Question

Give a specific example of a system with the energy transformation U-->delta Eth (U and Eth are the potential and the thermal energies of the system) Any energy not mentioned in the transformation is assumed to remain constant; if work is not mentioned it is assumed to be zero.

Answer 1

Consider spring mass system on horizontal rough floor. If we released the spring from its maximum compression or maximum extension, the spring oscillates about its mean position. Due to the surface is rough, the oscillations decrease and finally the block comes to rest. Now the total energy that is the sum of elastic potential energy and the kinetic energy of the system is zero. This is contradiction to the law of conservation of energy. Thus, the initial potential energy of the spring converts thermal energy as the surface is rough