Question

A solid sphere is rotating freely about its symmetry axis in free space. The radius of the sphere is increased keeping its mass same. Which of the following physical quantities would remain constant for the sphere ?

• A. Angular momentum
• B. Angular velocity
• C. Rotational kinetic energy
• D. Moment of inertia

Answer 1

Answer: (A)

Angular momentum

Answer 2

$\tau_{ex} = 0$
So, $\frac{dL}{dt} = 0$
i.e. $L =$ constant
So angular momentum remains constant.