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?

(a) 0.75 s 

(b) 1.33 s 

(c) 6 s 

(d) 35 s

Answer 1

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

u = 15 ms^-1

V = 0

t = ? 

v = u + at 

0 = 15 – 2.5t

t = \(\frac{15}{2.5}\) =6s