Question

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%

Answer 1

The correct option is B 20%

Given,

$\frac{\Delta L}{L}=10$%

The expression for the rotational kinetic energy in terms of angular momentum,

$K=\frac{L^2}{2I}$. . . . . . .(1)

where, $L=$ angular momentum,

$I=$ moment of inertia

$K=$ rotational kinetic energy

From equation (1),

$\frac{\Delta K}{K}=2\frac{\Delta L}{L}$

$\frac{\Delta K}{K}=2\times 10=20$%

The correct option is B.