сильно ни отличались их массы: ведь оба груза действуют на шнур с одинаковыми силами. Дело в том, что вес меньшего груза увеличивается (ускорение этого груза направлено вверх), а вес большего груза уменьшается (ускорение этого груза направлено вниз).

Решение. №8.2 (с. 57)

Дано:

$m_1 = 100$ г

$m_2 = 150$ г

В системе СИ:

$m_1 = 0.1$ кг

$m_2 = 0.15$ кг

Ускорение свободного падения $g \approx 10 \, \text{м/с}^2$.

Найти:

$a$ — ускорение грузов;

$T$ — сила натяжения шнура;

$F$ — показание динамометра.

Решение:

Данная система представляет собой машину Атвуда. Будем считать шнур нерастяжимым и невесомым, а блок — идеальным (невесомым и без трения).

1. Ускорение грузов (a)

Поскольку $m_2 > m_1$, груз $m_2$ будет опускаться, а груз $m_1$ — подниматься. Из-за нерастяжимости шнура ускорения обоих грузов будут одинаковы по модулю. Обозначим модуль ускорения как $a$.

Запишем второй закон Ньютона для каждого груза в проекции на вертикальную ось $y$, направленную вверх:

Для груза $m_1$: $m_1a = T - m_1g$

Для груза $m_2$: $-m_2a = T - m_2g$ (ускорение направлено вниз, поэтому проекция отрицательна)

Получаем систему уравнений:

$$ \begin{cases} T = m_1a + m_1g \\ T = m_2g - m_2a \end{cases} $$

Приравняем правые части уравнений, чтобы найти ускорение $a$:

$m_1a + m_1g = m_2g - m_2a$

$a(m_1 + m_2) = g(m_2 - m_1)$

$a = \frac{m_2 - m_1}{m_1 + m_2}g$

Подставим числовые значения:

$a = \frac{0.15 \, \text{кг} - 0.1 \, \text{кг}}{0.15 \, \text{кг} + 0.1 \, \text{кг}} \cdot 10 \, \frac{\text{м}}{\text{с}^2} = \frac{0.05}{0.25} \cdot 10 \, \frac{\text{м}}{\text{с}^2} = 0.2 \cdot 10 \, \frac{\text{м}}{\text{с}^2} = 2 \, \frac{\text{м}}{\text{с}^2}$

Ответ: Ускорение грузов равно $2 \, \text{м/с}^2$.

2. Сила натяжения шнура (T)

Для нахождения силы натяжения шнура $T$ подставим найденное значение ускорения $a$ в любое из уравнений системы. Воспользуемся первым:

$T = m_1(a + g)$

Подставим числовые значения:

$T = 0.1 \, \text{кг} \cdot (2 \, \frac{\text{м}}{\text{с}^2} + 10 \, \frac{\text{м}}{\text{с}^2}) = 0.1 \, \text{кг} \cdot 12 \, \frac{\text{м}}{\text{с}^2} = 1.2 \, \text{Н}$

Ответ: Сила натяжения шнура равна $1.2 \, \text{Н}$.

3. Показание динамометра (F)

Динамометр измеряет силу, с которой система "блок-грузы" действует на него. Эта сила равна по модулю силе упругости $F$, которая уравновешивает силы, действующие на блок со стороны шнура. На невесомый блок действуют две силы натяжения $T$, направленные вертикально вниз (по одной от каждого конца шнура).

Из условия равновесия блока следует, что показание динамометра $F$ равно сумме сил натяжения:

$F = T + T = 2T$

Подставим найденное значение $T$:

$F = 2 \cdot 1.2 \, \text{Н} = 2.4 \, \text{Н}$

Ответ: Показание динамометра равно $2.4 \, \text{Н}$.

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