A constant retarding force of 80 N is applied to a body of mass 50 kg which is moving initially with a speed of 20 m/s. What would be the time required by the body to come to rest ?

Options

A. 15s
B. 14s
C. 12.5s
D. 18s

Answer

C

Explanation

Here retarding force F=80N
Mass of the body m=50kg
Initial speed of the body `u=20m//s`
As retarding force=mass `times` retardation
`therefore` Retardation `=F/m=(80N)/(50 kg)=1.6 m//s^2`
Let t be time required by the body to come to rest.
`therefore t=(v-u)/a=(0-20)/(-1.6)=12.5s`