Завдання 11 з 51 З прогулянкового катера, що рухався за течією річки, упав у воду надувний матрац. Через 10 хвилин після падіння матраца була помічена його відсутність. Одразу після цього катер змінив курс на зворотний і наздогнав матрац на відстані 1 км нижче за течією від місця, де матрац упав у воду. Визначте (у кілометрах за годину) швидкість течії річки, вважаючи, що модуль швидкості руху катера в обох напрямках однаковий.
Объяснение:
Дано:
m = 200 грамм = 0,2 килограмм - масса шара;
v1 = 7 м/с - скорость шара до удара об стену;
v2 = 6,25 м/с - скорость шара после удара об стену.
Требуется найти изменение импульса шара.
Импульс шара до удара об стену:
P1 = m * v1 = 0,2 * 7= 1,4кг * м / с;
Импульс шара после удара об стену:
P2 = m * -v2 = 0,2* -6,25= -1,25 кг * м / с - знак минуса взят потому что, что после удара об стену шар движется в противоположном направлении.
P2 - P1 = -1,25 - 1,4 = - 2,65 кг * м / с.
ответ: изменение импульса равно -2,65 кг * м / с
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