Question

A body of mass 5 kg is moving with a momentum of 10 kg-m/s.A force of 0.2 N acts on it in the direction of motion of the body for 10 seconds. The increase in its kinetic energy is

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

Answer 1

The correct option is D

4.4 J

Change in momentum = $P_2-P_1=F\times t\Rightarrow P_2=P_1+F\times t=10+0.2\times 10=12kgm/s$

Increase in kinetic energy $E=\frac{1}{2m}[P_2^2-P_1^2]=\frac{1}{2m}\left[\right(12{)}^2-\left(10{)}^2\right]=\frac{1}{2\times 5}[144-100]=\frac{44}{10}=4.4J$