A body of mass 4 kg is moving with momentum of `8 kg m s^(-1)`. A force of 0.2 N acts on it in the direction of motion of the body for 10 s. The increase in kinetic energy is

Options

A. 10
B. 8.5
C. 4.5
D. 4

Answer

c

Explanation

Force `F=(p_(2)-p_(1))/t`
Force -rate of change of momentum
`0.2=mv-18/10`
`mv=2+8`
`v=10/4=5/2 m//s`
`p_(2) =mv=4x5/2=10kgm//s`
`Delta K.E= (p overset(2) underset(2)-poverset(2)underset(1)/2m=10^(2)-8^(2)/2xx4=36/8=4.5J`