A metallic solid sphere of radius R and mass m is rotating about a smooth spindle through its centre. Now the sphere is heated. then its kinetic energy of rotation

Due to thermal expansion, radius of the sphere increases. As a result its moment of inertia increases. Since no external torque is acting on the sphere, its angular momentum L remains unchanged.Now, K.E. of rotation =L22I . As I increases, K.E. decreases.