Q. If the angular momentum of a rotating body about a fixed axis is increased by $10\%$. Its kinetic energy will be increased by
A) 10%
B) 20%
C) 21%
D) 5%
Explanation
(c) $K = \frac{L^{2}}{2I} = \frac{K_{1}}{K_{2}} = \frac{L_{1}^{2}}{L_{2}^{2}} \Rightarrow \frac{K_{1}}{K_{2}} = \left( \frac{100}{110} \right)^{2} = \frac{100}{121}$
$\Rightarrow \frac{100}{K^{2}} = \frac{100}{121} \Rightarrow K_{2} = 121 = 100 + 21$
Increase in kinetic energy = 21%
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.