Номер 23.9, страница 167 - гдз по физике 10-11 класс задачник Гельфгат, Генденштейн

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

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

Тип: Задачник

Издательство: Илекса

Год издания: 2008 - 2026

Уровень обучения: профильный

Цвет обложки: красный лупа, парень едет на велосипеде

ISBN: 978-5-89237-252-7

Электродинамика. Электрическое поле. 23. Электрический заряд. Закон Кулона. Напряженность электрического поля. Упражнения - номер 23.9, страница 167.

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                              "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"
                          ]
                          #original: array:6 [
                            "id" => 5459
                            "created_at" => "2026-04-10 13:58:26"
                            "updated_at" => null
                            "name" => "10"
                            "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 => "*"
                          ]
                        }
                        1 => App\Models\Term {#1166
                          #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" => 5460
                            "created_at" => "2026-04-10 13:58:26"
                            "updated_at" => null
                            "name" => "11"
                            "field_cases" => array:6 [
                              "field_accusative_case" => "одиннадцатый"
                              "field_creative_case" => "одиннадцатым"
                              "field_dative_case" => "одиннадцатому"
                              "field_genitive_case" => "одинадцатого"
                              "field_nominative_case" => "одинадцатый"
                              "field_prepositional_case" => "одиннадцатом"
                            ]
                            "field_translit" => "odinadcatyj"
                          ]
                          #original: array:6 [
                            "id" => 5460
                            "created_at" => "2026-04-10 13:58:26"
                            "updated_at" => null
                            "name" => "11"
                            "field_cases" => array:6 [
                              "field_accusative_case" => "одиннадцатый"
                              "field_creative_case" => "одиннадцатым"
                              "field_dative_case" => "одиннадцатому"
                              "field_genitive_case" => "одинадцатого"
                              "field_nominative_case" => "одинадцатый"
                              "field_prepositional_case" => "одиннадцатом"
                            ]
                            "field_translit" => "odinadcatyj"
                          ]
                          #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 {#1167
                      #items: array:1 [
                        0 => App\Models\Term {#1168
                          #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" => 5158
                            "created_at" => "2026-04-10 13:58:26"
                            "updated_at" => null
                            "name" => "Илекса"
                            "field_cases" => null
                            "field_translit" => "ileksa"
                          ]
                          #original: array:6 [
                            "id" => 5158
                            "created_at" => "2026-04-10 13:58:26"
                            "updated_at" => null
                            "name" => "Илекса"
                            "field_cases" => null
                            "field_translit" => "ileksa"
                          ]
                          #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 {#1169
                      #items: array:3 [
                        0 => App\Models\Term {#1170
                          #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" => 4102
                            "created_at" => "2026-04-10 13:58:26"
                            "updated_at" => null
                            "name" => "Гельфгат"
                            "field_bio" => null
                            "field_degree_rp" => null
                            "field_foreign_lang_name" => null
                            "field_foreign_lang_patronymic" => null
                            "field_foreign_lang_surname" => null
                            "field_name" => "Илья"
                            "field_patronymic" => "Маркович"
                            "field_surname_rp" => null
                          ]
                          #original: array:12 [
                            "id" => 4102
                            "created_at" => "2026-04-10 13:58:26"
                            "updated_at" => null
                            "name" => "Гельфгат"
                            "field_bio" => null
                            "field_degree_rp" => null
                            "field_foreign_lang_name" => null
                            "field_foreign_lang_patronymic" => null
                            "field_foreign_lang_surname" => null
                            "field_name" => "Илья"
                            "field_patronymic" => "Маркович"
                            "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 => "*"
                          ]
                        }
                        1 => App\Models\Term {#1171
                          #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" => 4104
                            "created_at" => "2026-04-10 13:58:26"
                            "updated_at" => null
                            "name" => "Генденштейн"
                            "field_bio" => null
                            "field_degree_rp" => null
                            "field_foreign_lang_name" => null
                            "field_foreign_lang_patronymic" => null
                            "field_foreign_lang_surname" => null
                            "field_name" => "Лев"
                            "field_patronymic" => "Элевич"
                            "field_surname_rp" => "Генденштейна"
                          ]
                          #original: array:12 [
                            "id" => 4104
                            "created_at" => "2026-04-10 13:58:26"
                            "updated_at" => null
                            "name" => "Генденштейн"
                            "field_bio" => null
                            "field_degree_rp" => null
                            "field_foreign_lang_name" => null
                            "field_foreign_lang_patronymic" => null
                            "field_foreign_lang_surname" => null
                            "field_name" => "Лев"
                            "field_patronymic" => "Элевич"
                            "field_surname_rp" => "Генденштейна"
                          ]
                          #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\Term {#1172
                          #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" => 4583
                            "created_at" => "2026-04-10 13:58:26"
                            "updated_at" => null
                            "name" => "Кирик"
                            "field_bio" => null
                            "field_degree_rp" => null
                            "field_foreign_lang_name" => null
                            "field_foreign_lang_patronymic" => null
                            "field_foreign_lang_surname" => null
                            "field_name" => "Леонид"
                            "field_patronymic" => "Анатольевич"
                            "field_surname_rp" => null
                          ]
                          #original: array:12 [
                            "id" => 4583
                            "created_at" => "2026-04-10 13:58:26"
                            "updated_at" => null
                            "name" => "Кирик"
                            "field_bio" => null
                            "field_degree_rp" => null
                            "field_foreign_lang_name" => null
                            "field_foreign_lang_patronymic" => null
                            "field_foreign_lang_surname" => null
                            "field_name" => "Леонид"
                            "field_patronymic" => "Анатольевич"
                            "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 {#1173
                      #items: []
                      #escapeWhenCastingToString: false
                    }
                    "field_book_type" => Illuminate\Database\Eloquent\Collection {#1174
                      #items: array:1 [
                        0 => App\Models\Term {#1175
                          #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" => 6518
                            "created_at" => "2026-04-10 13:58:26"
                            "updated_at" => null
                            "name" => "Задачник"
                            "field_book_type_foreign" => null
                            "field_cases" => array:6 [
                              "field_accusative_case" => "задачник"
                              "field_creative_case" => "задачником"
                              "field_dative_case" => "задачнику"
                              "field_genitive_case" => "задачника"
                              "field_nominative_case" => "задачник"
                              "field_prepositional_case" => "задачнике"
                            ]
                            "field_plural_form" => null
                            "field_short_name" => null
                            "field_short_name_foreign" => null
                            "field_translit" => "zadachnik"
                          ]
                          #original: array:10 [
                            "id" => 6518
                            "created_at" => "2026-04-10 13:58:26"
                            "updated_at" => null
                            "name" => "Задачник"
                            "field_book_type_foreign" => null
                            "field_cases" => array:6 [
                              "field_accusative_case" => "задачник"
                              "field_creative_case" => "задачником"
                              "field_dative_case" => "задачнику"
                              "field_genitive_case" => "задачника"
                              "field_nominative_case" => "задачник"
                              "field_prepositional_case" => "задачнике"
                            ]
                            "field_plural_form" => null
                            "field_short_name" => null
                            "field_short_name_foreign" => null
                            "field_translit" => "zadachnik"
                          ]
                          #changes: []
                          #casts: []
                          #classCastCache: []
                          #attributeCastCache: []
                          #dateFormat: null
                          #appends: []
                          #dispatchesEvents: []
                          #observables: []
                          #relations: []
                          #touches: []
                          +timestamps: true
                          +usesUniqueIds: false
                          #hidden: []
                          #visible: []
                          #fillable: []
                          #guarded: array:1 [
                            0 => "*"
                          ]
                        }
                      ]
                      #escapeWhenCastingToString: false
                    }
                    "field_country" => Illuminate\Database\Eloquent\Collection {#1176
                      #items: array:1 [
                        0 => App\Models\Term {#1177
                          #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 {#1178
                      #items: array:1 [
                        0 => App\Models\Term {#1179
                          #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 {#1180
                      #items: []
                      #escapeWhenCastingToString: false
                    }
                    "field_umk" => Illuminate\Database\Eloquent\Collection {#1181
                      #items: []
                      #escapeWhenCastingToString: false
                    }
                    "field_level_of_education" => Illuminate\Database\Eloquent\Collection {#1182
                      #items: array:1 [
                        0 => App\Models\Term {#1183
                          #connection: "mysql"
                          #table: "terms"
                          #primaryKey: "id"
                          #keyType: "int"
                          +incrementing: false
                          #with: []
                          #withCount: []
                          +preventsLazyLoading: false
                          #perPage: 15
                          +exists: true
                          +wasRecentlyCreated: false
                          #escapeWhenCastingToString: false
                          #attributes: array:6 [
                            "id" => 40
                            "created_at" => "2026-04-10 13:58:26"
                            "updated_at" => null
                            "name" => "профильный"
                            "field_cases" => array:6 [
                              "field_accusative_case" => "профильный"
                              "field_creative_case" => "профильным"
                              "field_dative_case" => "профильному"
                              "field_genitive_case" => "профильного"
                              "field_nominative_case" => "профильный"
                              "field_prepositional_case" => "профильном"
                            ]
                            "field_translit" => "profilnyy"
                          ]
                          #original: array:6 [
                            "id" => 40
                            "created_at" => "2026-04-10 13:58:26"
                            "updated_at" => null
                            "name" => "профильный"
                            "field_cases" => array:6 [
                              "field_accusative_case" => "профильный"
                              "field_creative_case" => "профильным"
                              "field_dative_case" => "профильному"
                              "field_genitive_case" => "профильного"
                              "field_nominative_case" => "профильный"
                              "field_prepositional_case" => "профильном"
                            ]
                            "field_translit" => "profilnyy"
                          ]
                          #changes: []
                          #casts: []
                          #classCastCache: []
                          #attributeCastCache: []
                          #dateFormat: null
                          #appends: []
                          #dispatchesEvents: []
                          #observables: []
                          #relations: []
                          #touches: []
                          +timestamps: true
                          +usesUniqueIds: false
                          #hidden: []
                          #visible: []
                          #fillable: []
                          #guarded: array:1 [
                            0 => "*"
                          ]
                        }
                      ]
                      #escapeWhenCastingToString: false
                    }
                    "field_standart_of_education" => Illuminate\Database\Eloquent\Collection {#1184
                      #items: []
                      #escapeWhenCastingToString: false
                    }
                    "field_publication_number" => null
                    "field_publication_type" => Illuminate\Database\Eloquent\Collection {#1185
                      #items: []
                      #escapeWhenCastingToString: false
                    }
                    "field_under_the_edition" => Illuminate\Database\Eloquent\Collection {#1186
                      #items: []
                      #escapeWhenCastingToString: false
                    }
                    "field_under_the_edition_degree" => null
                    "field_cover_description" => "лупа, парень едет на велосипеде"
                    "field_publication_year" => "2008"
                    "field_publication_year_until" => null
                    "field_part" => ""
                    "field_part_writing" => ""
                    "field_second_foreign_language" => null
                    "field_for_whom" => "Учебное издание"
                    "field_allowed" => null
                    "field_reserve_field" => null
                    "field_link_to_source" => null
                    "field_tasks_count" => "459"
                    "field_priority" => null
                    "field_default_folder" => "/fizika_10/gelfgat-z/"
                    "field_isbn" => "978-5-89237-252-7"
                    "field_cover" => array:1 [
                      0 => "/media/fizika_10/gelfgat-z/covers/cover1.webp?ts=1756049816"
                    ]
                    "field_cover_alts" => array:1 [
                      0 => ""
                    ]
                    "field_covers" => array:1 [
                      0 => array:4 [
                        "path" => "/media/fizika_10/gelfgat-z/covers/cover1.webp?ts=1756049816"
                        "alt" => ""
                        "width" => "1566"
                        "height" => "2412"
                      ]
                    ]
                    "field_popular_book" => "0"
                    "field_recommended_books" => Illuminate\Database\Eloquent\Collection {#1187
                      #items: []
                      #escapeWhenCastingToString: false
                    }
                    "field_new_book" => Illuminate\Database\Eloquent\Collection {#1188
                      #items: []
                      #escapeWhenCastingToString: false
                    }
                    "field_old_book" => Illuminate\Database\Eloquent\Collection {#1189
                      #items: []
                      #escapeWhenCastingToString: false
                    }
                    "field_url" => "/10-klass/fizika/gelfgat-zadachnik"
                    "field_cover_color" => Illuminate\Database\Eloquent\Collection {#1190
                      #items: array:1 [
                        0 => App\Models\Term {#1191
                          #connection: "mysql"
                          #table: "terms"
                          #primaryKey: "id"
                          #keyType: "int"
                          +incrementing: false
                          #with: []
                          #withCount: []
                          +preventsLazyLoading: false
                          #perPage: 15
                          +exists: true
                          +wasRecentlyCreated: false
                          #escapeWhenCastingToString: false
                          #attributes: array:6 [
                            "id" => 46
                            "created_at" => "2026-04-10 13:58:26"
                            "updated_at" => null
                            "name" => "красный"
                            "field_cases" => array:6 [
                              "field_accusative_case" => "красный"
                              "field_creative_case" => "красным"
                              "field_dative_case" => "красному"
                              "field_genitive_case" => "красного"
                              "field_nominative_case" => "красный"
                              "field_prepositional_case" => "красном"
                            ]
                            "field_translit" => "krasnyy"
                          ]
                          #original: array:6 [
                            "id" => 46
                            "created_at" => "2026-04-10 13:58:26"
                            "updated_at" => null
                            "name" => "красный"
                            "field_cases" => array:6 [
                              "field_accusative_case" => "красный"
                              "field_creative_case" => "красным"
                              "field_dative_case" => "красному"
                              "field_genitive_case" => "красного"
                              "field_nominative_case" => "красный"
                              "field_prepositional_case" => "красном"
                            ]
                            "field_translit" => "krasnyy"
                          ]
                          #changes: []
                          #casts: []
                          #classCastCache: []
                          #attributeCastCache: []
                          #dateFormat: null
                          #appends: []
                          #dispatchesEvents: []
                          #observables: []
                          #relations: []
                          #touches: []
                          +timestamps: true
                          +usesUniqueIds: false
                          #hidden: []
                          #visible: []
                          #fillable: []
                          #guarded: array:1 [
                            0 => "*"
                          ]
                        }
                      ]
                      #escapeWhenCastingToString: false
                    }
                    "field_metatags_title" => null
                    "field_metatags_description" => null
                    "field_h1" => null
                    "field_description_top" => null
                    "field_description_bottom" => null
                    "breadcrumbs" => array:3 [
                      "class" => 381
                      "subject" => 556
                      "class_subject" => 494
                    ]
                  ]
                  #original: array:50 [
                    "id" => 5400
                    "created_at" => "2026-04-10 13:58:26"
                    "updated_at" => null
                    "field_tree_default_status" => "tasks"
                    "field_pages_status" => null
                    "field_subject" => Illuminate\Database\Eloquent\Collection {#1163}
                    "field_class" => Illuminate\Database\Eloquent\Collection {#1164}
                    "field_publisher" => Illuminate\Database\Eloquent\Collection {#1167}
                    "field_author" => Illuminate\Database\Eloquent\Collection {#1169}
                    "field_author_foreign" => Illuminate\Database\Eloquent\Collection {#1173}
                    "field_book_type" => Illuminate\Database\Eloquent\Collection {#1174}
                    "field_country" => Illuminate\Database\Eloquent\Collection {#1176}
                    "field_city" => Illuminate\Database\Eloquent\Collection {#1178}
                    "field_series" => Illuminate\Database\Eloquent\Collection {#1180}
                    "field_umk" => Illuminate\Database\Eloquent\Collection {#1181}
                    "field_level_of_education" => Illuminate\Database\Eloquent\Collection {#1182}
                    "field_standart_of_education" => Illuminate\Database\Eloquent\Collection {#1184}
                    "field_publication_number" => null
                    "field_publication_type" => Illuminate\Database\Eloquent\Collection {#1185}
                    "field_under_the_edition" => Illuminate\Database\Eloquent\Collection {#1186}
                    "field_under_the_edition_degree" => null
                    "field_cover_description" => "лупа, парень едет на велосипеде"
                    "field_publication_year" => "2008"
                    "field_publication_year_until" => null
                    "field_part" => ""
                    "field_part_writing" => ""
                    "field_second_foreign_language" => null
                    "field_for_whom" => "Учебное издание"
                    "field_allowed" => null
                    "field_reserve_field" => null
                    "field_link_to_source" => null
                    "field_tasks_count" => "459"
                    "field_priority" => null
                    "field_default_folder" => "/fizika_10/gelfgat-z/"
                    "field_isbn" => "978-5-89237-252-7"
                    "field_cover" => array:1 [
                      0 => "/media/fizika_10/gelfgat-z/covers/cover1.webp?ts=1756049816"
                    ]
                    "field_cover_alts" => array:1 [
                      0 => ""
                    ]
                    "field_covers" => array:1 [
                      0 => array:4 [
                        "path" => "/media/fizika_10/gelfgat-z/covers/cover1.webp?ts=1756049816"
                        "alt" => ""
                        "width" => "1566"
                        "height" => "2412"
                      ]
                    ]
                    "field_popular_book" => "0"
                    "field_recommended_books" => Illuminate\Database\Eloquent\Collection {#1187}
                    "field_new_book" => Illuminate\Database\Eloquent\Collection {#1188}
                    "field_old_book" => Illuminate\Database\Eloquent\Collection {#1189}
                    "field_url" => "/10-klass/fizika/gelfgat-zadachnik"
                    "field_cover_color" => Illuminate\Database\Eloquent\Collection {#1190}
                    "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 {#1192
              #items: []
              #escapeWhenCastingToString: false
            }
          ]
          #original: array:24 [
            "id" => 1319339
            "created_at" => "2026-04-10 13:58:26"
            "updated_at" => null
            "field_display_title" => "Электродинамика"
            "field_branch_order" => null
            "field_url" => null
            "field_branch_type" => Illuminate\Database\Eloquent\Collection {#1160}
            "field_page_start" => "163"
            "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 {#1194}
            "branch_parent" => Illuminate\Database\Eloquent\Collection {#1192}
          ]
          #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 {#1193
          #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" => 1319340
            "created_at" => "2026-04-10 13:58:26"
            "updated_at" => null
            "field_display_title" => "Электрическое поле"
            "field_branch_order" => null
            "field_url" => null
            "field_branch_type" => Illuminate\Database\Eloquent\Collection {#1195
              #items: []
              #escapeWhenCastingToString: false
            }
            "field_page_start" => "163"
            "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 {#1196
              #items: array:1 [
                0 => App\Models\Book {#1161}
              ]
              #escapeWhenCastingToString: false
            }
            "branch_parent" => Illuminate\Database\Eloquent\Collection {#1197
              #items: array:1 [
                0 => App\Models\Branch {#1034}
              ]
              #escapeWhenCastingToString: false
            }
          ]
          #original: array:24 [
            "id" => 1319340
            "created_at" => "2026-04-10 13:58:26"
            "updated_at" => null
            "field_display_title" => "Электрическое поле"
            "field_branch_order" => null
            "field_url" => null
            "field_branch_type" => Illuminate\Database\Eloquent\Collection {#1195}
            "field_page_start" => "163"
            "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 {#1196}
            "branch_parent" => Illuminate\Database\Eloquent\Collection {#1197}
          ]
          #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 {#1198
          #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" => 1319341
            "created_at" => "2026-04-10 13:58:26"
            "updated_at" => null
            "field_display_title" => "23. Электрический заряд. Закон Кулона. Напряженность электрического поля"
            "field_branch_order" => null
            "field_url" => null
            "field_branch_type" => Illuminate\Database\Eloquent\Collection {#1199
              #items: []
              #escapeWhenCastingToString: false
            }
            "field_page_start" => "163"
            "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 {#1200
              #items: array:1 [
                0 => App\Models\Book {#1161}
              ]
              #escapeWhenCastingToString: false
            }
            "branch_parent" => Illuminate\Database\Eloquent\Collection {#1242
              #items: array:1 [
                0 => App\Models\Branch {#1201
                  #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" => 1319340
                    "created_at" => "2026-04-10 13:58:26"
                    "updated_at" => null
                    "field_display_title" => "Электрическое поле"
                    "field_branch_order" => null
                    "field_url" => null
                    "field_branch_type" => Illuminate\Database\Eloquent\Collection {#1203
                      #items: []
                      #escapeWhenCastingToString: false
                    }
                    "field_page_start" => "163"
                    "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 {#1202
                      #items: array:1 [
                        0 => App\Models\Book {#1204 …30}
                      ]
                      #escapeWhenCastingToString: false
                    }
                    "branch_parent" => Illuminate\Database\Eloquent\Collection {#1235
                      #items: array:1 [
                        0 => App\Models\Branch {#1236 …30}
                      ]
                      #escapeWhenCastingToString: false
                    }
                  ]
                  #original: array:24 [
                    "id" => 1319340
                    "created_at" => "2026-04-10 13:58:26"
                    "updated_at" => null
                    "field_display_title" => "Электрическое поле"
                    "field_branch_order" => null
                    "field_url" => null
                    "field_branch_type" => Illuminate\Database\Eloquent\Collection {#1203}
                    "field_page_start" => "163"
                    "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 {#1202}
                    "branch_parent" => Illuminate\Database\Eloquent\Collection {#1235}
                  ]
                  #changes: []
                  #casts: []
                  #classCastCache: []
                  #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" => 1319341
            "created_at" => "2026-04-10 13:58:26"
            "updated_at" => null
            "field_display_title" => "23. Электрический заряд. Закон Кулона. Напряженность электрического поля"
            "field_branch_order" => null
            "field_url" => null
            "field_branch_type" => Illuminate\Database\Eloquent\Collection {#1199}
            "field_page_start" => "163"
            "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 {#1200}
            "branch_parent" => Illuminate\Database\Eloquent\Collection {#1242}
          ]
          #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 {#1240
          #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" => 1319342
            "created_at" => "2026-04-10 13:58:26"
            "updated_at" => null
            "field_display_title" => "Упражнения"
            "field_branch_order" => null
            "field_url" => null
            "field_branch_type" => Illuminate\Database\Eloquent\Collection {#1241
              #items: []
              #escapeWhenCastingToString: false
            }
            "field_page_start" => "163"
            "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 {#1243
              #items: array:1 [
                0 => App\Models\Book {#1161}
              ]
              #escapeWhenCastingToString: false
            }
            "branch_parent" => Illuminate\Database\Eloquent\Collection {#1252
              #items: array:1 [
                0 => App\Models\Branch {#1251
                  #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" => 1319341
                    "created_at" => "2026-04-10 13:58:26"
                    "updated_at" => null
                    "field_display_title" => "23. Электрический заряд. Закон Кулона. Напряженность электрического поля"
                    "field_branch_order" => null
                    "field_url" => null
                    "field_branch_type" => Illuminate\Database\Eloquent\Collection {#1253
                      #items: []
                      #escapeWhenCastingToString: false
                    }
                    "field_page_start" => "163"
                    "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 {#1254
                      #items: array:1 [
                        0 => App\Models\Book {#1161}
                      ]
                      #escapeWhenCastingToString: false
                    }
                    "branch_parent" => Illuminate\Database\Eloquent\Collection {#1255
                      #items: array:1 [
                        0 => App\Models\Branch {#1201}
                      ]
                      #escapeWhenCastingToString: false
                    }
                  ]
                  #original: array:24 [
                    "id" => 1319341
                    "created_at" => "2026-04-10 13:58:26"
                    "updated_at" => null
                    "field_display_title" => "23. Электрический заряд. Закон Кулона. Напряженность электрического поля"
                    "field_branch_order" => null
                    "field_url" => null
                    "field_branch_type" => Illuminate\Database\Eloquent\Collection {#1253}
                    "field_page_start" => "163"
                    "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 {#1254}
                    "branch_parent" => Illuminate\Database\Eloquent\Collection {#1255}
                  ]
                  #changes: []
                  #casts: []
                  #classCastCache: []
                  #attributeCastCache: []
                  #dateFormat: null
                  #appends: []
                  #dispatchesEvents: []
                  #observables: []
                  #relations: []
                  #touches: []
                  +timestamps: true
                  +usesUniqueIds: false
                  #hidden: []
                  #visible: []
                  #fillable: []
                  #guarded: array:1 [
                    0 => "*"
                  ]
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            "text" => "<p><strong>23.9.</strong> На нитях равной длины, закрепленных в одной точке, висят два одинаковых маленьких металлических шарика. Шарикам сообщили равные заряды, в результате чего они разошлись на расстояние $a = 9,5 \text{ см}$, которое намного меньше длины нитей. Затем один из шариков разрядили. Что произойдет с шариками после этого? При каком расстоянии $\text{b}$ между шариками снова установится равновесие?</p><p>&#9745; $b = 6 \text{ см}$.</p><p><strong><em>Решение.</em></strong> После разрядки одного из шариков отталкивание сменится притяжением, шарики соприкоснутся, при этом заряд $\text{q}$ одного из них разделится между шариками поровну. В результате опять возникнет отталкивание, но слабее первоначального. Найдем характер зависимости расстояния между шариками от заряда шариков. Из соотношения $F_к = k\frac{q^2}{a^2} = mg \operatorname{tg}\frac{\alpha}{2}$ (см. задачу 23.8) с учетом соотношения $a = 2l \sin\frac{\alpha}{2}$ и того, что $\alpha \ll 1$, получаем</p><p>$a = \left(\frac{2klq^2}{mg}\right)^{1/3}$. Заменяя $\text{q}$ на $q/2$, находим $b = \frac{a}{4^{1/3}} = 6 \text{ (см)}$.</p>"
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            "text" => "<p><strong>23.9.</strong> На нитях равной длины, закрепленных в одной точке, висят два одинаковых маленьких металлических шарика. Шарикам сообщили равные заряды, в результате чего они разошлись на расстояние $a = 9,5 \text{ см}$, которое намного меньше длины нитей. Затем один из шариков разрядили. Что произойдет с шариками после этого? При каком расстоянии $\text{b}$ между шариками снова установится равновесие?</p><p>&#9745; $b = 6 \text{ см}$.</p><p><strong><em>Решение.</em></strong> После разрядки одного из шариков отталкивание сменится притяжением, шарики соприкоснутся, при этом заряд $\text{q}$ одного из них разделится между шариками поровну. В результате опять возникнет отталкивание, но слабее первоначального. Найдем характер зависимости расстояния между шариками от заряда шариков. Из соотношения $F_к = k\frac{q^2}{a^2} = mg \operatorname{tg}\frac{\alpha}{2}$ (см. задачу 23.8) с учетом соотношения $a = 2l \sin\frac{\alpha}{2}$ и того, что $\alpha \ll 1$, получаем</p><p>$a = \left(\frac{2klq^2}{mg}\right)^{1/3}$. Заменяя $\text{q}$ на $q/2$, находим $b = \frac{a}{4^{1/3}} = 6 \text{ (см)}$.</p>"
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            "text" => "<p><strong>Дано</strong></p><p>Два одинаковых шарика массой $m$ и зарядом $q$.<br>Длина нитей: $l$.<br>Начальное расстояние равновесия: $a = 9,5$ см.<br>Условие малых углов: $a \ll l$.<br>После разрядки одного шарика и их соприкосновения новые заряды равны $q' = q/2$.</p><p><i>Перевод в систему СИ:</i><br>$a = 9,5 \text{ см} = 0,095 \text{ м}$.</p><p><strong>Найти:</strong></p><p>Новое расстояние равновесия $b$.</p><p><strong>Решение</strong></p><p>Рассмотрим состояние равновесия для одного из шариков в начальный момент. На него действуют три силы: сила тяжести $F_g = mg$, направленная вертикально вниз, сила натяжения нити $T$, направленная вдоль нити, и сила Кулона $F_e$, направленная горизонтально.</p><p>Пусть нить отклонена от вертикали на малый угол $\alpha$. Условие равновесия в проекциях на горизонтальную и вертикальную оси:</p><p>$T \sin \alpha = F_e$ (1)<br>$T \cos \alpha = mg$ (2)</p><p>Разделим уравнение (1) на (2):</p><p>$\frac{T \sin \alpha}{T \cos \alpha} = \frac{F_e}{mg} \Rightarrow \text{tg} \alpha = \frac{F_e}{mg}$</p><p>Сила Кулоновского отталкивания между шариками с одинаковыми зарядами $q$ на расстоянии $a$:</p><p>$F_e = k \frac{q^2}{a^2}$</p><p>где $k$ – коэффициент пропорциональности в законе Кулона.</p><p>Из геометрии системы, для малого угла $\alpha$ (так как $a \ll l$), можно записать:</p><p>$\text{tg} \alpha \approx \sin \alpha = \frac{a/2}{l} = \frac{a}{2l}$</p><p>Подставим выражения для $\text{tg} \alpha$ и $F_e$ в условие равновесия:</p><p>$\frac{a}{2l} = \frac{k q^2 / a^2}{mg} = \frac{k q^2}{mg a^2}$</p><p>Выразим отсюда $a^3$:</p><p>$a^3 = \frac{2klq^2}{mg}$ (3)</p><p>Теперь рассмотрим, что произойдет после разрядки одного из шариков. Его заряд станет равен нулю. Между заряженным шариком (с зарядом $q$) и нейтральным возникнет сила притяжения за счет электростатической индукции. Шарики притянутся, соприкоснутся. Поскольку шарики одинаковые и металлические, общий заряд $q+0=q$ распределится между ними поровну. Новый заряд каждого шарика станет:</p><p>$q' = \frac{q}{2}$</p><p>После этого шарики, имея одноименные заряды $q'$, снова оттолкнутся и установятся в новом положении равновесия на расстоянии $b$. Запишем для нового состояния равновесия аналогичное уравнение, заменив $a$ на $b$ и $q$ на $q'$:</p><p>$b^3 = \frac{2kl(q')^2}{mg}$</p><p>Подставим значение $q' = q/2$:</p><p>$b^3 = \frac{2kl(q/2)^2}{mg} = \frac{2klq^2}{4mg} = \frac{1}{4} \left( \frac{2klq^2}{mg} \right)$</p><p>Заметим, что выражение в скобках равно $a^3$ из уравнения (3). Таким образом:</p><p>$b^3 = \frac{a^3}{4}$</p><p>Отсюда находим новое расстояние $b$:</p><p>$b = \sqrt[3]{\frac{a^3}{4}} = \frac{a}{\sqrt[3]{4}}$</p><p>Подставим числовое значение $a = 9,5$ см:</p><p>$b = \frac{9,5 \text{ см}}{\sqrt[3]{4}} \approx \frac{9,5 \text{ см}}{1,5874} \approx 5,984 \text{ см}$</p><p>Округляя результат, получаем $b \approx 6$ см.</p><p><strong>Ответ:</strong> После разрядки одного из шариков они притянутся, соприкоснутся, и заряд перераспределится поровну. Затем они оттолкнутся и установятся в новом положении равновесия на расстоянии $b = \frac{a}{\sqrt[3]{4}} \approx 6 \text{ см}$.</p>"
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            "text" => "<p><strong>Дано</strong></p><p>Два одинаковых шарика массой $m$ и зарядом $q$.<br>Длина нитей: $l$.<br>Начальное расстояние равновесия: $a = 9,5$ см.<br>Условие малых углов: $a \ll l$.<br>После разрядки одного шарика и их соприкосновения новые заряды равны $q' = q/2$.</p><p><i>Перевод в систему СИ:</i><br>$a = 9,5 \text{ см} = 0,095 \text{ м}$.</p><p><strong>Найти:</strong></p><p>Новое расстояние равновесия $b$.</p><p><strong>Решение</strong></p><p>Рассмотрим состояние равновесия для одного из шариков в начальный момент. На него действуют три силы: сила тяжести $F_g = mg$, направленная вертикально вниз, сила натяжения нити $T$, направленная вдоль нити, и сила Кулона $F_e$, направленная горизонтально.</p><p>Пусть нить отклонена от вертикали на малый угол $\alpha$. Условие равновесия в проекциях на горизонтальную и вертикальную оси:</p><p>$T \sin \alpha = F_e$ (1)<br>$T \cos \alpha = mg$ (2)</p><p>Разделим уравнение (1) на (2):</p><p>$\frac{T \sin \alpha}{T \cos \alpha} = \frac{F_e}{mg} \Rightarrow \text{tg} \alpha = \frac{F_e}{mg}$</p><p>Сила Кулоновского отталкивания между шариками с одинаковыми зарядами $q$ на расстоянии $a$:</p><p>$F_e = k \frac{q^2}{a^2}$</p><p>где $k$ – коэффициент пропорциональности в законе Кулона.</p><p>Из геометрии системы, для малого угла $\alpha$ (так как $a \ll l$), можно записать:</p><p>$\text{tg} \alpha \approx \sin \alpha = \frac{a/2}{l} = \frac{a}{2l}$</p><p>Подставим выражения для $\text{tg} \alpha$ и $F_e$ в условие равновесия:</p><p>$\frac{a}{2l} = \frac{k q^2 / a^2}{mg} = \frac{k q^2}{mg a^2}$</p><p>Выразим отсюда $a^3$:</p><p>$a^3 = \frac{2klq^2}{mg}$ (3)</p><p>Теперь рассмотрим, что произойдет после разрядки одного из шариков. Его заряд станет равен нулю. Между заряженным шариком (с зарядом $q$) и нейтральным возникнет сила притяжения за счет электростатической индукции. Шарики притянутся, соприкоснутся. Поскольку шарики одинаковые и металлические, общий заряд $q+0=q$ распределится между ними поровну. Новый заряд каждого шарика станет:</p><p>$q' = \frac{q}{2}$</p><p>После этого шарики, имея одноименные заряды $q'$, снова оттолкнутся и установятся в новом положении равновесия на расстоянии $b$. Запишем для нового состояния равновесия аналогичное уравнение, заменив $a$ на $b$ и $q$ на $q'$:</p><p>$b^3 = \frac{2kl(q')^2}{mg}$</p><p>Подставим значение $q' = q/2$:</p><p>$b^3 = \frac{2kl(q/2)^2}{mg} = \frac{2klq^2}{4mg} = \frac{1}{4} \left( \frac{2klq^2}{mg} \right)$</p><p>Заметим, что выражение в скобках равно $a^3$ из уравнения (3). Таким образом:</p><p>$b^3 = \frac{a^3}{4}$</p><p>Отсюда находим новое расстояние $b$:</p><p>$b = \sqrt[3]{\frac{a^3}{4}} = \frac{a}{\sqrt[3]{4}}$</p><p>Подставим числовое значение $a = 9,5$ см:</p><p>$b = \frac{9,5 \text{ см}}{\sqrt[3]{4}} \approx \frac{9,5 \text{ см}}{1,5874} \approx 5,984 \text{ см}$</p><p>Округляя результат, получаем $b \approx 6$ см.</p><p><strong>Ответ:</strong> После разрядки одного из шариков они притянутся, соприкоснутся, и заряд перераспределится поровну. Затем они оттолкнутся и установятся в новом положении равновесия на расстоянии $b = \frac{a}{\sqrt[3]{4}} \approx 6 \text{ см}$.</p>"
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№23.9 (с. 167)
Условие. №23.9 (с. 167)
скриншот условия
Физика, 10-11 класс Задачник, авторы: Гельфгат Илья Маркович, Генденштейн Лев Элевич, Кирик Леонид Анатольевич, издательство Илекса, Москва, 2008, красного цвета, страница 167, номер 23.9, Условие

23.9. На нитях равной длины, закрепленных в одной точке, висят два одинаковых маленьких металлических шарика. Шарикам сообщили равные заряды, в результате чего они разошлись на расстояние $a = 9,5 \text{ см}$, которое намного меньше длины нитей. Затем один из шариков разрядили. Что произойдет с шариками после этого? При каком расстоянии $\text{b}$ между шариками снова установится равновесие?

☑ $b = 6 \text{ см}$.

Решение. После разрядки одного из шариков отталкивание сменится притяжением, шарики соприкоснутся, при этом заряд $\text{q}$ одного из них разделится между шариками поровну. В результате опять возникнет отталкивание, но слабее первоначального. Найдем характер зависимости расстояния между шариками от заряда шариков. Из соотношения $F_к = k\frac{q^2}{a^2} = mg \operatorname{tg}\frac{\alpha}{2}$ (см. задачу 23.8) с учетом соотношения $a = 2l \sin\frac{\alpha}{2}$ и того, что $\alpha \ll 1$, получаем

$a = \left(\frac{2klq^2}{mg}\right)^{1/3}$. Заменяя $\text{q}$ на $q/2$, находим $b = \frac{a}{4^{1/3}} = 6 \text{ (см)}$.

Решение. №23.9 (с. 167)

Дано

Два одинаковых шарика массой $m$ и зарядом $q$.
Длина нитей: $l$.
Начальное расстояние равновесия: $a = 9,5$ см.
Условие малых углов: $a \ll l$.
После разрядки одного шарика и их соприкосновения новые заряды равны $q' = q/2$.

Перевод в систему СИ:
$a = 9,5 \text{ см} = 0,095 \text{ м}$.

Найти:

Новое расстояние равновесия $b$.

Решение

Рассмотрим состояние равновесия для одного из шариков в начальный момент. На него действуют три силы: сила тяжести $F_g = mg$, направленная вертикально вниз, сила натяжения нити $T$, направленная вдоль нити, и сила Кулона $F_e$, направленная горизонтально.

Пусть нить отклонена от вертикали на малый угол $\alpha$. Условие равновесия в проекциях на горизонтальную и вертикальную оси:

$T \sin \alpha = F_e$ (1)
$T \cos \alpha = mg$ (2)

Разделим уравнение (1) на (2):

$\frac{T \sin \alpha}{T \cos \alpha} = \frac{F_e}{mg} \Rightarrow \text{tg} \alpha = \frac{F_e}{mg}$

Сила Кулоновского отталкивания между шариками с одинаковыми зарядами $q$ на расстоянии $a$:

$F_e = k \frac{q^2}{a^2}$

где $k$ – коэффициент пропорциональности в законе Кулона.

Из геометрии системы, для малого угла $\alpha$ (так как $a \ll l$), можно записать:

$\text{tg} \alpha \approx \sin \alpha = \frac{a/2}{l} = \frac{a}{2l}$

Подставим выражения для $\text{tg} \alpha$ и $F_e$ в условие равновесия:

$\frac{a}{2l} = \frac{k q^2 / a^2}{mg} = \frac{k q^2}{mg a^2}$

Выразим отсюда $a^3$:

$a^3 = \frac{2klq^2}{mg}$ (3)

Теперь рассмотрим, что произойдет после разрядки одного из шариков. Его заряд станет равен нулю. Между заряженным шариком (с зарядом $q$) и нейтральным возникнет сила притяжения за счет электростатической индукции. Шарики притянутся, соприкоснутся. Поскольку шарики одинаковые и металлические, общий заряд $q+0=q$ распределится между ними поровну. Новый заряд каждого шарика станет:

$q' = \frac{q}{2}$

После этого шарики, имея одноименные заряды $q'$, снова оттолкнутся и установятся в новом положении равновесия на расстоянии $b$. Запишем для нового состояния равновесия аналогичное уравнение, заменив $a$ на $b$ и $q$ на $q'$:

$b^3 = \frac{2kl(q')^2}{mg}$

Подставим значение $q' = q/2$:

$b^3 = \frac{2kl(q/2)^2}{mg} = \frac{2klq^2}{4mg} = \frac{1}{4} \left( \frac{2klq^2}{mg} \right)$

Заметим, что выражение в скобках равно $a^3$ из уравнения (3). Таким образом:

$b^3 = \frac{a^3}{4}$

Отсюда находим новое расстояние $b$:

$b = \sqrt[3]{\frac{a^3}{4}} = \frac{a}{\sqrt[3]{4}}$

Подставим числовое значение $a = 9,5$ см:

$b = \frac{9,5 \text{ см}}{\sqrt[3]{4}} \approx \frac{9,5 \text{ см}}{1,5874} \approx 5,984 \text{ см}$

Округляя результат, получаем $b \approx 6$ см.

Ответ: После разрядки одного из шариков они притянутся, соприкоснутся, и заряд перераспределится поровну. Затем они оттолкнутся и установятся в новом положении равновесия на расстоянии $b = \frac{a}{\sqrt[3]{4}} \approx 6 \text{ см}$.

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