Номер 4, страница 376 - 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

Электростатика. 14. Силы электромагнитного взаимодействия неподвижных зарядов. Параграф 80. Равновесие статических зарядов. Задачи - номер 4, страница 376.

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                          #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 [ …6]
                            "field_plural_form" => null
                            "field_short_name" => null
                            "field_short_name_foreign" => null
                            "field_translit" => "uchebnik"
                          ]
                          #original: array:10 [
                            "id" => 6671
                            "created_at" => "2026-04-10 13:58:26"
                            "updated_at" => null
                            "name" => "Учебник"
                            "field_book_type_foreign" => null
                            "field_cases" => array:6 [ …6]
                            "field_plural_form" => null
                            "field_short_name" => null
                            "field_short_name_foreign" => null
                            "field_translit" => "uchebnik"
                          ]
                          #changes: []
                          #casts: []
                          #classCastCache: []
                          #attributeCastCache: []
                          #dateFormat: null
                          #appends: []
                          #dispatchesEvents: []
                          #observables: []
                          #relations: []
                          #touches: []
                          +timestamps: true
                          +usesUniqueIds: false
                          #hidden: []
                          #visible: []
                          #fillable: []
                          #guarded: array:1 [
                            0 => "*"
                          ]
                        }
                      ]
                      #escapeWhenCastingToString: false
                    }
                    "field_country" => Illuminate\Database\Eloquent\Collection {#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 [ …6]
                            "field_translit" => "rossiya"
                          ]
                          #original: array:6 [
                            "id" => 9
                            "created_at" => "2026-04-10 13:58:26"
                            "updated_at" => null
                            "name" => "Россия"
                            "field_cases" => array:6 [ …6]
                            "field_translit" => "rossiya"
                          ]
                          #changes: []
                          #casts: []
                          #classCastCache: []
                          #attributeCastCache: []
                          #dateFormat: null
                          #appends: []
                          #dispatchesEvents: []
                          #observables: []
                          #relations: []
                          #touches: []
                          +timestamps: true
                          +usesUniqueIds: false
                          #hidden: []
                          #visible: []
                          #fillable: []
                          #guarded: array:1 [
                            0 => "*"
                          ]
                        }
                      ]
                      #escapeWhenCastingToString: false
                    }
                    "field_city" => Illuminate\Database\Eloquent\Collection {#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 [ …6]
                            "field_translit" => "moskva"
                          ]
                          #original: array:6 [
                            "id" => 15
                            "created_at" => "2026-04-10 13:58:26"
                            "updated_at" => null
                            "name" => "Москва"
                            "field_cases" => array:6 [ …6]
                            "field_translit" => "moskva"
                          ]
                          #changes: []
                          #casts: []
                          #classCastCache: []
                          #attributeCastCache: []
                          #dateFormat: null
                          #appends: []
                          #dispatchesEvents: []
                          #observables: []
                          #relations: []
                          #touches: []
                          +timestamps: true
                          +usesUniqueIds: false
                          #hidden: []
                          #visible: []
                          #fillable: []
                          #guarded: array:1 [
                            0 => "*"
                          ]
                        }
                      ]
                      #escapeWhenCastingToString: false
                    }
                    "field_series" => Illuminate\Database\Eloquent\Collection {#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 [ …6]
                            "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 [ …6]
                            "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 [ …6]
                            "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 [ …6]
                            "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 [ …6]
                            "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 [ …6]
                            "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 [ …6]
                            "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 [ …6]
                            "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" => 1389608
            "created_at" => "2026-04-10 13:58:26"
            "updated_at" => null
            "field_display_title" => "Электростатика"
            "field_branch_order" => null
            "field_url" => null
            "field_branch_type" => Illuminate\Database\Eloquent\Collection {#1119}
            "field_page_start" => "362"
            "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" => 1389609
            "created_at" => "2026-04-10 13:58:26"
            "updated_at" => null
            "field_display_title" => "14. Силы электромагнитного взаимодействия неподвижных зарядов"
            "field_branch_order" => null
            "field_url" => null
            "field_branch_type" => Illuminate\Database\Eloquent\Collection {#1153
              #items: []
              #escapeWhenCastingToString: false
            }
            "field_page_start" => "362"
            "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" => 1389609
            "created_at" => "2026-04-10 13:58:26"
            "updated_at" => null
            "field_display_title" => "14. Силы электромагнитного взаимодействия неподвижных зарядов"
            "field_branch_order" => null
            "field_url" => null
            "field_branch_type" => Illuminate\Database\Eloquent\Collection {#1153}
            "field_page_start" => "362"
            "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: []
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          #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" => 1389617
            "created_at" => "2026-04-10 13:58:26"
            "updated_at" => null
            "field_display_title" => "Равновесие статических зарядов"
            "field_branch_order" => "80"
            "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
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                  #escapeWhenCastingToString: false
                  #attributes: array:7 [
                    "id" => 32
                    "created_at" => "2026-04-10 13:58:26"
                    "updated_at" => null
                    "name" => "Параграф"
                    "field_cases" => array:6 [ …6]
                    "field_page_check_not_needed" => null
                    "field_short_name" => "§"
                  ]
                  #original: array:7 [
                    "id" => 32
                    "created_at" => "2026-04-10 13:58:26"
                    "updated_at" => null
                    "name" => "Параграф"
                    "field_cases" => array:6 [ …6]
                    "field_page_check_not_needed" => null
                    "field_short_name" => "§"
                  ]
                  #changes: []
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                  #attributeCastCache: []
                  #dateFormat: null
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                  +timestamps: true
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                  #visible: []
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                    0 => "*"
                  ]
                }
              ]
              #escapeWhenCastingToString: false
            }
            "field_page_start" => "373"
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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" => 1389609
                    "created_at" => "2026-04-10 13:58:26"
                    "updated_at" => null
                    "field_display_title" => "14. Силы электромагнитного взаимодействия неподвижных зарядов"
                    "field_branch_order" => null
                    "field_url" => null
                    "field_branch_type" => Illuminate\Database\Eloquent\Collection {#1169 …2}
                    "field_page_start" => "362"
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                    "field_branch_expanded" => "0"
                    "field_display_branch_in_title" => "1"
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                    "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 {#1170 …2}
                    "branch_parent" => Illuminate\Database\Eloquent\Collection {#1171 …2}
                  ]
                  #original: array:24 [
                    "id" => 1389609
                    "created_at" => "2026-04-10 13:58:26"
                    "updated_at" => null
                    "field_display_title" => "14. Силы электромагнитного взаимодействия неподвижных зарядов"
                    "field_branch_order" => null
                    "field_url" => null
                    "field_branch_type" => Illuminate\Database\Eloquent\Collection {#1169 …2}
                    "field_page_start" => "362"
                    "field_branch_display" => "0"
                    "field_branch_expanded" => "0"
                    "field_display_branch_in_title" => "1"
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                    "field_h1" => null
                    "field_description_top" => null
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                    "field_branch_cover" => []
                    "field_branch_covers" => []
                    "book" => Illuminate\Database\Eloquent\Collection {#1170 …2}
                    "branch_parent" => Illuminate\Database\Eloquent\Collection {#1171 …2}
                  ]
                  #changes: []
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                  #attributeCastCache: []
                  #dateFormat: null
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                  #touches: []
                  +timestamps: true
                  +usesUniqueIds: false
                  #hidden: []
                  #visible: []
                  #fillable: []
                  #guarded: array:1 [
                    0 => "*"
                  ]
                }
              ]
              #escapeWhenCastingToString: false
            }
          ]
          #original: array:24 [
            "id" => 1389617
            "created_at" => "2026-04-10 13:58:26"
            "updated_at" => null
            "field_display_title" => "Равновесие статических зарядов"
            "field_branch_order" => "80"
            "field_url" => null
            "field_branch_type" => Illuminate\Database\Eloquent\Collection {#1160}
            "field_page_start" => "373"
            "field_branch_display" => "0"
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            "field_display_branch_in_title" => "1"
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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 {#1159}
            "branch_parent" => Illuminate\Database\Eloquent\Collection {#1168}
          ]
          #changes: []
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          #attributeCastCache: []
          #dateFormat: null
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          #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" => 1389619
            "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" => "376"
            "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" => 1389617
                    "created_at" => "2026-04-10 13:58:26"
                    "updated_at" => null
                    "field_display_title" => "Равновесие статических зарядов"
                    "field_branch_order" => "80"
                    "field_url" => null
                    "field_branch_type" => Illuminate\Database\Eloquent\Collection {#1178 …2}
                    "field_page_start" => "373"
                    "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 …2}
                    "branch_parent" => Illuminate\Database\Eloquent\Collection {#1180 …2}
                  ]
                  #original: array:24 [
                    "id" => 1389617
                    "created_at" => "2026-04-10 13:58:26"
                    "updated_at" => null
                    "field_display_title" => "Равновесие статических зарядов"
                    "field_branch_order" => "80"
                    "field_url" => null
                    "field_branch_type" => Illuminate\Database\Eloquent\Collection {#1178 …2}
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                    "field_h1" => null
                    "field_description_top" => null
                    "field_description_bottom" => null
                    "field_branch_cover" => []
                    "field_branch_covers" => []
                    "book" => Illuminate\Database\Eloquent\Collection {#1179 …2}
                    "branch_parent" => Illuminate\Database\Eloquent\Collection {#1180 …2}
                  ]
                  #changes: []
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                  #attributeCastCache: []
                  #dateFormat: null
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                  #touches: []
                  +timestamps: true
                  +usesUniqueIds: false
                  #hidden: []
                  #visible: []
                  #fillable: []
                  #guarded: array:1 [
                    0 => "*"
                  ]
                }
              ]
              #escapeWhenCastingToString: false
            }
          ]
          #original: array:24 [
            "id" => 1389619
            "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" => "376"
            "field_branch_display" => "0"
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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 {#1164}
            "branch_parent" => Illuminate\Database\Eloquent\Collection {#1177}
          ]
          #changes: []
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          +timestamps: true
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          #hidden: []
          #visible: []
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          #guarded: array:1 [
            0 => "*"
          ]
        }
      ]
      #escapeWhenCastingToString: false
    }
    "content" => Illuminate\Database\Eloquent\Collection {#1071
      #items: array:2 [
        0 => App\Models\Element {#1099
          #connection: "mysql"
          #table: "elements"
          #primaryKey: "id"
          #keyType: "int"
          +incrementing: true
          #with: []
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          #escapeWhenCastingToString: false
          #attributes: array:7 [
            "id" => 1640727
            "created_at" => "2026-04-10 13:58:26"
            "updated_at" => null
            "edition" => Illuminate\Database\Eloquent\Collection {#1089
              #items: array:1 [
                0 => App\Models\Edition {#1097
                  #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" => 5810
                    "created_at" => "2026-04-10 13:58:26"
                    "updated_at" => null
                    "title" => "Условие"
                    "field_order" => "1"
                    "field_publisher" => Illuminate\Database\Eloquent\Collection {#1095 …2}
                    "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 {#1096 …2}
                    "field_comment" => null
                    "field_similar_book" => Illuminate\Database\Eloquent\Collection {#1093 …2}
                    "field_process_formula" => "katex"
                    "field_edition_group" => Illuminate\Database\Eloquent\Collection {#1094 …2}
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                  ]
                  #original: array:21 [
                    "id" => 5810
                    "created_at" => "2026-04-10 13:58:26"
                    "updated_at" => null
                    "title" => "Условие"
                    "field_order" => "1"
                    "field_publisher" => Illuminate\Database\Eloquent\Collection {#1095 …2}
                    "field_content_type" => "free"
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                    "field_edition_type" => "statement"
                    "field_root_dir" => "0-"
                    "field_responsible" => Illuminate\Database\Eloquent\Collection {#1096 …2}
                    "field_comment" => null
                    "field_similar_book" => Illuminate\Database\Eloquent\Collection {#1093 …2}
                    "field_process_formula" => "katex"
                    "field_edition_group" => Illuminate\Database\Eloquent\Collection {#1094 …2}
                    "field_content_source" => null
                  ]
                  #changes: []
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                  #attributeCastCache: []
                  #dateFormat: null
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                  #touches: []
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                  #hidden: []
                  #visible: []
                  #fillable: []
                  #guarded: array:1 [
                    0 => "*"
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                }
              ]
              #escapeWhenCastingToString: false
            }
            "task" => array:2 [
              "refs" => "1390419"
              "type" => "task"
            ]
            "text" => "<p><strong>4.</strong> Три одинаковых точечных отрицательных заряда $q = -10 \text{ мкКл}$ расположены в вершинах равностороннего треугольника. Какой заряд следует поместить в центре треугольника, чтобы вся система зарядов находилась в равновесии?</p>"
            "img" => array:1 [
              0 => array:5 [
                "name" => "4-1.jpg"
                "alt" => null
                "width" => "1688"
                "height" => 224
                "path" => "/media/fizika_10/kasyanov-u/0-80zad/4-1.webp?ts=1757958169"
              ]
            ]
          ]
          #original: array:7 [
            "id" => 1640727
            "created_at" => "2026-04-10 13:58:26"
            "updated_at" => null
            "edition" => Illuminate\Database\Eloquent\Collection {#1089}
            "task" => array:2 [
              "refs" => "1390419"
              "type" => "task"
            ]
            "text" => "<p><strong>4.</strong> Три одинаковых точечных отрицательных заряда $q = -10 \text{ мкКл}$ расположены в вершинах равностороннего треугольника. Какой заряд следует поместить в центре треугольника, чтобы вся система зарядов находилась в равновесии?</p>"
            "img" => array:1 [
              0 => array:5 [
                "name" => "4-1.jpg"
                "alt" => null
                "width" => "1688"
                "height" => 224
                "path" => "/media/fizika_10/kasyanov-u/0-80zad/4-1.webp?ts=1757958169"
              ]
            ]
          ]
          #changes: []
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          #dateFormat: null
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          #touches: []
          +timestamps: true
          +usesUniqueIds: false
          #hidden: []
          #visible: []
          #fillable: []
          #guarded: array:1 [
            0 => "*"
          ]
        }
        1 => App\Models\Element {#1092
          #connection: "mysql"
          #table: "elements"
          #primaryKey: "id"
          #keyType: "int"
          +incrementing: true
          #with: []
          #withCount: []
          +preventsLazyLoading: false
          #perPage: 15
          +exists: true
          +wasRecentlyCreated: false
          #escapeWhenCastingToString: false
          #attributes: array:6 [
            "id" => 1693431
            "created_at" => "2026-04-10 13:58:26"
            "updated_at" => null
            "edition" => Illuminate\Database\Eloquent\Collection {#1083
              #items: array:1 [
                0 => App\Models\Edition {#1091
                  #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" => 6145
                    "created_at" => "2026-04-10 13:58:26"
                    "updated_at" => null
                    "title" => "Решение"
                    "field_order" => "2"
                    "field_publisher" => Illuminate\Database\Eloquent\Collection {#1087 …2}
                    "field_content_type" => "free"
                    "field_content_mode" => "text"
                    "field_page_content_mode" => ""
                    "field_content_text_checked" => null
                    "field_page_content_text_checked" => "0"
                    "field_solution_author" => "Gemini 2.5 Pro"
                    "field_moderator" => "tolik"
                    "field_edition_type" => "solution"
                    "field_root_dir" => "1-"
                    "field_responsible" => Illuminate\Database\Eloquent\Collection {#1088 …2}
                    "field_comment" => null
                    "field_similar_book" => Illuminate\Database\Eloquent\Collection {#1085 …2}
                    "field_process_formula" => "katex"
                    "field_edition_group" => Illuminate\Database\Eloquent\Collection {#1086 …2}
                    "field_content_source" => null
                  ]
                  #original: array:21 [
                    "id" => 6145
                    "created_at" => "2026-04-10 13:58:26"
                    "updated_at" => null
                    "title" => "Решение"
                    "field_order" => "2"
                    "field_publisher" => Illuminate\Database\Eloquent\Collection {#1087 …2}
                    "field_content_type" => "free"
                    "field_content_mode" => "text"
                    "field_page_content_mode" => ""
                    "field_content_text_checked" => null
                    "field_page_content_text_checked" => "0"
                    "field_solution_author" => "Gemini 2.5 Pro"
                    "field_moderator" => "tolik"
                    "field_edition_type" => "solution"
                    "field_root_dir" => "1-"
                    "field_responsible" => Illuminate\Database\Eloquent\Collection {#1088 …2}
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            "text" => "<p><strong>Дано:</strong></p><p>$q_1 = q_2 = q_3 = q = -10 \text{ мкКл}$</p><p>$q = -10 \times 10^{-6} \text{ Кл}$</p><p><strong>Найти:</strong></p><p>$Q$ - ?</p><p><strong>Решение:</strong></p><p>Для того чтобы система зарядов находилась в равновесии, необходимо, чтобы равнодействующая всех сил, действующих на каждый из зарядов, была равна нулю. В силу симметрии системы достаточно рассмотреть условие равновесия для одного из зарядов, расположенных в вершине треугольника. Пусть это будет заряд $q_1$.</p><p>На заряд $q_1$ действуют три силы:</p><ol><li>Сила Кулона со стороны заряда $q_2$, $\vec{F}_{21}$.</li><li>Сила Кулона со стороны заряда $q_3$, $\vec{F}_{31}$.</li><li>Сила Кулона со стороны центрального заряда $Q$, $\vec{F}_{Q1}$.</li></ol><p>Условие равновесия для заряда $q_1$ запишется в виде:</p><p>$\vec{F}_{21} + \vec{F}_{31} + \vec{F}_{Q1} = 0$</p><p>Заряды $q_1$, $q_2$ и $q_3$ одинаковы и отрицательны, поэтому силы $\vec{F}_{21}$ и $\vec{F}_{31}$ являются силами отталкивания. Пусть сторона равностороннего треугольника равна $a$. Тогда модули этих сил равны:</p><p>$F_{21} = F_{31} = k \frac{|q| \cdot |q|}{a^2} = k \frac{q^2}{a^2}$</p><p>где $k$ – постоянная Кулона. Угол между векторами $\vec{F}_{21}$ и $\vec{F}_{31}$ равен $60^\circ$, так как треугольник равносторонний.</p><p>Найдем равнодействующую этих двух сил $\vec{F}_R = \vec{F}_{21} + \vec{F}_{31}$. Ее модуль можно найти по теореме косинусов:</p><p>$F_R = \sqrt{F_{21}^2 + F_{31}^2 + 2 F_{21} F_{31} \cos(60^\circ)} = \sqrt{F_{21}^2 + F_{21}^2 + 2 F_{21}^2 \cdot \frac{1}{2}} = \sqrt{3F_{21}^2} = F_{21}\sqrt{3}$</p><p>$F_R = k \frac{q^2}{a^2}\sqrt{3}$</p><p>Вектор $\vec{F}_R$ направлен вдоль биссектрисы угла, то есть по линии, соединяющей вершину с центром треугольника, в сторону от центра.</p><p>Для того чтобы заряд $q_1$ находился в равновесии, сила $\vec{F}_{Q1}$ со стороны центрального заряда $Q$ должна быть равна по модулю и противоположна по направлению силе $\vec{F}_R$. Следовательно, сила $\vec{F}_{Q1}$ должна быть силой притяжения, а значит, заряд $Q$ должен быть положительным.</p><p>$\vec{F}_{Q1} = - \vec{F}_R \implies F_{Q1} = F_R$</p><p>Модуль силы $\vec{F}_{Q1}$ равен:</p><p>$F_{Q1} = k \frac{|Q| \cdot |q|}{r^2}$</p><p>где $r$ – расстояние от центра равностороннего треугольника до его вершины. Это расстояние равно $r = \frac{a}{\sqrt{3}}$.</p><p>Подставим выражение для $r$:</p><p>$F_{Q1} = k \frac{|Q||q|}{(a/\sqrt{3})^2} = 3k \frac{|Q||q|}{a^2}$</p><p>Теперь приравняем модули сил $F_R$ и $F_{Q1}$:</p><p>$k \frac{q^2}{a^2}\sqrt{3} = 3k \frac{|Q||q|}{a^2}$</p><p>Сократим одинаковые множители ($k, a^2, |q|$):</p><p>$|q|\sqrt{3} = 3|Q|$</p><p>Отсюда выразим модуль заряда $Q$:</p><p>$|Q| = \frac{|q|\sqrt{3}}{3} = \frac{|q|}{\sqrt{3}}$</p><p>Подставим числовое значение $|q| = 10$ мкКл:</p><p>$|Q| = \frac{10}{\sqrt{3}} \approx 5.77 \text{ мкКл}$</p><p>Так как заряд $Q$ должен быть положительным, то $Q \approx +5.77$ мкКл.</p><p>Проверим равновесие центрального заряда $Q$. Силы, действующие на него со стороны трех зарядов в вершинах, равны по модулю и направлены под углами $120^\circ$ друг к другу. Их векторная сумма равна нулю, так что центральный заряд также будет находиться в равновесии.</p><p><strong>Ответ:</strong></p><p>Чтобы вся система зарядов находилась в равновесии, в центре треугольника следует поместить положительный заряд $Q = \frac{|q|}{\sqrt{3}} \approx +5.77$ мкКл.</p>"
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            "text" => "<p><strong>Дано:</strong></p><p>$q_1 = q_2 = q_3 = q = -10 \text{ мкКл}$</p><p>$q = -10 \times 10^{-6} \text{ Кл}$</p><p><strong>Найти:</strong></p><p>$Q$ - ?</p><p><strong>Решение:</strong></p><p>Для того чтобы система зарядов находилась в равновесии, необходимо, чтобы равнодействующая всех сил, действующих на каждый из зарядов, была равна нулю. В силу симметрии системы достаточно рассмотреть условие равновесия для одного из зарядов, расположенных в вершине треугольника. Пусть это будет заряд $q_1$.</p><p>На заряд $q_1$ действуют три силы:</p><ol><li>Сила Кулона со стороны заряда $q_2$, $\vec{F}_{21}$.</li><li>Сила Кулона со стороны заряда $q_3$, $\vec{F}_{31}$.</li><li>Сила Кулона со стороны центрального заряда $Q$, $\vec{F}_{Q1}$.</li></ol><p>Условие равновесия для заряда $q_1$ запишется в виде:</p><p>$\vec{F}_{21} + \vec{F}_{31} + \vec{F}_{Q1} = 0$</p><p>Заряды $q_1$, $q_2$ и $q_3$ одинаковы и отрицательны, поэтому силы $\vec{F}_{21}$ и $\vec{F}_{31}$ являются силами отталкивания. Пусть сторона равностороннего треугольника равна $a$. Тогда модули этих сил равны:</p><p>$F_{21} = F_{31} = k \frac{|q| \cdot |q|}{a^2} = k \frac{q^2}{a^2}$</p><p>где $k$ – постоянная Кулона. Угол между векторами $\vec{F}_{21}$ и $\vec{F}_{31}$ равен $60^\circ$, так как треугольник равносторонний.</p><p>Найдем равнодействующую этих двух сил $\vec{F}_R = \vec{F}_{21} + \vec{F}_{31}$. Ее модуль можно найти по теореме косинусов:</p><p>$F_R = \sqrt{F_{21}^2 + F_{31}^2 + 2 F_{21} F_{31} \cos(60^\circ)} = \sqrt{F_{21}^2 + F_{21}^2 + 2 F_{21}^2 \cdot \frac{1}{2}} = \sqrt{3F_{21}^2} = F_{21}\sqrt{3}$</p><p>$F_R = k \frac{q^2}{a^2}\sqrt{3}$</p><p>Вектор $\vec{F}_R$ направлен вдоль биссектрисы угла, то есть по линии, соединяющей вершину с центром треугольника, в сторону от центра.</p><p>Для того чтобы заряд $q_1$ находился в равновесии, сила $\vec{F}_{Q1}$ со стороны центрального заряда $Q$ должна быть равна по модулю и противоположна по направлению силе $\vec{F}_R$. Следовательно, сила $\vec{F}_{Q1}$ должна быть силой притяжения, а значит, заряд $Q$ должен быть положительным.</p><p>$\vec{F}_{Q1} = - \vec{F}_R \implies F_{Q1} = F_R$</p><p>Модуль силы $\vec{F}_{Q1}$ равен:</p><p>$F_{Q1} = k \frac{|Q| \cdot |q|}{r^2}$</p><p>где $r$ – расстояние от центра равностороннего треугольника до его вершины. Это расстояние равно $r = \frac{a}{\sqrt{3}}$.</p><p>Подставим выражение для $r$:</p><p>$F_{Q1} = k \frac{|Q||q|}{(a/\sqrt{3})^2} = 3k \frac{|Q||q|}{a^2}$</p><p>Теперь приравняем модули сил $F_R$ и $F_{Q1}$:</p><p>$k \frac{q^2}{a^2}\sqrt{3} = 3k \frac{|Q||q|}{a^2}$</p><p>Сократим одинаковые множители ($k, a^2, |q|$):</p><p>$|q|\sqrt{3} = 3|Q|$</p><p>Отсюда выразим модуль заряда $Q$:</p><p>$|Q| = \frac{|q|\sqrt{3}}{3} = \frac{|q|}{\sqrt{3}}$</p><p>Подставим числовое значение $|q| = 10$ мкКл:</p><p>$|Q| = \frac{10}{\sqrt{3}} \approx 5.77 \text{ мкКл}$</p><p>Так как заряд $Q$ должен быть положительным, то $Q \approx +5.77$ мкКл.</p><p>Проверим равновесие центрального заряда $Q$. Силы, действующие на него со стороны трех зарядов в вершинах, равны по модулю и направлены под углами $120^\circ$ друг к другу. Их векторная сумма равна нулю, так что центральный заряд также будет находиться в равновесии.</p><p><strong>Ответ:</strong></p><p>Чтобы вся система зарядов находилась в равновесии, в центре треугольника следует поместить положительный заряд $Q = \frac{|q|}{\sqrt{3}} \approx +5.77$ мкКл.</p>"
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№4 (с. 376)
Условие. №4 (с. 376)
скриншот условия
Физика, 10 класс Учебник, автор: Касьянов Валерий Алексеевич, издательство Просвещение, Москва, 2021, белого цвета, страница 376, номер 4, Условие

4. Три одинаковых точечных отрицательных заряда $q = -10 \text{ мкКл}$ расположены в вершинах равностороннего треугольника. Какой заряд следует поместить в центре треугольника, чтобы вся система зарядов находилась в равновесии?

Решение. №4 (с. 376)

Дано:

$q_1 = q_2 = q_3 = q = -10 \text{ мкКл}$

$q = -10 \times 10^{-6} \text{ Кл}$

Найти:

$Q$ - ?

Решение:

Для того чтобы система зарядов находилась в равновесии, необходимо, чтобы равнодействующая всех сил, действующих на каждый из зарядов, была равна нулю. В силу симметрии системы достаточно рассмотреть условие равновесия для одного из зарядов, расположенных в вершине треугольника. Пусть это будет заряд $q_1$.

На заряд $q_1$ действуют три силы:

  1. Сила Кулона со стороны заряда $q_2$, $\vec{F}_{21}$.
  2. Сила Кулона со стороны заряда $q_3$, $\vec{F}_{31}$.
  3. Сила Кулона со стороны центрального заряда $Q$, $\vec{F}_{Q1}$.

Условие равновесия для заряда $q_1$ запишется в виде:

$\vec{F}_{21} + \vec{F}_{31} + \vec{F}_{Q1} = 0$

Заряды $q_1$, $q_2$ и $q_3$ одинаковы и отрицательны, поэтому силы $\vec{F}_{21}$ и $\vec{F}_{31}$ являются силами отталкивания. Пусть сторона равностороннего треугольника равна $a$. Тогда модули этих сил равны:

$F_{21} = F_{31} = k \frac{|q| \cdot |q|}{a^2} = k \frac{q^2}{a^2}$

где $k$ – постоянная Кулона. Угол между векторами $\vec{F}_{21}$ и $\vec{F}_{31}$ равен $60^\circ$, так как треугольник равносторонний.

Найдем равнодействующую этих двух сил $\vec{F}_R = \vec{F}_{21} + \vec{F}_{31}$. Ее модуль можно найти по теореме косинусов:

$F_R = \sqrt{F_{21}^2 + F_{31}^2 + 2 F_{21} F_{31} \cos(60^\circ)} = \sqrt{F_{21}^2 + F_{21}^2 + 2 F_{21}^2 \cdot \frac{1}{2}} = \sqrt{3F_{21}^2} = F_{21}\sqrt{3}$

$F_R = k \frac{q^2}{a^2}\sqrt{3}$

Вектор $\vec{F}_R$ направлен вдоль биссектрисы угла, то есть по линии, соединяющей вершину с центром треугольника, в сторону от центра.

Для того чтобы заряд $q_1$ находился в равновесии, сила $\vec{F}_{Q1}$ со стороны центрального заряда $Q$ должна быть равна по модулю и противоположна по направлению силе $\vec{F}_R$. Следовательно, сила $\vec{F}_{Q1}$ должна быть силой притяжения, а значит, заряд $Q$ должен быть положительным.

$\vec{F}_{Q1} = - \vec{F}_R \implies F_{Q1} = F_R$

Модуль силы $\vec{F}_{Q1}$ равен:

$F_{Q1} = k \frac{|Q| \cdot |q|}{r^2}$

где $r$ – расстояние от центра равностороннего треугольника до его вершины. Это расстояние равно $r = \frac{a}{\sqrt{3}}$.

Подставим выражение для $r$:

$F_{Q1} = k \frac{|Q||q|}{(a/\sqrt{3})^2} = 3k \frac{|Q||q|}{a^2}$

Теперь приравняем модули сил $F_R$ и $F_{Q1}$:

$k \frac{q^2}{a^2}\sqrt{3} = 3k \frac{|Q||q|}{a^2}$

Сократим одинаковые множители ($k, a^2, |q|$):

$|q|\sqrt{3} = 3|Q|$

Отсюда выразим модуль заряда $Q$:

$|Q| = \frac{|q|\sqrt{3}}{3} = \frac{|q|}{\sqrt{3}}$

Подставим числовое значение $|q| = 10$ мкКл:

$|Q| = \frac{10}{\sqrt{3}} \approx 5.77 \text{ мкКл}$

Так как заряд $Q$ должен быть положительным, то $Q \approx +5.77$ мкКл.

Проверим равновесие центрального заряда $Q$. Силы, действующие на него со стороны трех зарядов в вершинах, равны по модулю и направлены под углами $120^\circ$ друг к другу. Их векторная сумма равна нулю, так что центральный заряд также будет находиться в равновесии.

Ответ:

Чтобы вся система зарядов находилась в равновесии, в центре треугольника следует поместить положительный заряд $Q = \frac{|q|}{\sqrt{3}} \approx +5.77$ мкКл.

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