Q145 / 160 · WBJEE 2010 · Physics
If momentum is increased by $20 \%$, then kinetic energy increases by
- A$48 \%$
- Correct answerB$44 \%$
- C$40 \%$
- D$36 \%$
Solution
Hints: $\mathrm{K}=\frac{\mathrm{P}^2}{2 m}$
Here $\mathrm{P}^{\prime}=1.2 \mathrm{P}$
Hence, $K^{\prime}=\frac{(1.2 \mathrm{P})^2}{2 m}$
$$
\mathrm{K}^{\prime}=1.44 \frac{\mathrm{P}^2}{2 m}
$$
$\mathrm{K}^{\prime}=1.44 \mathrm{~K}$ or Percentage increase in $\mathrm{K}=44 \%$
Hence, the correct answer is option: 'B'.