1)металлический шар массой 500 г падает на землю с высоты 3 м. какую работу при этом совершает сила тяжести?

1) g-постоянная величина = 9,8 или приблизительно равна 10

Переведем все данные значения в СИ:  500г= 0,5кг 

А=Fтяжести * S

Fтяжести = m * g =0.5 * 10=5 (Н)

А= 5 * 3 = 15 (Дж)

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Объяснение:

12,25 А (при g = 9,8 Н/кг)

или 12,5 А (при g = 10 Н/кг)

Объяснение:

Полезная работа: Ап = mgh

Затраченная работа или энергия, потреблённая электродвигателем:

Аз = Ап / КПД = mgh / КПД

Эта работа (Аз) была совершена электродвигателем. Её можно посчитать по формуле:

Аз = UIt, где U - напряжение, I - сила тока, t - время

Получаем:

U × I × t = m × g × h / КПД

Выразим силу тока:

I = m × g × h / (КПД × U × t)

I = 1000 кг × 9,8 Н/кг × 19 м / (0,8 × 380 В × 50 с) = 12,25 А

(если g принять за 10 Н/кг, то получим 12,5 А)