Question

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

Answer 1

Given: m = 20 kg, u = 15ms^-1, v = 0,

F = – 50 N (retarding force)

To find: Time (t)

Formula: v = u + at

Calculation: Since, F = ma

∴ a = \(\frac{F}{m}=\frac{50}{20}\) = -2.5 m s^-2

From formula,

0 = 15 + (-2.5) × t

∴ t = 6s

Time taken to stop the body is 6 s.