Question

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

• A. $2.8Joule$
• B. $3.2Joule$
• C. $3.8Joule$
• D. $4.4Joule$

Answer 1

The correct option is D $4.4Joule$

momentum $\left(p\right)=m\times u=10Kg\frac{m}{s}$\\

$p=5\times u=10$

$u=\frac{10}{5}=2\frac{m}{s}$

$F=m\times a=0.2N$

when the force applied on moving object

$F=5\times a=0.2$

$a=0.25=0.04m\times s^{-}2$

Newton's laws of motion we will find the new velocity (v) of the object

$v=u+a\times t$

$v=2+0.04\times 10=2.4m\times s^{-}1$

change in kinetic energy

$\Delta K.E=12m\times v^2-12m\times u^2$

$\Delta K.E=12\times m(v^2-u^2)$

$\Delta K.E=12\times 5\times ({2.4}^2-2^2)$

$\Delta K.E=0.5\times 5\times (5.76-4)=4.4J$

Increase in kinetic energy will be $4.4$ joules.