The sum of kinetic energy (K) and potential energy (U) is mechanical energy. If a rigid body has its CM at height hcm above gravitational zero level of potential energy,
U = mg hcm,
The mechanical energy (E) of rolling body will be
In other fields like spring force, other terms may apparel in the expression for U. If there be no sliding, the work done by friction force is zero. The mechanical energy *** conserved in that situation.
