Question

While diving down if the diver folds himself compact, then his :
A) angular velocity increases
B) angular momentum decreases
C) rotational kinetic energy increases
D) moment of inertia decreases

• A. A, B and C are true
• B. B, C and D are true
• C. A, C and D are true
• D. A, B and D are true

Answer 1

The correct option is C A, C and D are true

Moment of inertia will decrease since the diver folds himself.
Angular momentum is conserved as no external torque is applied ,so
$L_1=L_2$
$I_1{\omega }_1=I_2{\omega }_2$
Since $I_2<I_1$, ${\omega }_1<{\omega }_2$
$K{E}_1=\frac{1}{2}{I}_1{\omega }_1^2=\frac{L_1^2}{2I_1}$
$K{E}_2=\frac{1}{2}{I}_2{\omega }_2^2=\frac{L_2^2}{2I_2}$
Since $I_2<I_1$ $K{E}_2>K{E}_1$