Question

The velocity of a body of mass 5 kg acted upon by a constant retarding force of 10 N reduces to half of its initial value in 2 seconds, then initial velocity of the body is 3 m/s o 8 m/s 12 m/s 14.5 m/​

Answer 1

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/s

2

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