Question

A body of mass $5\, kg$ has momentum of $10\, kg\, m / s$. When a force of $0.2\, N$ is applied on it for $10$ seconds, what is the change in its kinetic energy?

• A. 1.1 J
• B. 2.2 J
• C. 3.3 J
• D. 4.4 J

Answer 1

Answer: (D)

4.4 J

Answer 2

$u=\frac{p}{m}=\frac{10}{5}=2 m/s, a=\frac{0.2}{5}m/s^{2}$ $v=u+at=2+\frac{0.2}{5}\times10=2.4 m/s.$ $\Delta K=\frac{1}{2}mv^{2}-\frac{1}{2}mu^{2}=\frac{1}{2}\times5\times\left(2.4\right)^{2}-\frac{1}{2}\times5\times2^{2}$ = 4.4 J.