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?

Angular velocity

Moment of inertia

Angular momentum

Rotational Kinetic energy

Solution

Angular momentum

Angular momentum remains conserved until the torque acting on sphere remains zero. $τ_{e x} = 0$

$S o, \frac{d L}{d t} = 0$

i.e. L = constant

So angular momentum remains constant.

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