A body of mass `2kg` moving on a horizontal surface with an initial velocity of `4 ms^(-1)` comes to rest after `2` second. If one wants to keep this body moving on the same surface with a velocity of `4 ms^(-1)` the force required is

Options

A. 8 N
B. 4 N
C. zero
D. 2 N

Answer

B

Explanation

Retarding force `=-ma=-m(v-u)//t`
`=2(4-0)//2=4N`
:. To keep velcity uniform force required = opposing force
=4N