A body of mass 5 kg is moving with a momentum of `10 kg ms^(-1)`. A force of 0.2 N acts on it in the direction of motion of body for 10 s. The increase in its kinetic energy is 

Options

A. 2.8 J
B. 3.2 J
C. 3.8 J
D. 4.4 J

Answer

D

Explanation

Initial kinetic energy = `(p_1^2)/(2m) = (10 xx 10)/(2 xx 5) = 10 J`
Impulse = `p_2 - p_1 = F xx t`
`:. p_2 - 10 = 0.2 xx 10 or p_2 = 12 kg ms^(-1)`
Final kinetic energy = `(p_2^2)/(2m) = (12xx 12)/(2 xx 5) = 14.4 J`
Increase in kinetic energy = `14.4 J - 10 J = 4.4 J`