Номер 4, страница 103 - гдз по физике 9 класс учебник Шахмаев, Бунчук

Физика, 9 класс Учебник, авторы: Шахмаев Николай Михайлович, Бунчук Алексей Васильевич, издательство Мнемозина, Москва, 2007, голубого цвета

Авторы: Шахмаев Н. М., Бунчук А. В.

Тип: Учебник

Издательство: Мнемозина

Год издания: 2007 - 2026

Цвет обложки: голубой

ISBN: 978-5-346-01799-8

Глава 6. Силы в механике. Параграф 24. Центр масс - номер 4, страница 103.

App\Models\Task {#1030 // resources/views/models/task/default.blade.php
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  #table: "tasks"
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                    "field_recommended_books" => Illuminate\Database\Eloquent\Collection {#1100 …2}
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                    "field_cover_color" => Illuminate\Database\Eloquent\Collection {#1103 …2}
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                    "breadcrumbs" => array:3 [ …3]
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            "text" => "<p><strong>3.</strong> Что такое центр масс?</p><p>Центр масс (или центр инерции) — это точка, характеризующая распределение массы в теле или механической системе. Она обладает свойством, что движение этой точки представляет собой поступательное движение тела как единого целого. Если к телу приложить силу, то его центр масс будет двигаться так, как двигалась бы материальная точка, в которой сосредоточена вся масса тела и к которой приложена эта сила.</p><p>Положение центра масс является ключевым понятием в механике. Например, согласно второму закону Ньютона для системы тел, произведение полной массы системы на ускорение ее центра масс равно векторной сумме всех внешних сил, действующих на систему.</p><p>Для системы, состоящей из $\text{n}$ материальных точек с массами $m_1, m_2, \dots, m_n$ и радиус-векторами $\vec{r_1}, \vec{r_2}, \dots, \vec{r_n}$, радиус-вектор центра масс $\vec{r_c}$ определяется формулой: $$ \vec{r_c} = \frac{m_1\vec{r_1} + m_2\vec{r_2} + \dots + m_n\vec{r_n}}{m_1 + m_2 + \dots + m_n} = \frac{\sum_{i=1}^{n} m_i\vec{r_i}}{\sum_{i=1}^{n} m_i} $$</p><p>В однородном поле тяготения (например, вблизи поверхности Земли) центр масс совпадает с центром тяжести — точкой приложения равнодействующей силы тяжести.</p><p><strong>Ответ:</strong> Центр масс — это точка, которая характеризует распределение массы в теле (или системе тел) и движется так, как если бы в ней была сосредоточена вся масса системы и к ней были приложены все внешние силы, действующие на систему.</p><p><strong>4.</strong> Как опытным путем можно найти положение центра масс тела?</p><p>Положение центра масс тела можно определить экспериментально, используя его свойство совпадать с центром тяжести в однородном гравитационном поле. Самый распространенный метод — метод подвешивания, который особенно удобен для плоских тел произвольной формы.</p><p>Последовательность действий для плоского тела:<br>1. Сделать в теле (например, в плоской картонной фигуре) небольшое отверстие у края и подвесить его на гвоздь или иглу так, чтобы оно могло свободно вращаться.<br>2. После того как тело успокоится и придет в состояние равновесия, его центр масс окажется на вертикальной линии, проходящей через точку подвеса.<br>3. С помощью отвеса (нитки с грузом), также подвешенного к этой точке, прочертить на теле эту вертикальную линию.<br>4. Повторить процедуру, подвесив тело за другую точку, расположенную на достаточном удалении от первой.<br>5. Прочертить вторую вертикальную линию.<br>6. Точка пересечения двух проведенных линий и будет являться центром масс (центром тяжести) данного тела. Для повышения точности можно провести и третью линию, подвесив тело за третью точку.</p><p>Для объемных тел можно использовать метод балансировки. Тело уравновешивают на острие или ребре опоры. Когда тело находится в равновесии, его центр масс лежит на вертикали, проходящей через точку опоры. Найдя несколько таких вертикальных линий для разных положений тела, можно определить их точку пересечения, которая и является центром масс.</p><p><strong>Ответ:</strong> Положение центра масс тела можно найти опытным путем, например, методом подвешивания: тело подвешивают поочередно за две (или более) разные точки и каждый раз проводят вертикальную линию (с помощью отвеса) от точки подвеса вниз. Точка пересечения этих линий является искомым центром масс.</p>"
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            "text" => "<p><strong>3.</strong> Что такое центр масс?</p><p>Центр масс (или центр инерции) — это точка, характеризующая распределение массы в теле или механической системе. Она обладает свойством, что движение этой точки представляет собой поступательное движение тела как единого целого. Если к телу приложить силу, то его центр масс будет двигаться так, как двигалась бы материальная точка, в которой сосредоточена вся масса тела и к которой приложена эта сила.</p><p>Положение центра масс является ключевым понятием в механике. Например, согласно второму закону Ньютона для системы тел, произведение полной массы системы на ускорение ее центра масс равно векторной сумме всех внешних сил, действующих на систему.</p><p>Для системы, состоящей из $\text{n}$ материальных точек с массами $m_1, m_2, \dots, m_n$ и радиус-векторами $\vec{r_1}, \vec{r_2}, \dots, \vec{r_n}$, радиус-вектор центра масс $\vec{r_c}$ определяется формулой: $$ \vec{r_c} = \frac{m_1\vec{r_1} + m_2\vec{r_2} + \dots + m_n\vec{r_n}}{m_1 + m_2 + \dots + m_n} = \frac{\sum_{i=1}^{n} m_i\vec{r_i}}{\sum_{i=1}^{n} m_i} $$</p><p>В однородном поле тяготения (например, вблизи поверхности Земли) центр масс совпадает с центром тяжести — точкой приложения равнодействующей силы тяжести.</p><p><strong>Ответ:</strong> Центр масс — это точка, которая характеризует распределение массы в теле (или системе тел) и движется так, как если бы в ней была сосредоточена вся масса системы и к ней были приложены все внешние силы, действующие на систему.</p><p><strong>4.</strong> Как опытным путем можно найти положение центра масс тела?</p><p>Положение центра масс тела можно определить экспериментально, используя его свойство совпадать с центром тяжести в однородном гравитационном поле. Самый распространенный метод — метод подвешивания, который особенно удобен для плоских тел произвольной формы.</p><p>Последовательность действий для плоского тела:<br>1. Сделать в теле (например, в плоской картонной фигуре) небольшое отверстие у края и подвесить его на гвоздь или иглу так, чтобы оно могло свободно вращаться.<br>2. После того как тело успокоится и придет в состояние равновесия, его центр масс окажется на вертикальной линии, проходящей через точку подвеса.<br>3. С помощью отвеса (нитки с грузом), также подвешенного к этой точке, прочертить на теле эту вертикальную линию.<br>4. Повторить процедуру, подвесив тело за другую точку, расположенную на достаточном удалении от первой.<br>5. Прочертить вторую вертикальную линию.<br>6. Точка пересечения двух проведенных линий и будет являться центром масс (центром тяжести) данного тела. Для повышения точности можно провести и третью линию, подвесив тело за третью точку.</p><p>Для объемных тел можно использовать метод балансировки. Тело уравновешивают на острие или ребре опоры. Когда тело находится в равновесии, его центр масс лежит на вертикали, проходящей через точку опоры. Найдя несколько таких вертикальных линий для разных положений тела, можно определить их точку пересечения, которая и является центром масс.</p><p><strong>Ответ:</strong> Положение центра масс тела можно найти опытным путем, например, методом подвешивания: тело подвешивают поочередно за две (или более) разные точки и каждый раз проводят вертикальную линию (с помощью отвеса) от точки подвеса вниз. Точка пересечения этих линий является искомым центром масс.</p>"
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                    "field_name" => "Алексей"
                    "field_patronymic" => "Васильевич"
                    "field_surname_rp" => null
                  ]
                  #original: array:12 [
                    "id" => 3942
                    "created_at" => "2026-04-10 13:58:26"
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                    "name" => "Бунчук"
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                    "field_foreign_lang_patronymic" => null
                    "field_foreign_lang_surname" => null
                    "field_name" => "Алексей"
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                  ]
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                    0 => "*"
                  ]
                }
              ]
              #escapeWhenCastingToString: false
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            "field_author_foreign" => Illuminate\Database\Eloquent\Collection {#1203
              #items: []
              #escapeWhenCastingToString: false
            }
            "field_book_type" => Illuminate\Database\Eloquent\Collection {#1204
              #items: array:1 [
                0 => App\Models\Term {#1205
                  #connection: "mysql"
                  #table: "terms"
                  #primaryKey: "id"
                  #keyType: "int"
                  +incrementing: false
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                  #withCount: []
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                  #perPage: 15
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                  +wasRecentlyCreated: false
                  #escapeWhenCastingToString: false
                  #attributes: array:10 [
                    "id" => 6671
                    "created_at" => "2026-04-10 13:58:26"
                    "updated_at" => null
                    "name" => "Учебник"
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                    "field_cases" => array:6 [ …6]
                    "field_plural_form" => null
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                    "field_short_name_foreign" => null
                    "field_translit" => "uchebnik"
                  ]
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                    "created_at" => "2026-04-10 13:58:26"
                    "updated_at" => null
                    "name" => "Учебник"
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                    "field_cases" => array:6 [ …6]
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                    "field_translit" => "uchebnik"
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                    0 => "*"
                  ]
                }
              ]
              #escapeWhenCastingToString: false
            }
            "field_country" => Illuminate\Database\Eloquent\Collection {#1206
              #items: array:1 [
                0 => App\Models\Term {#1207
                  #connection: "mysql"
                  #table: "terms"
                  #primaryKey: "id"
                  #keyType: "int"
                  +incrementing: false
                  #with: []
                  #withCount: []
                  +preventsLazyLoading: false
                  #perPage: 15
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                  #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"
                  ]
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                    "id" => 9
                    "created_at" => "2026-04-10 13:58:26"
                    "updated_at" => null
                    "name" => "Россия"
                    "field_cases" => array:6 [ …6]
                    "field_translit" => "rossiya"
                  ]
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                  #attributeCastCache: []
                  #dateFormat: null
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                    0 => "*"
                  ]
                }
              ]
              #escapeWhenCastingToString: false
            }
            "field_city" => Illuminate\Database\Eloquent\Collection {#1208
              #items: array:1 [
                0 => App\Models\Term {#1209
                  #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"
                  ]
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                  #attributeCastCache: []
                  #dateFormat: null
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                  +timestamps: true
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                  #visible: []
                  #fillable: []
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                    0 => "*"
                  ]
                }
              ]
              #escapeWhenCastingToString: false
            }
            "field_series" => Illuminate\Database\Eloquent\Collection {#1210
              #items: []
              #escapeWhenCastingToString: false
            }
            "field_umk" => Illuminate\Database\Eloquent\Collection {#1211
              #items: []
              #escapeWhenCastingToString: false
            }
            "field_level_of_education" => Illuminate\Database\Eloquent\Collection {#1212
              #items: []
              #escapeWhenCastingToString: false
            }
            "field_standart_of_education" => Illuminate\Database\Eloquent\Collection {#1213
              #items: []
              #escapeWhenCastingToString: false
            }
            "field_publication_number" => "4"
            "field_publication_type" => Illuminate\Database\Eloquent\Collection {#1214
              #items: array:1 [
                0 => App\Models\Term {#1215
                  #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"
                  ]
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                  #attributeCastCache: []
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                    0 => "*"
                  ]
                }
              ]
              #escapeWhenCastingToString: false
            }
            "field_under_the_edition" => Illuminate\Database\Eloquent\Collection {#1216
              #items: []
              #escapeWhenCastingToString: false
            }
            "field_under_the_edition_degree" => null
            "field_cover_description" => null
            "field_publication_year" => "2007"
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            "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" => "362"
            "field_priority" => null
            "field_default_folder" => "/fizika_09/shahmaev-u/"
            "field_isbn" => "978-5-346-01799-8"
            "field_cover" => array:1 [
              0 => "/media/fizika_09/shahmaev-u/covers/cover1.webp?ts=1759080267"
            ]
            "field_cover_alts" => array:1 [
              0 => ""
            ]
            "field_covers" => array:1 [
              0 => array:4 [
                "path" => "/media/fizika_09/shahmaev-u/covers/cover1.webp?ts=1759080267"
                "alt" => ""
                "width" => "2294"
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              ]
            ]
            "field_popular_book" => "0"
            "field_recommended_books" => Illuminate\Database\Eloquent\Collection {#1217
              #items: []
              #escapeWhenCastingToString: false
            }
            "field_new_book" => Illuminate\Database\Eloquent\Collection {#1218
              #items: []
              #escapeWhenCastingToString: false
            }
            "field_old_book" => Illuminate\Database\Eloquent\Collection {#1219
              #items: []
              #escapeWhenCastingToString: false
            }
            "field_url" => "/9-klass/fizika/shahmaev-uchebnik"
            "field_cover_color" => Illuminate\Database\Eloquent\Collection {#1220
              #items: array:1 [
                0 => App\Models\Term {#1221
                  #connection: "mysql"
                  #table: "terms"
                  #primaryKey: "id"
                  #keyType: "int"
                  +incrementing: false
                  #with: []
                  #withCount: []
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                  #escapeWhenCastingToString: false
                  #attributes: array:6 [
                    "id" => 52
                    "created_at" => "2026-04-10 13:58:26"
                    "updated_at" => null
                    "name" => "голубой"
                    "field_cases" => array:6 [ …6]
                    "field_translit" => "goluboy"
                  ]
                  #original: array:6 [
                    "id" => 52
                    "created_at" => "2026-04-10 13:58:26"
                    "updated_at" => null
                    "name" => "голубой"
                    "field_cases" => array:6 [ …6]
                    "field_translit" => "goluboy"
                  ]
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                    0 => "*"
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            "field_metatags_title" => null
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            "breadcrumbs" => array:3 [
              "class" => 380
              "subject" => 556
              "class_subject" => 493
            ]
          ]
          #original: array:50 [
            "id" => 2906
            "created_at" => "2026-04-10 13:58:26"
            "updated_at" => null
            "field_tree_default_status" => "tasks"
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            "field_subject" => Illuminate\Database\Eloquent\Collection {#1176}
            "field_class" => Illuminate\Database\Eloquent\Collection {#1184}
            "field_publisher" => Illuminate\Database\Eloquent\Collection {#1178}
            "field_author" => Illuminate\Database\Eloquent\Collection {#1179}
            "field_author_foreign" => Illuminate\Database\Eloquent\Collection {#1203}
            "field_book_type" => Illuminate\Database\Eloquent\Collection {#1204}
            "field_country" => Illuminate\Database\Eloquent\Collection {#1206}
            "field_city" => Illuminate\Database\Eloquent\Collection {#1208}
            "field_series" => Illuminate\Database\Eloquent\Collection {#1210}
            "field_umk" => Illuminate\Database\Eloquent\Collection {#1211}
            "field_level_of_education" => Illuminate\Database\Eloquent\Collection {#1212}
            "field_standart_of_education" => Illuminate\Database\Eloquent\Collection {#1213}
            "field_publication_number" => "4"
            "field_publication_type" => Illuminate\Database\Eloquent\Collection {#1214}
            "field_under_the_edition" => Illuminate\Database\Eloquent\Collection {#1216}
            "field_under_the_edition_degree" => null
            "field_cover_description" => null
            "field_publication_year" => "2007"
            "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" => "362"
            "field_priority" => null
            "field_default_folder" => "/fizika_09/shahmaev-u/"
            "field_isbn" => "978-5-346-01799-8"
            "field_cover" => array:1 [
              0 => "/media/fizika_09/shahmaev-u/covers/cover1.webp?ts=1759080267"
            ]
            "field_cover_alts" => array:1 [
              0 => ""
            ]
            "field_covers" => array:1 [
              0 => array:4 [
                "path" => "/media/fizika_09/shahmaev-u/covers/cover1.webp?ts=1759080267"
                "alt" => ""
                "width" => "2294"
                "height" => "3039"
              ]
            ]
            "field_popular_book" => "0"
            "field_recommended_books" => Illuminate\Database\Eloquent\Collection {#1217}
            "field_new_book" => Illuminate\Database\Eloquent\Collection {#1218}
            "field_old_book" => Illuminate\Database\Eloquent\Collection {#1219}
            "field_url" => "/9-klass/fizika/shahmaev-uchebnik"
            "field_cover_color" => Illuminate\Database\Eloquent\Collection {#1220}
            "field_metatags_title" => null
            "field_metatags_description" => null
            "field_h1" => null
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            "breadcrumbs" => array:3 [
              "class" => 380
              "subject" => 556
              "class_subject" => 493
            ]
          ]
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          #dateFormat: null
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          #touches: []
          +timestamps: true
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          #visible: []
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            0 => "*"
          ]
        }
      ]
      #escapeWhenCastingToString: false
    }
    "page" => Illuminate\Database\Eloquent\Collection {#1229
      #items: array:1 [
        0 => App\Models\BookPage {#1228
          #connection: "mysql"
          #table: "book_pages"
          #primaryKey: "id"
          #keyType: "int"
          +incrementing: true
          #with: []
          #withCount: []
          +preventsLazyLoading: false
          #perPage: 15
          +exists: true
          +wasRecentlyCreated: false
          #escapeWhenCastingToString: false
          #attributes: array:21 [
            "id" => 1436662
            "created_at" => "2026-04-10 13:58:26"
            "updated_at" => null
            "field_page_start" => "103"
            "field_url" => "/9-klass/fizika/shahmaev-uchebnik/page-103"
            "field_display_title" => "103"
            "field_folder" => "1"
            "field_image_name" => "103"
            "field_branch_parent" => Illuminate\Database\Eloquent\Collection {#1230
              #items: []
              #escapeWhenCastingToString: false
            }
            "field_weight" => "0"
            "field_book_parent" => Illuminate\Database\Eloquent\Collection {#1231
              #items: array:1 [
                0 => App\Models\Book {#1182}
              ]
              #escapeWhenCastingToString: false
            }
            "field_metatags_title" => null
            "field_metatags_description" => null
            "field_h1" => null
            "field_description_top" => null
            "field_description_bottom" => null
            "edition_groups" => Illuminate\Database\Eloquent\Collection {#1232
              #items: []
              #escapeWhenCastingToString: false
            }
            "content" => Illuminate\Database\Eloquent\Collection {#1242
              #items: array:1 [
                0 => App\Models\Element {#1241
                  #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" => 1702738
                    "created_at" => "2026-04-10 13:58:26"
                    "updated_at" => null
                    "edition" => Illuminate\Database\Eloquent\Collection {#1243 …2}
                    "book_page" => array:2 [ …2]
                    "img" => array:1 [ …1]
                  ]
                  #original: array:6 [
                    "id" => 1702738
                    "created_at" => "2026-04-10 13:58:26"
                    "updated_at" => null
                    "edition" => Illuminate\Database\Eloquent\Collection {#1243 …2}
                    "book_page" => array:2 [ …2]
                    "img" => array:1 [ …1]
                  ]
                  #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
            }
            "next" => array:2 [
              "refs" => "1436663"
              "type" => "book_page"
            ]
            "previous" => array:2 [
              "refs" => "1436661"
              "type" => "book_page"
            ]
            "tasks" => Illuminate\Database\Eloquent\Collection {#1524
              #items: array:5 [
                0 => App\Models\Task {#1536
                  #connection: "mysql"
                  #table: "tasks"
                  #primaryKey: "id"
                  #keyType: "int"
                  +incrementing: true
                  #with: []
                  #withCount: []
                  +preventsLazyLoading: false
                  #perPage: 15
                  +exists: true
                  +wasRecentlyCreated: false
                  #escapeWhenCastingToString: false
                  #attributes: array:24 [
                    "id" => 1436996
                    "created_at" => "2026-04-10 13:58:26"
                    "updated_at" => null
                    "field_page_start" => "103"
                    "field_page_end" => null
                    "field_url" => "/9-klass/fizika/shahmaev-uchebnik/24-1"
                    "field_display_title" => "1"
                    "field_outside_task" => null
                    "field_task_type" => Illuminate\Database\Eloquent\Collection {#1537 …2}
                    "field_metatags_title" => null
                    "field_metatags_description" => null
                    "field_h1" => null
                    "field_description_top" => null
                    "field_description_bottom" => null
                    "field_match" => null
                    "breadcrumbs" => []
                    "edition_groups" => Illuminate\Database\Eloquent\Collection {#1538 …2}
                    "top_parent_branch" => Illuminate\Database\Eloquent\Collection {#1539 …2}
                    "parent_branches" => Illuminate\Database\Eloquent\Collection {#1540 …2}
                    "content" => Illuminate\Database\Eloquent\Collection {#1542 …2}
                    "next" => array:2 [ …2]
                    "previous" => array:2 [ …2]
                    "book" => Illuminate\Database\Eloquent\Collection {#1548 …2}
                    "page" => array:2 [ …2]
                  ]
                  #original: array:24 [
                    "id" => 1436996
                    "created_at" => "2026-04-10 13:58:26"
                    "updated_at" => null
                    "field_page_start" => "103"
                    "field_page_end" => null
                    "field_url" => "/9-klass/fizika/shahmaev-uchebnik/24-1"
                    "field_display_title" => "1"
                    "field_outside_task" => null
                    "field_task_type" => Illuminate\Database\Eloquent\Collection {#1537 …2}
                    "field_metatags_title" => null
                    "field_metatags_description" => null
                    "field_h1" => null
                    "field_description_top" => null
                    "field_description_bottom" => null
                    "field_match" => null
                    "breadcrumbs" => []
                    "edition_groups" => Illuminate\Database\Eloquent\Collection {#1538 …2}
                    "top_parent_branch" => Illuminate\Database\Eloquent\Collection {#1539 …2}
                    "parent_branches" => Illuminate\Database\Eloquent\Collection {#1540 …2}
                    "content" => Illuminate\Database\Eloquent\Collection {#1542 …2}
                    "next" => array:2 [ …2]
                    "previous" => array:2 [ …2]
                    "book" => Illuminate\Database\Eloquent\Collection {#1548 …2}
                    "page" => array:2 [ …2]
                  ]
                  #changes: []
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                  #classCastCache: []
                  #attributeCastCache: []
                  #dateFormat: null
                  #appends: []
                  #dispatchesEvents: []
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                  #relations: []
                  #touches: []
                  +timestamps: true
                  +usesUniqueIds: false
                  #hidden: []
                  #visible: []
                  #fillable: []
                  #guarded: array:1 [
                    0 => "*"
                  ]
                }
                1 => App\Models\Task {#1543
                  #connection: "mysql"
                  #table: "tasks"
                  #primaryKey: "id"
                  #keyType: "int"
                  +incrementing: true
                  #with: []
                  #withCount: []
                  +preventsLazyLoading: false
                  #perPage: 15
                  +exists: true
                  +wasRecentlyCreated: false
                  #escapeWhenCastingToString: false
                  #attributes: array:24 [
                    "id" => 1436997
                    "created_at" => "2026-04-10 13:58:26"
                    "updated_at" => null
                    "field_page_start" => "103"
                    "field_page_end" => null
                    "field_url" => "/9-klass/fizika/shahmaev-uchebnik/24-2"
                    "field_display_title" => "2"
                    "field_outside_task" => null
                    "field_task_type" => Illuminate\Database\Eloquent\Collection {#1541 …2}
                    "field_metatags_title" => null
                    "field_metatags_description" => null
                    "field_h1" => null
                    "field_description_top" => null
                    "field_description_bottom" => null
                    "field_match" => null
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№4 (с. 103)
Условие. №4 (с. 103)
скриншот условия
Физика, 9 класс Учебник, авторы: Шахмаев Николай Михайлович, Бунчук Алексей Васильевич, издательство Мнемозина, Москва, 2007, голубого цвета, страница 103, номер 4, Условие

4. Как опытным путем можно найти положение центра масс тела?

Решение. №4 (с. 103)

3. Что такое центр масс?

Центр масс (или центр инерции) — это точка, характеризующая распределение массы в теле или механической системе. Она обладает свойством, что движение этой точки представляет собой поступательное движение тела как единого целого. Если к телу приложить силу, то его центр масс будет двигаться так, как двигалась бы материальная точка, в которой сосредоточена вся масса тела и к которой приложена эта сила.

Положение центра масс является ключевым понятием в механике. Например, согласно второму закону Ньютона для системы тел, произведение полной массы системы на ускорение ее центра масс равно векторной сумме всех внешних сил, действующих на систему.

Для системы, состоящей из $\text{n}$ материальных точек с массами $m_1, m_2, \dots, m_n$ и радиус-векторами $\vec{r_1}, \vec{r_2}, \dots, \vec{r_n}$, радиус-вектор центра масс $\vec{r_c}$ определяется формулой: $$ \vec{r_c} = \frac{m_1\vec{r_1} + m_2\vec{r_2} + \dots + m_n\vec{r_n}}{m_1 + m_2 + \dots + m_n} = \frac{\sum_{i=1}^{n} m_i\vec{r_i}}{\sum_{i=1}^{n} m_i} $$

В однородном поле тяготения (например, вблизи поверхности Земли) центр масс совпадает с центром тяжести — точкой приложения равнодействующей силы тяжести.

Ответ: Центр масс — это точка, которая характеризует распределение массы в теле (или системе тел) и движется так, как если бы в ней была сосредоточена вся масса системы и к ней были приложены все внешние силы, действующие на систему.

4. Как опытным путем можно найти положение центра масс тела?

Положение центра масс тела можно определить экспериментально, используя его свойство совпадать с центром тяжести в однородном гравитационном поле. Самый распространенный метод — метод подвешивания, который особенно удобен для плоских тел произвольной формы.

Последовательность действий для плоского тела:
1. Сделать в теле (например, в плоской картонной фигуре) небольшое отверстие у края и подвесить его на гвоздь или иглу так, чтобы оно могло свободно вращаться.
2. После того как тело успокоится и придет в состояние равновесия, его центр масс окажется на вертикальной линии, проходящей через точку подвеса.
3. С помощью отвеса (нитки с грузом), также подвешенного к этой точке, прочертить на теле эту вертикальную линию.
4. Повторить процедуру, подвесив тело за другую точку, расположенную на достаточном удалении от первой.
5. Прочертить вторую вертикальную линию.
6. Точка пересечения двух проведенных линий и будет являться центром масс (центром тяжести) данного тела. Для повышения точности можно провести и третью линию, подвесив тело за третью точку.

Для объемных тел можно использовать метод балансировки. Тело уравновешивают на острие или ребре опоры. Когда тело находится в равновесии, его центр масс лежит на вертикали, проходящей через точку опоры. Найдя несколько таких вертикальных линий для разных положений тела, можно определить их точку пересечения, которая и является центром масс.

Ответ: Положение центра масс тела можно найти опытным путем, например, методом подвешивания: тело подвешивают поочередно за две (или более) разные точки и каждый раз проводят вертикальную линию (с помощью отвеса) от точки подвеса вниз. Точка пересечения этих линий является искомым центром масс.

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