Question

If the angular momentum of a rotating body is increased by 200%, then its kinetic energy of rotation will be increased by

• A. 400%
• B. 800%
• C. 200%
• D. 100%

Answer 1

Answer: (B)

800%

Answer 2

As $E = \frac { L ^ { 2 } } { 2 I }$ ⇒ $\frac { E _ { 2 } } { E _ { 1 } } = \left( \frac { L _ { 2 } } { L _ { 1 } } \right) ^ { 2 }$ $= \left( \frac { 3 L _ { 1 } } { L _ { 1 } } \right) ^ { 2 }$

[As = 3L₁]

⇒ $E _ { 2 } = 9 E _ { 1 }$ $= E _ { 1 } + 800 \%$ of $E _ { 1 }$