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?
Retarding force, F=50N
Mass of the body, m=20kg
Initial velocity of the body, u=15m/s
Final velocity of the body, v=0
Using Newtons second law of motion, the acceleration (
a) produced is given by:
F=ma
50=20 ×a
a=−50/20=−2.5m/s2
Using the first equation of motion, the time (t) taken by the body to come at rest
v=u+at
t=−u/a=−15/−2.5=6s