A bodu of mass `4kg` is moving with momentant 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. `10 J`
B. `0.5 J`
C. `4.5 J`
D. `4 J`

Answer

C

Explanation

Momentum + mass `xx` velocity `rArr = mu`
or `u = (p)/(m) = (5kg ms^(-1))/(4kg) = 2 ms^(-1)`
Acceleration `= (Force)/(Mass)`
`a = (0.2 N)/(4kg) = 0.05 ms^(-1)`
Distance travelled the body in `10s` is
`d = ut +(1)/(2)at^(2)`
`= (2ms^(-1)) (10s) = (1)/(2) (0.05ms^(-2))(10s)^(2)`
`= 20 m = 2.5m = 22.5m M`
Work done `W = Fd = (0.2N)(22.5m) = 4.5J`
According to work energy therem increases is kinetic energy = Work done `= 4.5 J`