Question

Explain if angular momentum and rotational kinetic energy can be conserved in a system whose moment of inertia is decreased.

Answer 1

 if angular momentum is conserved in a system whose moment of inertia is decreased ,then rotational kinetic energy will not be  conserved.

Explanation :
Angular momentum=L=Iω
where  I =moment of inertia
ω=angular momentum.

Kinetic energy of rotation=K.E=1/2 Iω²

K=I²w²/2I as L is constant

K is inversely proportional to I

Kα 1/I
So when moment of inertia decreases, K.E of rotation increases.Thus K.E of rotation is not conserved.

Answer 2

if angular momentum is conserved in a system whose moment of inertia is decreased, then total kinetic energy will not bebe also conserved