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

Options

A. `2.8` joules
B. `3.2` joules
C. `3.8` joules
D. `4.4` joules

Answer

D

Explanation

Change in momentum = forcc xx time
`P_(2)- P_(1) = F xxt = 0.2 xx10= 2`
`implies P_(2) = 2 + P_(1) = 2 + 10 = 12gk -m//s`
increase in K.E.
`(1)/(2m)(P_(2)^(2) - P_(1)^(2)) (1)/(2 xx 5) [(12)^(2) - (10^(2)]`
`= (44)/(10) = 4.4 J` .