Question

constant retarding force of 50 N is applied to a body of mass 20 kg moving initially with a speed of 15 m s-1. How long does the body take to stop?

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Answer 1

F= ma

$5 0 = 20 \times a \\ a = \frac{5}{2 } = 2.5 \: m {s}^{ - 2}$

$v = u + a t \\ 0 = 15 + ( - 2.5) \times {t}\\ 15 - 2.5 {t} = 0 \\ 15 = \frac{5}{2} {t} \\ 3 \times 2 = {t} \\ t = 6 sec$