Номер 11, страница 45, часть 2 - гдз по физике 9 класс рабочая тетрадь Грачев, Погожев

Авторы: Грачев А. В., Погожев В. А., Боков П. Ю., Вишнякова Е. А.

Тип: рабочая тетрадь

Издательство: Просвещение

Год издания: 2021 - 2026

Часть: 2

Цвет обложки: синий

ISBN: 978-5-09-098826-1 (ч.1) 978-5-09-098880-3 (ч.2) 978-5-09-098881-0 (ч.3)

Часть 2. Глава 5. Статика. Параграф 30. Применение условий равновесия при решении задач статики - номер 11, страница 45.

App\Models\Task {#1030 // resources/views/models/task/default.blade.php
  #connection: "mysql"
  #table: "tasks"
  #primaryKey: "id"
  #keyType: "int"
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  #perPage: 15
  +exists: true
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  #escapeWhenCastingToString: false
  #attributes: array:24 [
    "id" => 1435123
    "created_at" => "2026-04-10 13:58:26"
    "updated_at" => null
    "field_page_start" => "45"
    "field_page_end" => null
    "field_url" => "/9-klass/fizika/grachev-rabochaya-tetrad/30-11"
    "field_display_title" => "11"
    "field_outside_task" => null
    "field_task_type" => Illuminate\Database\Eloquent\Collection {#1037
      #items: array:1 [
        0 => App\Models\Term {#1036
          #connection: "mysql"
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          #primaryKey: "id"
          #keyType: "int"
          +incrementing: false
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          #attributes: array:6 [
            "id" => 26
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            "updated_at" => null
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              "field_accusative_case" => "номер"
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              "field_genitive_case" => "номера"
              "field_nominative_case" => "номер"
              "field_prepositional_case" => "номере"
            ]
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          ]
          #original: array:6 [
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        0 => App\Models\Branch {#1045
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            "id" => 1434829
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                0 => App\Models\Term {#1047
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                      "field_prepositional_case" => "Части"
                    ]
                    "field_page_check_not_needed" => "1"
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                  ]
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                0 => App\Models\Book {#1049
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                    "id" => 1203
                    "created_at" => "2026-04-10 13:58:26"
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                      #items: array:1 [
                        0 => App\Models\Term {#1048
                          #connection: "mysql"
                          #table: "terms"
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                            "id" => 6493
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                            "updated_at" => null
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                            "field_abbreviated_name" => null
                            "field_cases" => array:6 [
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                            ]
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                            "field_short_name" => null
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                          #original: array:10 [
                            "id" => 6493
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                      #items: array:1 [
                        0 => App\Models\Term {#1053
                          #connection: "mysql"
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                          #primaryKey: "id"
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                            "created_at" => "2026-04-10 13:58:26"
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                      #items: array:1 [
                        0 => App\Models\Term {#1055
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                          #table: "terms"
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                          +preventsLazyLoading: false
                          #perPage: 15
                          +exists: true
                          +wasRecentlyCreated: false
                          #escapeWhenCastingToString: false
                          #attributes: array:10 [
                            "id" => 6736
                            "created_at" => "2026-04-10 13:58:26"
                            "updated_at" => null
                            "name" => "рабочая тетрадь"
                            "field_book_type_foreign" => null
                            "field_cases" => array:6 [
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                              "field_creative_case" => "рабочей тетрадью"
                              "field_dative_case" => "рабочей тетради"
                              "field_genitive_case" => "рабочей тетради"
                              "field_nominative_case" => "рабочая тетрадь"
                              "field_prepositional_case" => "рабочей тетради"
                            ]
                            "field_plural_form" => "рабочие тетради"
                            "field_short_name" => "рт"
                            "field_short_name_foreign" => null
                            "field_translit" => "rabochaya tetrad"
                          ]
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                            "id" => 6736
                            "created_at" => "2026-04-10 13:58:26"
                            "updated_at" => null
                            "name" => "рабочая тетрадь"
                            "field_book_type_foreign" => null
                            "field_cases" => array:6 [
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                              "field_genitive_case" => "рабочей тетради"
                              "field_nominative_case" => "рабочая тетрадь"
                              "field_prepositional_case" => "рабочей тетради"
                            ]
                            "field_plural_form" => "рабочие тетради"
                            "field_short_name" => "рт"
                            "field_short_name_foreign" => null
                            "field_translit" => "rabochaya tetrad"
                          ]
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                          #classCastCache: []
                          #attributeCastCache: []
                          #dateFormat: null
                          #appends: []
                          #dispatchesEvents: []
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                          #relations: []
                          #touches: []
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                          #hidden: []
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                            0 => "*"
                          ]
                        }
                      ]
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                    }
                    "field_country" => Illuminate\Database\Eloquent\Collection {#1064
                      #items: array:1 [
                        0 => App\Models\Term {#1065
                          #connection: "mysql"
                          #table: "terms"
                          #primaryKey: "id"
                          #keyType: "int"
                          +incrementing: false
                          #with: []
                          #withCount: []
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                          +exists: true
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                          #attributes: array:6 [
                            "id" => 9
                            "created_at" => "2026-04-10 13:58:26"
                            "updated_at" => null
                            "name" => "Россия"
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                              "field_prepositional_case" => null
                            ]
                            "field_translit" => "rossiya"
                          ]
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                            "created_at" => "2026-04-10 13:58:26"
                            "updated_at" => null
                            "name" => "Россия"
                            "field_cases" => array:6 [
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                            ]
                            "field_translit" => "rossiya"
                          ]
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                          #dateFormat: null
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                          #dispatchesEvents: []
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                          #relations: []
                          #touches: []
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                          #hidden: []
                          #visible: []
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                            0 => "*"
                          ]
                        }
                      ]
                      #escapeWhenCastingToString: false
                    }
                    "field_city" => Illuminate\Database\Eloquent\Collection {#1066
                      #items: array:1 [
                        0 => App\Models\Term {#1067
                          #connection: "mysql"
                          #table: "terms"
                          #primaryKey: "id"
                          #keyType: "int"
                          +incrementing: false
                          #with: []
                          #withCount: []
                          +preventsLazyLoading: false
                          #perPage: 15
                          +exists: true
                          +wasRecentlyCreated: false
                          #escapeWhenCastingToString: false
                          #attributes: array:6 [
                            "id" => 15
                            "created_at" => "2026-04-10 13:58:26"
                            "updated_at" => null
                            "name" => "Москва"
                            "field_cases" => array:6 [
                              "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"
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                            ]
                            "field_translit" => "moskva"
                          ]
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                          #dateFormat: null
                          #appends: []
                          #dispatchesEvents: []
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                          #relations: []
                          #touches: []
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                          #hidden: []
                          #visible: []
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                            0 => "*"
                          ]
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                      ]
                      #escapeWhenCastingToString: false
                    }
                    "field_series" => Illuminate\Database\Eloquent\Collection {#1068
                      #items: []
                      #escapeWhenCastingToString: false
                    }
                    "field_umk" => Illuminate\Database\Eloquent\Collection {#1069
                      #items: []
                      #escapeWhenCastingToString: false
                    }
                    "field_level_of_education" => Illuminate\Database\Eloquent\Collection {#1070
                      #items: []
                      #escapeWhenCastingToString: false
                    }
                    "field_standart_of_education" => Illuminate\Database\Eloquent\Collection {#1071
                      #items: array:1 [
                        0 => App\Models\Term {#1072
                          #connection: "mysql"
                          #table: "terms"
                          #primaryKey: "id"
                          #keyType: "int"
                          +incrementing: false
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                          #withCount: []
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                          +wasRecentlyCreated: false
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                          #attributes: array:10 [
                            "id" => 6706
                            "created_at" => "2026-04-10 13:58:26"
                            "updated_at" => null
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                            "field_cases" => array:6 [
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                            ]
                            "field_color" => null
                            "field_end_year" => "2022"
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                            "field_translit" => "fgos-old"
                            "field_type" => null
                          ]
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                            "id" => 6706
                            "created_at" => "2026-04-10 13:58:26"
                            "updated_at" => null
                            "name" => "ФГОС (старый)"
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                            ]
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                          ]
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                      ]
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                    }
                    "field_publication_number" => "6"
                    "field_publication_type" => Illuminate\Database\Eloquent\Collection {#1073
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                        0 => App\Models\Term {#1074
                          #connection: "mysql"
                          #table: "terms"
                          #primaryKey: "id"
                          #keyType: "int"
                          +incrementing: false
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                          #withCount: []
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                          +exists: true
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                          #attributes: array:6 [
                            "id" => 33
                            "created_at" => "2026-04-10 13:58:26"
                            "updated_at" => null
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                            "field_cases" => array:6 [
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                            ]
                            "field_translit" => "stereotipnoe"
                          ]
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                            "id" => 33
                            "created_at" => "2026-04-10 13:58:26"
                            "updated_at" => null
                            "name" => "стереотипное"
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                            ]
                            "field_translit" => "stereotipnoe"
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                          #attributeCastCache: []
                          #dateFormat: null
                          #appends: []
                          #dispatchesEvents: []
                          #observables: []
                          #relations: []
                          #touches: []
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                          #hidden: []
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                          #guarded: array:1 [
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                        }
                      ]
                      #escapeWhenCastingToString: false
                    }
                    "field_under_the_edition" => Illuminate\Database\Eloquent\Collection {#1075
                      #items: []
                      #escapeWhenCastingToString: false
                    }
                    "field_under_the_edition_degree" => null
                    "field_cover_description" => null
                    "field_publication_year" => "2021"
                    "field_publication_year_until" => null
                    "field_part" => "1, 2, 3"
                    "field_part_writing" => "Часть"
                    "field_second_foreign_language" => null
                    "field_for_whom" => "Учебное издание"
                    "field_allowed" => null
                    "field_reserve_field" => null
                    "field_link_to_source" => null
                    "field_tasks_count" => "594"
                    "field_priority" => null
                    "field_default_folder" => "/fizika_09/grachev-rt/"
                    "field_isbn" => "978-5-09-098826-1 (ч.1) 978-5-09-098880-3 (ч.2) 978-5-09-098881-0 (ч.3)"
                    "field_cover" => array:3 [
                      0 => "/media/fizika_09/grachev-rt/covers/cover1.webp?ts=1759003248"
                      1 => "/media/fizika_09/grachev-rt/covers/cover2.webp?ts=1759003248"
                      2 => "/media/fizika_09/grachev-rt/covers/cover3.webp?ts=1759003248"
                    ]
                    "field_cover_alts" => array:3 [
                      0 => ""
                      1 => ""
                      2 => ""
                    ]
                    "field_covers" => array:3 [
                      0 => array:4 [
                        "path" => "/media/fizika_09/grachev-rt/covers/cover1.webp?ts=1759003248"
                        "alt" => ""
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                      ]
                      1 => array:4 [
                        "path" => "/media/fizika_09/grachev-rt/covers/cover2.webp?ts=1759003248"
                        "alt" => ""
                        "width" => "2265"
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                      ]
                      2 => array:4 [
                        "path" => "/media/fizika_09/grachev-rt/covers/cover3.webp?ts=1759003248"
                        "alt" => ""
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                      ]
                    ]
                    "field_popular_book" => "0"
                    "field_recommended_books" => Illuminate\Database\Eloquent\Collection {#1076
                      #items: []
                      #escapeWhenCastingToString: false
                    }
                    "field_new_book" => Illuminate\Database\Eloquent\Collection {#1077
                      #items: []
                      #escapeWhenCastingToString: false
                    }
                    "field_old_book" => Illuminate\Database\Eloquent\Collection {#1078
                      #items: []
                      #escapeWhenCastingToString: false
                    }
                    "field_url" => "/9-klass/fizika/grachev-rabochaya-tetrad"
                    "field_cover_color" => 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:6 [
                            "id" => 49
                            "created_at" => "2026-04-10 13:58:26"
                            "updated_at" => null
                            "name" => "синий"
                            "field_cases" => array:6 [
                              "field_accusative_case" => null
                              "field_creative_case" => null
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                              "field_genitive_case" => null
                              "field_nominative_case" => null
                              "field_prepositional_case" => null
                            ]
                            "field_translit" => "siniy"
                          ]
                          #original: array:6 [
                            "id" => 49
                            "created_at" => "2026-04-10 13:58:26"
                            "updated_at" => null
                            "name" => "синий"
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                            ]
                            "field_translit" => "siniy"
                          ]
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                          #dateFormat: null
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                      ]
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                    }
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                    "field_metatags_description" => null
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                    "breadcrumbs" => array:3 [
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                    ]
                  ]
                  #original: array:50 [
                    "id" => 1203
                    "created_at" => "2026-04-10 13:58:26"
                    "updated_at" => null
                    "field_tree_default_status" => "tasks"
                    "field_pages_status" => null
                    "field_subject" => Illuminate\Database\Eloquent\Collection {#1051}
                    "field_class" => Illuminate\Database\Eloquent\Collection {#1052}
                    "field_publisher" => Illuminate\Database\Eloquent\Collection {#1054}
                    "field_author" => Illuminate\Database\Eloquent\Collection {#1056}
                    "field_author_foreign" => Illuminate\Database\Eloquent\Collection {#1061}
                    "field_book_type" => Illuminate\Database\Eloquent\Collection {#1062}
                    "field_country" => Illuminate\Database\Eloquent\Collection {#1064}
                    "field_city" => Illuminate\Database\Eloquent\Collection {#1066}
                    "field_series" => Illuminate\Database\Eloquent\Collection {#1068}
                    "field_umk" => Illuminate\Database\Eloquent\Collection {#1069}
                    "field_level_of_education" => Illuminate\Database\Eloquent\Collection {#1070}
                    "field_standart_of_education" => Illuminate\Database\Eloquent\Collection {#1071}
                    "field_publication_number" => "6"
                    "field_publication_type" => Illuminate\Database\Eloquent\Collection {#1073}
                    "field_under_the_edition" => Illuminate\Database\Eloquent\Collection {#1075}
                    "field_under_the_edition_degree" => null
                    "field_cover_description" => null
                    "field_publication_year" => "2021"
                    "field_publication_year_until" => null
                    "field_part" => "1, 2, 3"
                    "field_part_writing" => "Часть"
                    "field_second_foreign_language" => null
                    "field_for_whom" => "Учебное издание"
                    "field_allowed" => null
                    "field_reserve_field" => null
                    "field_link_to_source" => null
                    "field_tasks_count" => "594"
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                    "field_default_folder" => "/fizika_09/grachev-rt/"
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                    "field_cover" => array:3 [
                      0 => "/media/fizika_09/grachev-rt/covers/cover1.webp?ts=1759003248"
                      1 => "/media/fizika_09/grachev-rt/covers/cover2.webp?ts=1759003248"
                      2 => "/media/fizika_09/grachev-rt/covers/cover3.webp?ts=1759003248"
                    ]
                    "field_cover_alts" => array:3 [
                      0 => ""
                      1 => ""
                      2 => ""
                    ]
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                      0 => array:4 [
                        "path" => "/media/fizika_09/grachev-rt/covers/cover1.webp?ts=1759003248"
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                      ]
                      1 => array:4 [
                        "path" => "/media/fizika_09/grachev-rt/covers/cover2.webp?ts=1759003248"
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                      ]
                      2 => array:4 [
                        "path" => "/media/fizika_09/grachev-rt/covers/cover3.webp?ts=1759003248"
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                      ]
                    ]
                    "field_popular_book" => "0"
                    "field_recommended_books" => Illuminate\Database\Eloquent\Collection {#1076}
                    "field_new_book" => Illuminate\Database\Eloquent\Collection {#1077}
                    "field_old_book" => Illuminate\Database\Eloquent\Collection {#1078}
                    "field_url" => "/9-klass/fizika/grachev-rabochaya-tetrad"
                    "field_cover_color" => Illuminate\Database\Eloquent\Collection {#1079}
                    "field_metatags_title" => null
                    "field_metatags_description" => null
                    "field_h1" => null
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                    "breadcrumbs" => array:3 [
                      "class" => 380
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                    ]
                  ]
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                  #attributeCastCache: []
                  #dateFormat: null
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                  #touches: []
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                  #hidden: []
                  #visible: []
                  #fillable: []
                  #guarded: array:1 [
                    0 => "*"
                  ]
                }
              ]
              #escapeWhenCastingToString: false
            }
            "branch_parent" => Illuminate\Database\Eloquent\Collection {#1081
              #items: []
              #escapeWhenCastingToString: false
            }
          ]
          #original: array:24 [
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            "created_at" => "2026-04-10 13:58:26"
            "updated_at" => null
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            "field_url" => null
            "field_branch_type" => Illuminate\Database\Eloquent\Collection {#1050}
            "field_page_start" => "3"
            "field_branch_display" => "0"
            "field_branch_expanded" => "0"
            "field_display_branch_in_title" => "1"
            "field_display_task_interval" => "0"
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            "field_branch_title_in_content" => "0"
            "field_navigation_title" => null
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            "field_metatags_description" => null
            "field_h1" => null
            "field_description_top" => null
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            "field_branch_cover" => []
            "field_branch_covers" => []
            "book" => Illuminate\Database\Eloquent\Collection {#1083}
            "branch_parent" => Illuminate\Database\Eloquent\Collection {#1081}
          ]
          #changes: []
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          #attributeCastCache: []
          #dateFormat: null
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          #dispatchesEvents: []
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          #touches: []
          +timestamps: true
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          #hidden: []
          #visible: []
          #fillable: []
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            0 => "*"
          ]
        }
      ]
      #escapeWhenCastingToString: false
    }
    "parent_branches" => Illuminate\Database\Eloquent\Collection {#1114
      #items: array:3 [
        0 => App\Models\Branch {#1124
          #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" => 1434829
            "created_at" => "2026-04-10 13:58:26"
            "updated_at" => null
            "field_display_title" => null
            "field_branch_order" => "2"
            "field_url" => null
            "field_branch_type" => Illuminate\Database\Eloquent\Collection {#1125
              #items: array:1 [
                0 => App\Models\Term {#1047}
              ]
              #escapeWhenCastingToString: false
            }
            "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 {#1126
              #items: array:1 [
                0 => App\Models\Book {#1049}
              ]
              #escapeWhenCastingToString: false
            }
            "branch_parent" => Illuminate\Database\Eloquent\Collection {#1127
              #items: []
              #escapeWhenCastingToString: false
            }
          ]
          #original: array:24 [
            "id" => 1434829
            "created_at" => "2026-04-10 13:58:26"
            "updated_at" => null
            "field_display_title" => null
            "field_branch_order" => "2"
            "field_url" => null
            "field_branch_type" => Illuminate\Database\Eloquent\Collection {#1125}
            "field_page_start" => "3"
            "field_branch_display" => "0"
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            "field_display_branch_page" => "1"
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            "field_metatags_description" => null
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            "field_description_top" => null
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            "field_branch_cover" => []
            "field_branch_covers" => []
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          #attributeCastCache: []
          #dateFormat: null
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          #touches: []
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          #hidden: []
          #visible: []
          #fillable: []
          #guarded: array:1 [
            0 => "*"
          ]
        }
        1 => App\Models\Branch {#1128
          #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" => 1434838
            "created_at" => "2026-04-10 13:58:26"
            "updated_at" => null
            "field_display_title" => "Статика"
            "field_branch_order" => "5"
            "field_url" => null
            "field_branch_type" => Illuminate\Database\Eloquent\Collection {#1132
              #items: array:1 [
                0 => App\Models\Term {#1129
                  #connection: "mysql"
                  #table: "terms"
                  #primaryKey: "id"
                  #keyType: "int"
                  +incrementing: false
                  #with: []
                  #withCount: []
                  +preventsLazyLoading: false
                  #perPage: 15
                  +exists: true
                  +wasRecentlyCreated: false
                  #escapeWhenCastingToString: false
                  #attributes: array:7 [
                    "id" => 29
                    "created_at" => "2026-04-10 13:58:26"
                    "updated_at" => null
                    "name" => "Глава"
                    "field_cases" => array:6 [
                      "field_accusative_case" => "Главу"
                      "field_creative_case" => "Главой"
                      "field_dative_case" => "Главе"
                      "field_genitive_case" => "Главы"
                      "field_nominative_case" => "Глава"
                      "field_prepositional_case" => "Главе"
                    ]
                    "field_page_check_not_needed" => null
                    "field_short_name" => null
                  ]
                  #original: array:7 [
                    "id" => 29
                    "created_at" => "2026-04-10 13:58:26"
                    "updated_at" => null
                    "name" => "Глава"
                    "field_cases" => array:6 [
                      "field_accusative_case" => "Главу"
                      "field_creative_case" => "Главой"
                      "field_dative_case" => "Главе"
                      "field_genitive_case" => "Главы"
                      "field_nominative_case" => "Глава"
                      "field_prepositional_case" => "Главе"
                    ]
                    "field_page_check_not_needed" => null
                    "field_short_name" => null
                  ]
                  #changes: []
                  #casts: []
                  #classCastCache: []
                  #attributeCastCache: []
                  #dateFormat: null
                  #appends: []
                  #dispatchesEvents: []
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                  #touches: []
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                  #hidden: []
                  #visible: []
                  #fillable: []
                  #guarded: array:1 [
                    0 => "*"
                  ]
                }
              ]
              #escapeWhenCastingToString: false
            }
            "field_page_start" => "35"
            "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 {#1131
              #items: array:1 [
                0 => App\Models\Book {#1049}
              ]
              #escapeWhenCastingToString: false
            }
            "branch_parent" => Illuminate\Database\Eloquent\Collection {#1130
              #items: array:1 [
                0 => App\Models\Branch {#1045}
              ]
              #escapeWhenCastingToString: false
            }
          ]
          #original: array:24 [
            "id" => 1434838
            "created_at" => "2026-04-10 13:58:26"
            "updated_at" => null
            "field_display_title" => "Статика"
            "field_branch_order" => "5"
            "field_url" => null
            "field_branch_type" => Illuminate\Database\Eloquent\Collection {#1132}
            "field_page_start" => "35"
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            "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 {#1131}
            "branch_parent" => Illuminate\Database\Eloquent\Collection {#1130}
          ]
          #changes: []
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          #classCastCache: []
          #attributeCastCache: []
          #dateFormat: null
          #appends: []
          #dispatchesEvents: []
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          #relations: []
          #touches: []
          +timestamps: true
          +usesUniqueIds: false
          #hidden: []
          #visible: []
          #fillable: []
          #guarded: array:1 [
            0 => "*"
          ]
        }
        2 => App\Models\Branch {#1133
          #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" => 1434840
            "created_at" => "2026-04-10 13:58:26"
            "updated_at" => null
            "field_display_title" => "Применение условий равновесия при решении задач статики"
            "field_branch_order" => "30"
            "field_url" => null
            "field_branch_type" => Illuminate\Database\Eloquent\Collection {#1137
              #items: array:1 [
                0 => App\Models\Term {#1134
                  #connection: "mysql"
                  #table: "terms"
                  #primaryKey: "id"
                  #keyType: "int"
                  +incrementing: false
                  #with: []
                  #withCount: []
                  +preventsLazyLoading: false
                  #perPage: 15
                  +exists: true
                  +wasRecentlyCreated: false
                  #escapeWhenCastingToString: false
                  #attributes: array:7 [
                    "id" => 32
                    "created_at" => "2026-04-10 13:58:26"
                    "updated_at" => null
                    "name" => "Параграф"
                    "field_cases" => array:6 [
                      "field_accusative_case" => "Параграф"
                      "field_creative_case" => "Параграфом"
                      "field_dative_case" => "Параграфу"
                      "field_genitive_case" => "Параграфа"
                      "field_nominative_case" => "Параграф"
                      "field_prepositional_case" => "Параграфе"
                    ]
                    "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 [
                      "field_accusative_case" => "Параграф"
                      "field_creative_case" => "Параграфом"
                      "field_dative_case" => "Параграфу"
                      "field_genitive_case" => "Параграфа"
                      "field_nominative_case" => "Параграф"
                      "field_prepositional_case" => "Параграфе"
                    ]
                    "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" => "41"
            "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 {#1136
              #items: array:1 [
                0 => App\Models\Book {#1049}
              ]
              #escapeWhenCastingToString: false
            }
            "branch_parent" => Illuminate\Database\Eloquent\Collection {#1145
              #items: array:1 [
                0 => App\Models\Branch {#1144
                  #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" => 1434838
                    "created_at" => "2026-04-10 13:58:26"
                    "updated_at" => null
                    "field_display_title" => "Статика"
                    "field_branch_order" => "5"
                    "field_url" => null
                    "field_branch_type" => Illuminate\Database\Eloquent\Collection {#1146
                      #items: array:1 [ …1]
                      #escapeWhenCastingToString: false
                    }
                    "field_page_start" => "35"
                    "field_branch_display" => "0"
                    "field_branch_expanded" => "0"
                    "field_display_branch_in_title" => "1"
                    "field_display_task_interval" => "0"
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                    "field_branch_title_in_content" => "0"
                    "field_navigation_title" => null
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                    "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 {#1147
                      #items: array:1 [ …1]
                      #escapeWhenCastingToString: false
                    }
                    "branch_parent" => Illuminate\Database\Eloquent\Collection {#1148
                      #items: array:1 [ …1]
                      #escapeWhenCastingToString: false
                    }
                  ]
                  #original: array:24 [
                    "id" => 1434838
                    "created_at" => "2026-04-10 13:58:26"
                    "updated_at" => null
                    "field_display_title" => "Статика"
                    "field_branch_order" => "5"
                    "field_url" => null
                    "field_branch_type" => Illuminate\Database\Eloquent\Collection {#1146}
                    "field_page_start" => "35"
                    "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 {#1147}
                    "branch_parent" => Illuminate\Database\Eloquent\Collection {#1148}
                  ]
                  #changes: []
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                  #classCastCache: []
                  #attributeCastCache: []
                  #dateFormat: null
                  #appends: []
                  #dispatchesEvents: []
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                  #relations: []
                  #touches: []
                  +timestamps: true
                  +usesUniqueIds: false
                  #hidden: []
                  #visible: []
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                  #guarded: array:1 [
                    0 => "*"
                  ]
                }
              ]
              #escapeWhenCastingToString: false
            }
          ]
          #original: array:24 [
            "id" => 1434840
            "created_at" => "2026-04-10 13:58:26"
            "updated_at" => null
            "field_display_title" => "Применение условий равновесия при решении задач статики"
            "field_branch_order" => "30"
            "field_url" => null
            "field_branch_type" => Illuminate\Database\Eloquent\Collection {#1137}
            "field_page_start" => "41"
            "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 {#1136}
            "branch_parent" => Illuminate\Database\Eloquent\Collection {#1145}
          ]
          #changes: []
          #casts: []
          #classCastCache: []
          #attributeCastCache: []
          #dateFormat: null
          #appends: []
          #dispatchesEvents: []
          #observables: []
          #relations: []
          #touches: []
          +timestamps: true
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          #hidden: []
          #visible: []
          #fillable: []
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            0 => "*"
          ]
        }
      ]
      #escapeWhenCastingToString: false
    }
    "content" => Illuminate\Database\Eloquent\Collection {#1038
      #items: array:2 [
        0 => App\Models\Element {#1106
          #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" => 1698511
            "created_at" => "2026-04-10 13:58:26"
            "updated_at" => null
            "edition" => Illuminate\Database\Eloquent\Collection {#1098
              #items: array:1 [
                0 => App\Models\Edition {#1104
                  #connection: "mysql"
                  #table: "editions"
                  #primaryKey: "id"
                  #keyType: "int"
                  +incrementing: false
                  #with: []
                  #withCount: []
                  +preventsLazyLoading: false
                  #perPage: 15
                  +exists: true
                  +wasRecentlyCreated: false
                  #escapeWhenCastingToString: false
                  #attributes: array:21 [
                    "id" => 6173
                    "created_at" => "2026-04-10 13:58:26"
                    "updated_at" => null
                    "title" => "Условие"
                    "field_order" => "1"
                    "field_publisher" => Illuminate\Database\Eloquent\Collection {#1102
                      #items: array:1 [ …1]
                      #escapeWhenCastingToString: false
                    }
                    "field_content_type" => "free"
                    "field_content_mode" => "text, image"
                    "field_page_content_mode" => "image"
                    "field_content_text_checked" => null
                    "field_page_content_text_checked" => "0"
                    "field_solution_author" => "Автор"
                    "field_moderator" => "stas"
                    "field_edition_type" => "statement"
                    "field_root_dir" => "0-"
                    "field_responsible" => Illuminate\Database\Eloquent\Collection {#1103
                      #items: []
                      #escapeWhenCastingToString: false
                    }
                    "field_comment" => null
                    "field_similar_book" => Illuminate\Database\Eloquent\Collection {#1101
                      #items: []
                      #escapeWhenCastingToString: false
                    }
                    "field_process_formula" => "katex"
                    "field_edition_group" => Illuminate\Database\Eloquent\Collection {#1100
                      #items: []
                      #escapeWhenCastingToString: false
                    }
                    "field_content_source" => null
                  ]
                  #original: array:21 [
                    "id" => 6173
                    "created_at" => "2026-04-10 13:58:26"
                    "updated_at" => null
                    "title" => "Условие"
                    "field_order" => "1"
                    "field_publisher" => Illuminate\Database\Eloquent\Collection {#1102}
                    "field_content_type" => "free"
                    "field_content_mode" => "text, image"
                    "field_page_content_mode" => "image"
                    "field_content_text_checked" => null
                    "field_page_content_text_checked" => "0"
                    "field_solution_author" => "Автор"
                    "field_moderator" => "stas"
                    "field_edition_type" => "statement"
                    "field_root_dir" => "0-"
                    "field_responsible" => Illuminate\Database\Eloquent\Collection {#1103}
                    "field_comment" => null
                    "field_similar_book" => Illuminate\Database\Eloquent\Collection {#1101}
                    "field_process_formula" => "katex"
                    "field_edition_group" => Illuminate\Database\Eloquent\Collection {#1100}
                    "field_content_source" => null
                  ]
                  #changes: []
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                  #attributeCastCache: []
                  #dateFormat: null
                  #appends: []
                  #dispatchesEvents: []
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                  #touches: []
                  +timestamps: true
                  +usesUniqueIds: false
                  #hidden: []
                  #visible: []
                  #fillable: []
                  #guarded: array:1 [
                    0 => "*"
                  ]
                }
              ]
              #escapeWhenCastingToString: false
            }
            "task" => array:2 [
              "refs" => "1435123"
              "type" => "task"
            ]
            "text" => "<p><strong>11.</strong> По наклонной доске, образующей с горизонтом угол $\alpha = 30^\circ$, рабочий равномерно двигает вверх ящик. Прикладываемая им сила направлена параллельно доске. Коэффициент трения ящика о доску равен $\mu = 0,1$. Определите, во сколько раз прикладываемая рабочим сила меньше силы тяжести, действующей на ящик. Рассчитайте КПД этого простого механизма.</p><p><strong>Решение.</strong></p>"
            "img" => array:1 [
              0 => array:5 [
                "name" => "11-1.jpg"
                "alt" => null
                "width" => "1998"
                "height" => 500
                "path" => "/media/fizika_09/grachev-rt/0-30/11-1.webp?ts=1759402767"
              ]
            ]
          ]
          #original: array:7 [
            "id" => 1698511
            "created_at" => "2026-04-10 13:58:26"
            "updated_at" => null
            "edition" => Illuminate\Database\Eloquent\Collection {#1098}
            "task" => array:2 [
              "refs" => "1435123"
              "type" => "task"
            ]
            "text" => "<p><strong>11.</strong> По наклонной доске, образующей с горизонтом угол $\alpha = 30^\circ$, рабочий равномерно двигает вверх ящик. Прикладываемая им сила направлена параллельно доске. Коэффициент трения ящика о доску равен $\mu = 0,1$. Определите, во сколько раз прикладываемая рабочим сила меньше силы тяжести, действующей на ящик. Рассчитайте КПД этого простого механизма.</p><p><strong>Решение.</strong></p>"
            "img" => array:1 [
              0 => array:5 [
                "name" => "11-1.jpg"
                "alt" => null
                "width" => "1998"
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            "text" => "<p><strong>Дано:</strong></p> <p>Угол наклона доски: $\alpha = 30^{\circ}$</p> <p>Коэффициент трения: $\mu = 0,1$</p> <p>Движение: равномерное ($v = \text{const}$, $a = 0$)</p> <p><strong>Найти:</strong></p> <p>1. Отношение силы тяжести к прикладываемой силе: $\frac{F_{тяж}}{F_{пр}}$</p> <p>2. КПД механизма: $\eta$</p> <p><strong>Решение:</strong></p> <p>На ящик, движущийся равномерно вверх по наклонной плоскости, действуют четыре силы: сила тяжести ($\vec{F}_{тяж}$), сила нормальной реакции опоры ($\vec{N}$), прикладываемая сила ($\vec{F}_{пр}$) и сила трения скольжения ($\vec{F}_{тр}$).</p> <p>Выберем систему координат, в которой ось $Ox$ направлена вдоль наклонной плоскости вверх, а ось $Oy$ — перпендикулярно ей.</p> <p>Поскольку движение равномерное, ускорение ящика равно нулю. Согласно второму закону Ньютона, векторная сумма всех действующих на тело сил равна нулю:</p> <p>$\vec{F}_{пр} + \vec{F}_{тяж} + \vec{N} + \vec{F}_{тр} = 0$</p> <p>Спроецируем это уравнение на оси координат. Сила тяжести $F_{тяж} = mg$. Ее проекции: на ось $Ox$ равна $-mg \sin(\alpha)$, на ось $Oy$ равна $-mg \cos(\alpha)$.</p> <p>В проекции на ось $Oy$:</p> <p>$N - mg \cos(\alpha) = 0 \implies N = mg \cos(\alpha)$</p> <p>В проекции на ось $Ox$:</p> <p>$F_{пр} - mg \sin(\alpha) - F_{тр} = 0$</p> <p>Сила трения скольжения связана с силой нормальной реакции опоры соотношением $F_{тр} = \mu N$. Подставив выражение для $N$, получаем:</p> <p>$F_{тр} = \mu mg \cos(\alpha)$</p> <p>Теперь подставим силу трения в уравнение для оси $Ox$ и выразим прикладываемую силу $F_{пр}$:</p> <p>$F_{пр} = mg \sin(\alpha) + F_{тр} = mg \sin(\alpha) + \mu mg \cos(\alpha) = mg(\sin(\alpha) + \mu \cos(\alpha))$</p> <p><strong>1. Определение, во сколько раз прикладываемая сила меньше силы тяжести</strong></p> <p>Для ответа на этот вопрос необходимо найти отношение силы тяжести $F_{тяж}$ к прикладываемой силе $F_{пр}$.</p> <p>$\frac{F_{тяж}}{F_{пр}} = \frac{mg}{mg(\sin(\alpha) + \mu \cos(\alpha))} = \frac{1}{\sin(\alpha) + \mu \cos(\alpha)}$</p> <p>Подставим числовые значения $\alpha = 30^{\circ}$ и $\mu = 0,1$:</p> <p>$\sin(30^{\circ}) = 0,5$</p> <p>$\cos(30^{\circ}) = \frac{\sqrt{3}}{2} \approx 0,866$</p> <p>$\frac{F_{тяж}}{F_{пр}} = \frac{1}{0,5 + 0,1 \cdot 0,866} = \frac{1}{0,5 + 0,0866} = \frac{1}{0,5866} \approx 1,705$</p> <p><strong>Ответ:</strong> Прикладываемая рабочим сила меньше силы тяжести примерно в 1,7 раза.</p> <p><strong>2. Расчет КПД этого простого механизма</strong></p> <p>Коэффициент полезного действия (КПД) наклонной плоскости как механизма определяется отношением полезной работы ($A_{полезная}$) к затраченной работе ($A_{затраченная}$): $\eta = \frac{A_{полезная}}{A_{затраченная}}$.</p> <p>Пусть ящик перемещается на расстояние $L$ вдоль наклонной плоскости. </p> <p>Полезная работа — это работа по подъему ящика на высоту $h = L \sin(\alpha)$ без учета трения. Она равна изменению потенциальной энергии: $A_{полезная} = mgh = mgL \sin(\alpha)$.</p> <p>Затраченная работа — это работа, совершаемая прикладываемой силой $F_{пр}$ для перемещения ящика на расстояние $L$: $A_{затраченная} = F_{пр} \cdot L$.</p> <p>Используя найденное ранее выражение для $F_{пр}$, получаем:</p> <p>$A_{затраченная} = mg(\sin(\alpha) + \mu \cos(\alpha)) \cdot L$</p> <p>Теперь можно рассчитать КПД:</p> <p>$\eta = \frac{A_{полезная}}{A_{затраченная}} = \frac{mgL \sin(\alpha)}{mgL(\sin(\alpha) + \mu \cos(\alpha))} = \frac{\sin(\alpha)}{\sin(\alpha) + \mu \cos(\alpha)}$</p> <p>Подставляя числовые значения, получаем:</p> <p>$\eta = \frac{0,5}{0,5 + 0,1 \cdot 0,866} = \frac{0,5}{0,5866} \approx 0,852$</p> <p>Для выражения КПД в процентах, умножим результат на 100%:</p> <p>$\eta \approx 0,852 \cdot 100\% = 85,2\%$</p> <p><strong>Ответ:</strong> КПД этого простого механизма составляет примерно 85,2%.</p>"
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            "text" => "<p><strong>Дано:</strong></p> <p>Угол наклона доски: $\alpha = 30^{\circ}$</p> <p>Коэффициент трения: $\mu = 0,1$</p> <p>Движение: равномерное ($v = \text{const}$, $a = 0$)</p> <p><strong>Найти:</strong></p> <p>1. Отношение силы тяжести к прикладываемой силе: $\frac{F_{тяж}}{F_{пр}}$</p> <p>2. КПД механизма: $\eta$</p> <p><strong>Решение:</strong></p> <p>На ящик, движущийся равномерно вверх по наклонной плоскости, действуют четыре силы: сила тяжести ($\vec{F}_{тяж}$), сила нормальной реакции опоры ($\vec{N}$), прикладываемая сила ($\vec{F}_{пр}$) и сила трения скольжения ($\vec{F}_{тр}$).</p> <p>Выберем систему координат, в которой ось $Ox$ направлена вдоль наклонной плоскости вверх, а ось $Oy$ — перпендикулярно ей.</p> <p>Поскольку движение равномерное, ускорение ящика равно нулю. Согласно второму закону Ньютона, векторная сумма всех действующих на тело сил равна нулю:</p> <p>$\vec{F}_{пр} + \vec{F}_{тяж} + \vec{N} + \vec{F}_{тр} = 0$</p> <p>Спроецируем это уравнение на оси координат. Сила тяжести $F_{тяж} = mg$. Ее проекции: на ось $Ox$ равна $-mg \sin(\alpha)$, на ось $Oy$ равна $-mg \cos(\alpha)$.</p> <p>В проекции на ось $Oy$:</p> <p>$N - mg \cos(\alpha) = 0 \implies N = mg \cos(\alpha)$</p> <p>В проекции на ось $Ox$:</p> <p>$F_{пр} - mg \sin(\alpha) - F_{тр} = 0$</p> <p>Сила трения скольжения связана с силой нормальной реакции опоры соотношением $F_{тр} = \mu N$. Подставив выражение для $N$, получаем:</p> <p>$F_{тр} = \mu mg \cos(\alpha)$</p> <p>Теперь подставим силу трения в уравнение для оси $Ox$ и выразим прикладываемую силу $F_{пр}$:</p> <p>$F_{пр} = mg \sin(\alpha) + F_{тр} = mg \sin(\alpha) + \mu mg \cos(\alpha) = mg(\sin(\alpha) + \mu \cos(\alpha))$</p> <p><strong>1. Определение, во сколько раз прикладываемая сила меньше силы тяжести</strong></p> <p>Для ответа на этот вопрос необходимо найти отношение силы тяжести $F_{тяж}$ к прикладываемой силе $F_{пр}$.</p> <p>$\frac{F_{тяж}}{F_{пр}} = \frac{mg}{mg(\sin(\alpha) + \mu \cos(\alpha))} = \frac{1}{\sin(\alpha) + \mu \cos(\alpha)}$</p> <p>Подставим числовые значения $\alpha = 30^{\circ}$ и $\mu = 0,1$:</p> <p>$\sin(30^{\circ}) = 0,5$</p> <p>$\cos(30^{\circ}) = \frac{\sqrt{3}}{2} \approx 0,866$</p> <p>$\frac{F_{тяж}}{F_{пр}} = \frac{1}{0,5 + 0,1 \cdot 0,866} = \frac{1}{0,5 + 0,0866} = \frac{1}{0,5866} \approx 1,705$</p> <p><strong>Ответ:</strong> Прикладываемая рабочим сила меньше силы тяжести примерно в 1,7 раза.</p> <p><strong>2. Расчет КПД этого простого механизма</strong></p> <p>Коэффициент полезного действия (КПД) наклонной плоскости как механизма определяется отношением полезной работы ($A_{полезная}$) к затраченной работе ($A_{затраченная}$): $\eta = \frac{A_{полезная}}{A_{затраченная}}$.</p> <p>Пусть ящик перемещается на расстояние $L$ вдоль наклонной плоскости. </p> <p>Полезная работа — это работа по подъему ящика на высоту $h = L \sin(\alpha)$ без учета трения. Она равна изменению потенциальной энергии: $A_{полезная} = mgh = mgL \sin(\alpha)$.</p> <p>Затраченная работа — это работа, совершаемая прикладываемой силой $F_{пр}$ для перемещения ящика на расстояние $L$: $A_{затраченная} = F_{пр} \cdot L$.</p> <p>Используя найденное ранее выражение для $F_{пр}$, получаем:</p> <p>$A_{затраченная} = mg(\sin(\alpha) + \mu \cos(\alpha)) \cdot L$</p> <p>Теперь можно рассчитать КПД:</p> <p>$\eta = \frac{A_{полезная}}{A_{затраченная}} = \frac{mgL \sin(\alpha)}{mgL(\sin(\alpha) + \mu \cos(\alpha))} = \frac{\sin(\alpha)}{\sin(\alpha) + \mu \cos(\alpha)}$</p> <p>Подставляя числовые значения, получаем:</p> <p>$\eta = \frac{0,5}{0,5 + 0,1 \cdot 0,866} = \frac{0,5}{0,5866} \approx 0,852$</p> <p>Для выражения КПД в процентах, умножим результат на 100%:</p> <p>$\eta \approx 0,852 \cdot 100\% = 85,2\%$</p> <p><strong>Ответ:</strong> КПД этого простого механизма составляет примерно 85,2%.</p>"
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№11 (с. 45)
Условие. №11 (с. 45)
скриншот условия
Физика, 9 класс рабочая тетрадь, авторы: Грачев Александр Васильевич, Погожев Владимир Александрович, Боков Павел Юрьевич, Вишнякова Екатерина Анатольевна, издательство Просвещение, Москва, 2021, Часть 2, страница 45, номер 11, Условие

11. По наклонной доске, образующей с горизонтом угол $\alpha = 30^\circ$, рабочий равномерно двигает вверх ящик. Прикладываемая им сила направлена параллельно доске. Коэффициент трения ящика о доску равен $\mu = 0,1$. Определите, во сколько раз прикладываемая рабочим сила меньше силы тяжести, действующей на ящик. Рассчитайте КПД этого простого механизма.

Решение.

Решение. №11 (с. 45)

Дано:

Угол наклона доски: $\alpha = 30^{\circ}$

Коэффициент трения: $\mu = 0,1$

Движение: равномерное ($v = \text{const}$, $a = 0$)

Найти:

1. Отношение силы тяжести к прикладываемой силе: $\frac{F_{тяж}}{F_{пр}}$

2. КПД механизма: $\eta$

Решение:

На ящик, движущийся равномерно вверх по наклонной плоскости, действуют четыре силы: сила тяжести ($\vec{F}_{тяж}$), сила нормальной реакции опоры ($\vec{N}$), прикладываемая сила ($\vec{F}_{пр}$) и сила трения скольжения ($\vec{F}_{тр}$).

Выберем систему координат, в которой ось $Ox$ направлена вдоль наклонной плоскости вверх, а ось $Oy$ — перпендикулярно ей.

Поскольку движение равномерное, ускорение ящика равно нулю. Согласно второму закону Ньютона, векторная сумма всех действующих на тело сил равна нулю:

$\vec{F}_{пр} + \vec{F}_{тяж} + \vec{N} + \vec{F}_{тр} = 0$

Спроецируем это уравнение на оси координат. Сила тяжести $F_{тяж} = mg$. Ее проекции: на ось $Ox$ равна $-mg \sin(\alpha)$, на ось $Oy$ равна $-mg \cos(\alpha)$.

В проекции на ось $Oy$:

$N - mg \cos(\alpha) = 0 \implies N = mg \cos(\alpha)$

В проекции на ось $Ox$:

$F_{пр} - mg \sin(\alpha) - F_{тр} = 0$

Сила трения скольжения связана с силой нормальной реакции опоры соотношением $F_{тр} = \mu N$. Подставив выражение для $N$, получаем:

$F_{тр} = \mu mg \cos(\alpha)$

Теперь подставим силу трения в уравнение для оси $Ox$ и выразим прикладываемую силу $F_{пр}$:

$F_{пр} = mg \sin(\alpha) + F_{тр} = mg \sin(\alpha) + \mu mg \cos(\alpha) = mg(\sin(\alpha) + \mu \cos(\alpha))$

1. Определение, во сколько раз прикладываемая сила меньше силы тяжести

Для ответа на этот вопрос необходимо найти отношение силы тяжести $F_{тяж}$ к прикладываемой силе $F_{пр}$.

$\frac{F_{тяж}}{F_{пр}} = \frac{mg}{mg(\sin(\alpha) + \mu \cos(\alpha))} = \frac{1}{\sin(\alpha) + \mu \cos(\alpha)}$

Подставим числовые значения $\alpha = 30^{\circ}$ и $\mu = 0,1$:

$\sin(30^{\circ}) = 0,5$

$\cos(30^{\circ}) = \frac{\sqrt{3}}{2} \approx 0,866$

$\frac{F_{тяж}}{F_{пр}} = \frac{1}{0,5 + 0,1 \cdot 0,866} = \frac{1}{0,5 + 0,0866} = \frac{1}{0,5866} \approx 1,705$

Ответ: Прикладываемая рабочим сила меньше силы тяжести примерно в 1,7 раза.

2. Расчет КПД этого простого механизма

Коэффициент полезного действия (КПД) наклонной плоскости как механизма определяется отношением полезной работы ($A_{полезная}$) к затраченной работе ($A_{затраченная}$): $\eta = \frac{A_{полезная}}{A_{затраченная}}$.

Пусть ящик перемещается на расстояние $L$ вдоль наклонной плоскости.

Полезная работа — это работа по подъему ящика на высоту $h = L \sin(\alpha)$ без учета трения. Она равна изменению потенциальной энергии: $A_{полезная} = mgh = mgL \sin(\alpha)$.

Затраченная работа — это работа, совершаемая прикладываемой силой $F_{пр}$ для перемещения ящика на расстояние $L$: $A_{затраченная} = F_{пр} \cdot L$.

Используя найденное ранее выражение для $F_{пр}$, получаем:

$A_{затраченная} = mg(\sin(\alpha) + \mu \cos(\alpha)) \cdot L$

Теперь можно рассчитать КПД:

$\eta = \frac{A_{полезная}}{A_{затраченная}} = \frac{mgL \sin(\alpha)}{mgL(\sin(\alpha) + \mu \cos(\alpha))} = \frac{\sin(\alpha)}{\sin(\alpha) + \mu \cos(\alpha)}$

Подставляя числовые значения, получаем:

$\eta = \frac{0,5}{0,5 + 0,1 \cdot 0,866} = \frac{0,5}{0,5866} \approx 0,852$

Для выражения КПД в процентах, умножим результат на 100%:

$\eta \approx 0,852 \cdot 100\% = 85,2\%$

Ответ: КПД этого простого механизма составляет примерно 85,2%.

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