Номер 4, страница 184 - гдз по физике 10 класс учебник Касьянов

Физика, 10 класс Учебник, автор: Касьянов Валерий Алексеевич, издательство Просвещение, Москва, 2021, белого цвета

Авторы: Касьянов В. А.

Тип: Учебник

Издательство: Просвещение

Год издания: 2021 - 2026

Уровень обучения: углублённый

Цвет обложки: белый самолет и молнии изображены

ISBN: 978-5-09-103621-3

Механика. 6. Статика. Параграф 39. Условие равновесия для поступательного движения. Задачи - номер 4, страница 184.

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                            "field_cases" => array:6 [
                              "field_accusative_case" => "десятый"
                              "field_creative_case" => "десятым"
                              "field_dative_case" => "десятому"
                              "field_genitive_case" => "десятого"
                              "field_nominative_case" => "десятый"
                              "field_prepositional_case" => "десятом"
                            ]
                            "field_translit" => "desjatyj"
                          ]
                          #changes: []
                          #casts: []
                          #classCastCache: []
                          #attributeCastCache: []
                          #dateFormat: null
                          #appends: []
                          #dispatchesEvents: []
                          #observables: []
                          #relations: []
                          #touches: []
                          +timestamps: true
                          +usesUniqueIds: false
                          #hidden: []
                          #visible: []
                          #fillable: []
                          #guarded: array:1 [
                            0 => "*"
                          ]
                        }
                      ]
                      #escapeWhenCastingToString: false
                    }
                    "field_publisher" => Illuminate\Database\Eloquent\Collection {#1125
                      #items: array:1 [
                        0 => App\Models\Term {#1126
                          #connection: "mysql"
                          #table: "terms"
                          #primaryKey: "id"
                          #keyType: "int"
                          +incrementing: false
                          #with: []
                          #withCount: []
                          +preventsLazyLoading: false
                          #perPage: 15
                          +exists: true
                          +wasRecentlyCreated: false
                          #escapeWhenCastingToString: false
                          #attributes: array:6 [
                            "id" => 5153
                            "created_at" => "2026-04-10 13:58:26"
                            "updated_at" => null
                            "name" => "Просвещение"
                            "field_cases" => null
                            "field_translit" => "prosveschenie"
                          ]
                          #original: array:6 [
                            "id" => 5153
                            "created_at" => "2026-04-10 13:58:26"
                            "updated_at" => null
                            "name" => "Просвещение"
                            "field_cases" => null
                            "field_translit" => "prosveschenie"
                          ]
                          #changes: []
                          #casts: []
                          #classCastCache: []
                          #attributeCastCache: []
                          #dateFormat: null
                          #appends: []
                          #dispatchesEvents: []
                          #observables: []
                          #relations: []
                          #touches: []
                          +timestamps: true
                          +usesUniqueIds: false
                          #hidden: []
                          #visible: []
                          #fillable: []
                          #guarded: array:1 [
                            0 => "*"
                          ]
                        }
                      ]
                      #escapeWhenCastingToString: false
                    }
                    "field_author" => Illuminate\Database\Eloquent\Collection {#1127
                      #items: array:1 [
                        0 => App\Models\Term {#1128
                          #connection: "mysql"
                          #table: "terms"
                          #primaryKey: "id"
                          #keyType: "int"
                          +incrementing: false
                          #with: []
                          #withCount: []
                          +preventsLazyLoading: false
                          #perPage: 15
                          +exists: true
                          +wasRecentlyCreated: false
                          #escapeWhenCastingToString: false
                          #attributes: array:12 [
                            "id" => 4566
                            "created_at" => "2026-04-10 13:58:26"
                            "updated_at" => null
                            "name" => "Касьянов"
                            "field_bio" => null
                            "field_degree_rp" => null
                            "field_foreign_lang_name" => null
                            "field_foreign_lang_patronymic" => null
                            "field_foreign_lang_surname" => null
                            "field_name" => "Валерий"
                            "field_patronymic" => "Алексеевич"
                            "field_surname_rp" => null
                          ]
                          #original: array:12 [
                            "id" => 4566
                            "created_at" => "2026-04-10 13:58:26"
                            "updated_at" => null
                            "name" => "Касьянов"
                            "field_bio" => null
                            "field_degree_rp" => null
                            "field_foreign_lang_name" => null
                            "field_foreign_lang_patronymic" => null
                            "field_foreign_lang_surname" => null
                            "field_name" => "Валерий"
                            "field_patronymic" => "Алексеевич"
                            "field_surname_rp" => null
                          ]
                          #changes: []
                          #casts: []
                          #classCastCache: []
                          #attributeCastCache: []
                          #dateFormat: null
                          #appends: []
                          #dispatchesEvents: []
                          #observables: []
                          #relations: []
                          #touches: []
                          +timestamps: true
                          +usesUniqueIds: false
                          #hidden: []
                          #visible: []
                          #fillable: []
                          #guarded: array:1 [
                            0 => "*"
                          ]
                        }
                      ]
                      #escapeWhenCastingToString: false
                    }
                    "field_author_foreign" => Illuminate\Database\Eloquent\Collection {#1129
                      #items: []
                      #escapeWhenCastingToString: false
                    }
                    "field_book_type" => Illuminate\Database\Eloquent\Collection {#1130
                      #items: array:1 [
                        0 => App\Models\Term {#1131
                          #connection: "mysql"
                          #table: "terms"
                          #primaryKey: "id"
                          #keyType: "int"
                          +incrementing: false
                          #with: []
                          #withCount: []
                          +preventsLazyLoading: false
                          #perPage: 15
                          +exists: true
                          +wasRecentlyCreated: false
                          #escapeWhenCastingToString: false
                          #attributes: array:10 [
                            "id" => 6671
                            "created_at" => "2026-04-10 13:58:26"
                            "updated_at" => null
                            "name" => "Учебник"
                            "field_book_type_foreign" => null
                            "field_cases" => array:6 [
                              "field_accusative_case" => "учебник"
                              "field_creative_case" => "учебником"
                              "field_dative_case" => "учебнику"
                              "field_genitive_case" => "учебника"
                              "field_nominative_case" => "учебник"
                              "field_prepositional_case" => "учебнике"
                            ]
                            "field_plural_form" => null
                            "field_short_name" => null
                            "field_short_name_foreign" => null
                            "field_translit" => "uchebnik"
                          ]
                          #original: array:10 [
                            "id" => 6671
                            "created_at" => "2026-04-10 13:58:26"
                            "updated_at" => null
                            "name" => "Учебник"
                            "field_book_type_foreign" => null
                            "field_cases" => array:6 [
                              "field_accusative_case" => "учебник"
                              "field_creative_case" => "учебником"
                              "field_dative_case" => "учебнику"
                              "field_genitive_case" => "учебника"
                              "field_nominative_case" => "учебник"
                              "field_prepositional_case" => "учебнике"
                            ]
                            "field_plural_form" => null
                            "field_short_name" => null
                            "field_short_name_foreign" => null
                            "field_translit" => "uchebnik"
                          ]
                          #changes: []
                          #casts: []
                          #classCastCache: []
                          #attributeCastCache: []
                          #dateFormat: null
                          #appends: []
                          #dispatchesEvents: []
                          #observables: []
                          #relations: []
                          #touches: []
                          +timestamps: true
                          +usesUniqueIds: false
                          #hidden: []
                          #visible: []
                          #fillable: []
                          #guarded: array:1 [
                            0 => "*"
                          ]
                        }
                      ]
                      #escapeWhenCastingToString: false
                    }
                    "field_country" => Illuminate\Database\Eloquent\Collection {#1132
                      #items: array:1 [
                        0 => App\Models\Term {#1133
                          #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 {#1134
                      #items: array:1 [
                        0 => App\Models\Term {#1135
                          #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 {#1136
                      #items: []
                      #escapeWhenCastingToString: false
                    }
                    "field_umk" => Illuminate\Database\Eloquent\Collection {#1137
                      #items: []
                      #escapeWhenCastingToString: false
                    }
                    "field_level_of_education" => Illuminate\Database\Eloquent\Collection {#1138
                      #items: array:1 [
                        0 => App\Models\Term {#1139
                          #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" => 39
                            "created_at" => "2026-04-10 13:58:26"
                            "updated_at" => null
                            "name" => "углублённый"
                            "field_cases" => array:6 [
                              "field_accusative_case" => "углубленный"
                              "field_creative_case" => "углубленным"
                              "field_dative_case" => "углубленному"
                              "field_genitive_case" => "углубленного"
                              "field_nominative_case" => "углубленный"
                              "field_prepositional_case" => "углубленном"
                            ]
                            "field_translit" => "uglublennyy"
                          ]
                          #original: array:6 [
                            "id" => 39
                            "created_at" => "2026-04-10 13:58:26"
                            "updated_at" => null
                            "name" => "углублённый"
                            "field_cases" => array:6 [
                              "field_accusative_case" => "углубленный"
                              "field_creative_case" => "углубленным"
                              "field_dative_case" => "углубленному"
                              "field_genitive_case" => "углубленного"
                              "field_nominative_case" => "углубленный"
                              "field_prepositional_case" => "углубленном"
                            ]
                            "field_translit" => "uglublennyy"
                          ]
                          #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 {#1140
                      #items: array:1 [
                        0 => App\Models\Term {#1141
                          #connection: "mysql"
                          #table: "terms"
                          #primaryKey: "id"
                          #keyType: "int"
                          +incrementing: false
                          #with: []
                          #withCount: []
                          +preventsLazyLoading: false
                          #perPage: 15
                          +exists: true
                          +wasRecentlyCreated: false
                          #escapeWhenCastingToString: false
                          #attributes: array:10 [
                            "id" => 6706
                            "created_at" => "2026-04-10 13:58:26"
                            "updated_at" => null
                            "name" => "ФГОС (старый)"
                            "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_color" => null
                            "field_end_year" => "2022"
                            "field_start_year" => "2019"
                            "field_translit" => "fgos-old"
                            "field_type" => null
                          ]
                          #original: array:10 [
                            "id" => 6706
                            "created_at" => "2026-04-10 13:58:26"
                            "updated_at" => null
                            "name" => "ФГОС (старый)"
                            "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_color" => null
                            "field_end_year" => "2022"
                            "field_start_year" => "2019"
                            "field_translit" => "fgos-old"
                            "field_type" => null
                          ]
                          #changes: []
                          #casts: []
                          #classCastCache: []
                          #attributeCastCache: []
                          #dateFormat: null
                          #appends: []
                          #dispatchesEvents: []
                          #observables: []
                          #relations: []
                          #touches: []
                          +timestamps: true
                          +usesUniqueIds: false
                          #hidden: []
                          #visible: []
                          #fillable: []
                          #guarded: array:1 [
                            0 => "*"
                          ]
                        }
                      ]
                      #escapeWhenCastingToString: false
                    }
                    "field_publication_number" => "11"
                    "field_publication_type" => Illuminate\Database\Eloquent\Collection {#1142
                      #items: array:1 [
                        0 => App\Models\Term {#1143
                          #connection: "mysql"
                          #table: "terms"
                          #primaryKey: "id"
                          #keyType: "int"
                          +incrementing: false
                          #with: []
                          #withCount: []
                          +preventsLazyLoading: false
                          #perPage: 15
                          +exists: true
                          +wasRecentlyCreated: false
                          #escapeWhenCastingToString: false
                          #attributes: array:6 [
                            "id" => 33
                            "created_at" => "2026-04-10 13:58:26"
                            "updated_at" => null
                            "name" => "стереотипное"
                            "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" => "stereotipnoe"
                          ]
                          #original: array:6 [
                            "id" => 33
                            "created_at" => "2026-04-10 13:58:26"
                            "updated_at" => null
                            "name" => "стереотипное"
                            "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" => "stereotipnoe"
                          ]
                          #changes: []
                          #casts: []
                          #classCastCache: []
                          #attributeCastCache: []
                          #dateFormat: null
                          #appends: []
                          #dispatchesEvents: []
                          #observables: []
                          #relations: []
                          #touches: []
                          +timestamps: true
                          +usesUniqueIds: false
                          #hidden: []
                          #visible: []
                          #fillable: []
                          #guarded: array:1 [
                            0 => "*"
                          ]
                        }
                      ]
                      #escapeWhenCastingToString: false
                    }
                    "field_under_the_edition" => Illuminate\Database\Eloquent\Collection {#1144
                      #items: []
                      #escapeWhenCastingToString: false
                    }
                    "field_under_the_edition_degree" => null
                    "field_cover_description" => "самолет и молнии изображены"
                    "field_publication_year" => "2021"
                    "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" => "984"
                    "field_priority" => null
                    "field_default_folder" => "/fizika_10/kasyanov-u/"
                    "field_isbn" => "978-5-09-103621-3"
                    "field_cover" => array:1 [
                      0 => "/media/fizika_10/kasyanov-u/covers/cover1.webp?ts=1757588862"
                    ]
                    "field_cover_alts" => array:1 [
                      0 => ""
                    ]
                    "field_covers" => array:1 [
                      0 => array:4 [
                        "path" => "/media/fizika_10/kasyanov-u/covers/cover1.webp?ts=1757588862"
                        "alt" => ""
                        "width" => "1604"
                        "height" => "2397"
                      ]
                    ]
                    "field_popular_book" => "0"
                    "field_recommended_books" => Illuminate\Database\Eloquent\Collection {#1145
                      #items: []
                      #escapeWhenCastingToString: false
                    }
                    "field_new_book" => Illuminate\Database\Eloquent\Collection {#1146
                      #items: []
                      #escapeWhenCastingToString: false
                    }
                    "field_old_book" => Illuminate\Database\Eloquent\Collection {#1147
                      #items: []
                      #escapeWhenCastingToString: false
                    }
                    "field_url" => "/10-klass/fizika/kasyanov-uchebnik"
                    "field_cover_color" => Illuminate\Database\Eloquent\Collection {#1148
                      #items: array:1 [
                        0 => App\Models\Term {#1149
                          #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" => 45
                            "created_at" => "2026-04-10 13:58:26"
                            "updated_at" => null
                            "name" => "белый"
                            "field_cases" => array:6 [
                              "field_accusative_case" => "белый"
                              "field_creative_case" => "белым"
                              "field_dative_case" => "белому"
                              "field_genitive_case" => "белого"
                              "field_nominative_case" => "белый"
                              "field_prepositional_case" => "белом"
                            ]
                            "field_translit" => "belyy"
                          ]
                          #original: array:6 [
                            "id" => 45
                            "created_at" => "2026-04-10 13:58:26"
                            "updated_at" => null
                            "name" => "белый"
                            "field_cases" => array:6 [
                              "field_accusative_case" => "белый"
                              "field_creative_case" => "белым"
                              "field_dative_case" => "белому"
                              "field_genitive_case" => "белого"
                              "field_nominative_case" => "белый"
                              "field_prepositional_case" => "белом"
                            ]
                            "field_translit" => "belyy"
                          ]
                          #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" => 7000
                    "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 {#1122}
                    "field_class" => Illuminate\Database\Eloquent\Collection {#1123}
                    "field_publisher" => Illuminate\Database\Eloquent\Collection {#1125}
                    "field_author" => Illuminate\Database\Eloquent\Collection {#1127}
                    "field_author_foreign" => Illuminate\Database\Eloquent\Collection {#1129}
                    "field_book_type" => Illuminate\Database\Eloquent\Collection {#1130}
                    "field_country" => Illuminate\Database\Eloquent\Collection {#1132}
                    "field_city" => Illuminate\Database\Eloquent\Collection {#1134}
                    "field_series" => Illuminate\Database\Eloquent\Collection {#1136}
                    "field_umk" => Illuminate\Database\Eloquent\Collection {#1137}
                    "field_level_of_education" => Illuminate\Database\Eloquent\Collection {#1138}
                    "field_standart_of_education" => Illuminate\Database\Eloquent\Collection {#1140}
                    "field_publication_number" => "11"
                    "field_publication_type" => Illuminate\Database\Eloquent\Collection {#1142}
                    "field_under_the_edition" => Illuminate\Database\Eloquent\Collection {#1144}
                    "field_under_the_edition_degree" => null
                    "field_cover_description" => "самолет и молнии изображены"
                    "field_publication_year" => "2021"
                    "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" => "984"
                    "field_priority" => null
                    "field_default_folder" => "/fizika_10/kasyanov-u/"
                    "field_isbn" => "978-5-09-103621-3"
                    "field_cover" => array:1 [
                      0 => "/media/fizika_10/kasyanov-u/covers/cover1.webp?ts=1757588862"
                    ]
                    "field_cover_alts" => array:1 [
                      0 => ""
                    ]
                    "field_covers" => array:1 [
                      0 => array:4 [
                        "path" => "/media/fizika_10/kasyanov-u/covers/cover1.webp?ts=1757588862"
                        "alt" => ""
                        "width" => "1604"
                        "height" => "2397"
                      ]
                    ]
                    "field_popular_book" => "0"
                    "field_recommended_books" => Illuminate\Database\Eloquent\Collection {#1145}
                    "field_new_book" => Illuminate\Database\Eloquent\Collection {#1146}
                    "field_old_book" => Illuminate\Database\Eloquent\Collection {#1147}
                    "field_url" => "/10-klass/fizika/kasyanov-uchebnik"
                    "field_cover_color" => Illuminate\Database\Eloquent\Collection {#1148}
                    "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 {#1150
              #items: []
              #escapeWhenCastingToString: false
            }
          ]
          #original: array:24 [
            "id" => 1389404
            "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 {#1119}
            "field_page_start" => "18"
            "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 {#1152}
            "branch_parent" => Illuminate\Database\Eloquent\Collection {#1150}
          ]
          #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 {#1151
          #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" => 1389495
            "created_at" => "2026-04-10 13:58:26"
            "updated_at" => null
            "field_display_title" => "6. Статика"
            "field_branch_order" => null
            "field_url" => null
            "field_branch_type" => Illuminate\Database\Eloquent\Collection {#1153
              #items: []
              #escapeWhenCastingToString: false
            }
            "field_page_start" => "179"
            "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 {#1154
              #items: array:1 [
                0 => App\Models\Book {#1120}
              ]
              #escapeWhenCastingToString: false
            }
            "branch_parent" => Illuminate\Database\Eloquent\Collection {#1155
              #items: array:1 [
                0 => App\Models\Branch {#1034}
              ]
              #escapeWhenCastingToString: false
            }
          ]
          #original: array:24 [
            "id" => 1389495
            "created_at" => "2026-04-10 13:58:26"
            "updated_at" => null
            "field_display_title" => "6. Статика"
            "field_branch_order" => null
            "field_url" => null
            "field_branch_type" => Illuminate\Database\Eloquent\Collection {#1153}
            "field_page_start" => "179"
            "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 {#1154}
            "branch_parent" => Illuminate\Database\Eloquent\Collection {#1155}
          ]
          #changes: []
          #casts: []
          #classCastCache: []
          #attributeCastCache: []
          #dateFormat: null
          #appends: []
          #dispatchesEvents: []
          #observables: []
          #relations: []
          #touches: []
          +timestamps: true
          +usesUniqueIds: false
          #hidden: []
          #visible: []
          #fillable: []
          #guarded: array:1 [
            0 => "*"
          ]
        }
        2 => App\Models\Branch {#1156
          #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" => 1389496
            "created_at" => "2026-04-10 13:58:26"
            "updated_at" => null
            "field_display_title" => "Условие равновесия для поступательного движения"
            "field_branch_order" => "39"
            "field_url" => null
            "field_branch_type" => Illuminate\Database\Eloquent\Collection {#1160
              #items: array:1 [
                0 => App\Models\Term {#1157
                  #connection: "mysql"
                  #table: "terms"
                  #primaryKey: "id"
                  #keyType: "int"
                  +incrementing: false
                  #with: []
                  #withCount: []
                  +preventsLazyLoading: false
                  #perPage: 15
                  +exists: true
                  +wasRecentlyCreated: false
                  #escapeWhenCastingToString: false
                  #attributes: array: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: []
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                  #classCastCache: []
                  #attributeCastCache: []
                  #dateFormat: null
                  #appends: []
                  #dispatchesEvents: []
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                  #relations: []
                  #touches: []
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                  +usesUniqueIds: false
                  #hidden: []
                  #visible: []
                  #fillable: []
                  #guarded: array:1 [
                    0 => "*"
                  ]
                }
              ]
              #escapeWhenCastingToString: false
            }
            "field_page_start" => "179"
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            "field_display_branch_page" => "1"
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            "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 {#1159
              #items: array:1 [
                0 => App\Models\Book {#1120}
              ]
              #escapeWhenCastingToString: false
            }
            "branch_parent" => Illuminate\Database\Eloquent\Collection {#1168
              #items: array:1 [
                0 => App\Models\Branch {#1167
                  #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" => 1389495
                    "created_at" => "2026-04-10 13:58:26"
                    "updated_at" => null
                    "field_display_title" => "6. Статика"
                    "field_branch_order" => null
                    "field_url" => null
                    "field_branch_type" => Illuminate\Database\Eloquent\Collection {#1169
                      #items: []
                      #escapeWhenCastingToString: false
                    }
                    "field_page_start" => "179"
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                    "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
                    "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 {#1170
                      #items: array:1 [
                        0 => App\Models\Book {#1120}
                      ]
                      #escapeWhenCastingToString: false
                    }
                    "branch_parent" => Illuminate\Database\Eloquent\Collection {#1171
                      #items: array:1 [
                        0 => App\Models\Branch {#1034}
                      ]
                      #escapeWhenCastingToString: false
                    }
                  ]
                  #original: array:24 [
                    "id" => 1389495
                    "created_at" => "2026-04-10 13:58:26"
                    "updated_at" => null
                    "field_display_title" => "6. Статика"
                    "field_branch_order" => null
                    "field_url" => null
                    "field_branch_type" => Illuminate\Database\Eloquent\Collection {#1169}
                    "field_page_start" => "179"
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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
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                    "field_description_bottom" => null
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                    "field_branch_covers" => []
                    "book" => Illuminate\Database\Eloquent\Collection {#1170}
                    "branch_parent" => Illuminate\Database\Eloquent\Collection {#1171}
                  ]
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                  #attributeCastCache: []
                  #dateFormat: null
                  #appends: []
                  #dispatchesEvents: []
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                  #relations: []
                  #touches: []
                  +timestamps: true
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                  #hidden: []
                  #visible: []
                  #fillable: []
                  #guarded: array:1 [
                    0 => "*"
                  ]
                }
              ]
              #escapeWhenCastingToString: false
            }
          ]
          #original: array:24 [
            "id" => 1389496
            "created_at" => "2026-04-10 13:58:26"
            "updated_at" => null
            "field_display_title" => "Условие равновесия для поступательного движения"
            "field_branch_order" => "39"
            "field_url" => null
            "field_branch_type" => Illuminate\Database\Eloquent\Collection {#1160}
            "field_page_start" => "179"
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            "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 {#1159}
            "branch_parent" => Illuminate\Database\Eloquent\Collection {#1168}
          ]
          #changes: []
          #casts: []
          #classCastCache: []
          #attributeCastCache: []
          #dateFormat: null
          #appends: []
          #dispatchesEvents: []
          #observables: []
          #relations: []
          #touches: []
          +timestamps: true
          +usesUniqueIds: false
          #hidden: []
          #visible: []
          #fillable: []
          #guarded: array:1 [
            0 => "*"
          ]
        }
        3 => App\Models\Branch {#1161
          #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" => 1389498
            "created_at" => "2026-04-10 13:58:26"
            "updated_at" => null
            "field_display_title" => "Задачи"
            "field_branch_order" => null
            "field_url" => null
            "field_branch_type" => Illuminate\Database\Eloquent\Collection {#1158
              #items: []
              #escapeWhenCastingToString: false
            }
            "field_page_start" => "183"
            "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 {#1164
              #items: array:1 [
                0 => App\Models\Book {#1120}
              ]
              #escapeWhenCastingToString: false
            }
            "branch_parent" => Illuminate\Database\Eloquent\Collection {#1177
              #items: array:1 [
                0 => App\Models\Branch {#1176
                  #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" => 1389496
                    "created_at" => "2026-04-10 13:58:26"
                    "updated_at" => null
                    "field_display_title" => "Условие равновесия для поступательного движения"
                    "field_branch_order" => "39"
                    "field_url" => null
                    "field_branch_type" => Illuminate\Database\Eloquent\Collection {#1178
                      #items: array:1 [
                        0 => App\Models\Term {#1157}
                      ]
                      #escapeWhenCastingToString: false
                    }
                    "field_page_start" => "179"
                    "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 {#1179
                      #items: array:1 [
                        0 => App\Models\Book {#1120}
                      ]
                      #escapeWhenCastingToString: false
                    }
                    "branch_parent" => Illuminate\Database\Eloquent\Collection {#1180
                      #items: array:1 [
                        0 => App\Models\Branch {#1167}
                      ]
                      #escapeWhenCastingToString: false
                    }
                  ]
                  #original: array:24 [
                    "id" => 1389496
                    "created_at" => "2026-04-10 13:58:26"
                    "updated_at" => null
                    "field_display_title" => "Условие равновесия для поступательного движения"
                    "field_branch_order" => "39"
                    "field_url" => null
                    "field_branch_type" => Illuminate\Database\Eloquent\Collection {#1178}
                    "field_page_start" => "179"
                    "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 {#1179}
                    "branch_parent" => Illuminate\Database\Eloquent\Collection {#1180}
                  ]
                  #changes: []
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                  #attributeCastCache: []
                  #dateFormat: null
                  #appends: []
                  #dispatchesEvents: []
                  #observables: []
                  #relations: []
                  #touches: []
                  +timestamps: true
                  +usesUniqueIds: false
                  #hidden: []
                  #visible: []
                  #fillable: []
                  #guarded: array:1 [
                    0 => "*"
                  ]
                }
              ]
              #escapeWhenCastingToString: false
            }
          ]
          #original: array:24 [
            "id" => 1389498
            "created_at" => "2026-04-10 13:58:26"
            "updated_at" => null
            "field_display_title" => "Задачи"
            "field_branch_order" => null
            "field_url" => null
            "field_branch_type" => Illuminate\Database\Eloquent\Collection {#1158}
            "field_page_start" => "183"
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                    "field_responsible" => Illuminate\Database\Eloquent\Collection {#1096
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            "text" => "<p><strong>4.</strong> Чемодан массой 30 кг скатывается с наклонной плоскости, составляющей угол $30^\circ$ с горизонтом. Коэффициент трения между поверхностью чемодана и плоскостью равен 0,3. С какой минимальной силой следует прижимать чемодан к плоскости, чтобы он скатывался с постоянной скоростью?</p>"
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            "edition" => Illuminate\Database\Eloquent\Collection {#1089}
            "task" => array:2 [
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            "text" => "<p><strong>4.</strong> Чемодан массой 30 кг скатывается с наклонной плоскости, составляющей угол $30^\circ$ с горизонтом. Коэффициент трения между поверхностью чемодана и плоскостью равен 0,3. С какой минимальной силой следует прижимать чемодан к плоскости, чтобы он скатывался с постоянной скоростью?</p>"
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            "text" => "<p><strong>Дано:</strong></p><p>$m = 30$ кг</p><p>$\alpha = 30°$</p><p>$\mu = 0.3$</p><p>$v = \text{const}$ (скорость постоянна, следовательно ускорение $a=0$)</p><p>$g \approx 10 \frac{\text{м}}{\text{с}^2}$ (ускорение свободного падения)</p><p><strong>Найти:</strong></p><p>$F$ - ?</p><p><strong>Решение:</strong></p><p>Поскольку чемодан скатывается с постоянной скоростью, его ускорение равно нулю. Согласно второму закону Ньютона, векторная сумма всех сил, действующих на чемодан, равна нулю: $\sum \vec{F} = 0$.</p><p>Выберем систему координат, в которой ось $Ox$ направлена вдоль наклонной плоскости вниз, а ось $Oy$ – перпендикулярно плоскости вверх. На чемодан действуют: сила тяжести $m\vec{g}$, сила нормальной реакции опоры $\vec{N}$, сила трения скольжения $\vec{F}_{тр}$ и минимальная прижимающая сила $\vec{F}$, которая по условию должна быть приложена к плоскости. Для того чтобы сила была минимальной, она должна быть направлена перпендикулярно плоскости, так как в этом случае она наиболее эффективно увеличивает силу нормальной реакции и, следовательно, силу трения.</p><p>Запишем второй закон Ньютона в проекциях на выбранные оси координат:</p><p>Проекция на ось $Oy$:</p><p>$N - mg \cos(\alpha) - F = 0$</p><p>Отсюда выразим силу нормальной реакции опоры $N$:</p><p>$N = mg \cos(\alpha) + F$</p><p>Проекция на ось $Ox$:</p><p>$mg \sin(\alpha) - F_{тр} = 0$</p><p>Из этого уравнения следует, что для равномерного движения сила трения должна уравновешивать скатывающую силу:</p><p>$F_{тр} = mg \sin(\alpha)$</p><p>Сила трения скольжения связана с силой нормальной реакции через коэффициент трения $\mu$:</p><p>$F_{тр} = \mu N$</p><p>Подставим в это уравнение выражение для $N$ из проекции на ось $Oy$:</p><p>$F_{тр} = \mu (mg \cos(\alpha) + F)$</p><p>Теперь приравняем два полученных выражения для силы трения:</p><p>$mg \sin(\alpha) = \mu (mg \cos(\alpha) + F)$</p><p>Из этого уравнения выразим искомую силу $F$:</p><p>$mg \sin(\alpha) = \mu mg \cos(\alpha) + \mu F$</p><p>$\mu F = mg \sin(\alpha) - \mu mg \cos(\alpha)$</p><p>$F = \frac{mg (\sin(\alpha) - \mu \cos(\alpha))}{\mu} = mg \left( \frac{\sin(\alpha)}{\mu} - \cos(\alpha) \right)$</p><p>Подставим числовые значения:</p><p>$F = 30 \cdot 10 \left( \frac{\sin(30°)}{0.3} - \cos(30°) \right) = 300 \left( \frac{0.5}{0.3} - \frac{\sqrt{3}}{2} \right)$</p><p>$F \approx 300 \left( 1.667 - 0.866 \right) = 300 \cdot 0.801 \approx 240.3$ Н.</p><p><strong>Ответ:</strong> $240.3$ Н.</p>"
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            "text" => "<p><strong>Дано:</strong></p><p>$m = 30$ кг</p><p>$\alpha = 30°$</p><p>$\mu = 0.3$</p><p>$v = \text{const}$ (скорость постоянна, следовательно ускорение $a=0$)</p><p>$g \approx 10 \frac{\text{м}}{\text{с}^2}$ (ускорение свободного падения)</p><p><strong>Найти:</strong></p><p>$F$ - ?</p><p><strong>Решение:</strong></p><p>Поскольку чемодан скатывается с постоянной скоростью, его ускорение равно нулю. Согласно второму закону Ньютона, векторная сумма всех сил, действующих на чемодан, равна нулю: $\sum \vec{F} = 0$.</p><p>Выберем систему координат, в которой ось $Ox$ направлена вдоль наклонной плоскости вниз, а ось $Oy$ – перпендикулярно плоскости вверх. На чемодан действуют: сила тяжести $m\vec{g}$, сила нормальной реакции опоры $\vec{N}$, сила трения скольжения $\vec{F}_{тр}$ и минимальная прижимающая сила $\vec{F}$, которая по условию должна быть приложена к плоскости. Для того чтобы сила была минимальной, она должна быть направлена перпендикулярно плоскости, так как в этом случае она наиболее эффективно увеличивает силу нормальной реакции и, следовательно, силу трения.</p><p>Запишем второй закон Ньютона в проекциях на выбранные оси координат:</p><p>Проекция на ось $Oy$:</p><p>$N - mg \cos(\alpha) - F = 0$</p><p>Отсюда выразим силу нормальной реакции опоры $N$:</p><p>$N = mg \cos(\alpha) + F$</p><p>Проекция на ось $Ox$:</p><p>$mg \sin(\alpha) - F_{тр} = 0$</p><p>Из этого уравнения следует, что для равномерного движения сила трения должна уравновешивать скатывающую силу:</p><p>$F_{тр} = mg \sin(\alpha)$</p><p>Сила трения скольжения связана с силой нормальной реакции через коэффициент трения $\mu$:</p><p>$F_{тр} = \mu N$</p><p>Подставим в это уравнение выражение для $N$ из проекции на ось $Oy$:</p><p>$F_{тр} = \mu (mg \cos(\alpha) + F)$</p><p>Теперь приравняем два полученных выражения для силы трения:</p><p>$mg \sin(\alpha) = \mu (mg \cos(\alpha) + F)$</p><p>Из этого уравнения выразим искомую силу $F$:</p><p>$mg \sin(\alpha) = \mu mg \cos(\alpha) + \mu F$</p><p>$\mu F = mg \sin(\alpha) - \mu mg \cos(\alpha)$</p><p>$F = \frac{mg (\sin(\alpha) - \mu \cos(\alpha))}{\mu} = mg \left( \frac{\sin(\alpha)}{\mu} - \cos(\alpha) \right)$</p><p>Подставим числовые значения:</p><p>$F = 30 \cdot 10 \left( \frac{\sin(30°)}{0.3} - \cos(30°) \right) = 300 \left( \frac{0.5}{0.3} - \frac{\sqrt{3}}{2} \right)$</p><p>$F \approx 300 \left( 1.667 - 0.866 \right) = 300 \cdot 0.801 \approx 240.3$ Н.</p><p><strong>Ответ:</strong> $240.3$ Н.</p>"
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№4 (с. 184)
Условие. №4 (с. 184)
скриншот условия
Физика, 10 класс Учебник, автор: Касьянов Валерий Алексеевич, издательство Просвещение, Москва, 2021, белого цвета, страница 184, номер 4, Условие

4. Чемодан массой 30 кг скатывается с наклонной плоскости, составляющей угол $30^\circ$ с горизонтом. Коэффициент трения между поверхностью чемодана и плоскостью равен 0,3. С какой минимальной силой следует прижимать чемодан к плоскости, чтобы он скатывался с постоянной скоростью?

Решение. №4 (с. 184)

Дано:

$m = 30$ кг

$\alpha = 30°$

$\mu = 0.3$

$v = \text{const}$ (скорость постоянна, следовательно ускорение $a=0$)

$g \approx 10 \frac{\text{м}}{\text{с}^2}$ (ускорение свободного падения)

Найти:

$F$ - ?

Решение:

Поскольку чемодан скатывается с постоянной скоростью, его ускорение равно нулю. Согласно второму закону Ньютона, векторная сумма всех сил, действующих на чемодан, равна нулю: $\sum \vec{F} = 0$.

Выберем систему координат, в которой ось $Ox$ направлена вдоль наклонной плоскости вниз, а ось $Oy$ – перпендикулярно плоскости вверх. На чемодан действуют: сила тяжести $m\vec{g}$, сила нормальной реакции опоры $\vec{N}$, сила трения скольжения $\vec{F}_{тр}$ и минимальная прижимающая сила $\vec{F}$, которая по условию должна быть приложена к плоскости. Для того чтобы сила была минимальной, она должна быть направлена перпендикулярно плоскости, так как в этом случае она наиболее эффективно увеличивает силу нормальной реакции и, следовательно, силу трения.

Запишем второй закон Ньютона в проекциях на выбранные оси координат:

Проекция на ось $Oy$:

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

Отсюда выразим силу нормальной реакции опоры $N$:

$N = mg \cos(\alpha) + F$

Проекция на ось $Ox$:

$mg \sin(\alpha) - F_{тр} = 0$

Из этого уравнения следует, что для равномерного движения сила трения должна уравновешивать скатывающую силу:

$F_{тр} = mg \sin(\alpha)$

Сила трения скольжения связана с силой нормальной реакции через коэффициент трения $\mu$:

$F_{тр} = \mu N$

Подставим в это уравнение выражение для $N$ из проекции на ось $Oy$:

$F_{тр} = \mu (mg \cos(\alpha) + F)$

Теперь приравняем два полученных выражения для силы трения:

$mg \sin(\alpha) = \mu (mg \cos(\alpha) + F)$

Из этого уравнения выразим искомую силу $F$:

$mg \sin(\alpha) = \mu mg \cos(\alpha) + \mu F$

$\mu F = mg \sin(\alpha) - \mu mg \cos(\alpha)$

$F = \frac{mg (\sin(\alpha) - \mu \cos(\alpha))}{\mu} = mg \left( \frac{\sin(\alpha)}{\mu} - \cos(\alpha) \right)$

Подставим числовые значения:

$F = 30 \cdot 10 \left( \frac{\sin(30°)}{0.3} - \cos(30°) \right) = 300 \left( \frac{0.5}{0.3} - \frac{\sqrt{3}}{2} \right)$

$F \approx 300 \left( 1.667 - 0.866 \right) = 300 \cdot 0.801 \approx 240.3$ Н.

Ответ: $240.3$ Н.

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