Answer :
When the object slides across the rough surface some of its potential energy will be lost to friction.
Conservation of mechanical energy
The law of conservation of mechanical energy states that the total mechanical energy of an isolated system is always constant.
M.A = P.E + K.E
When the object slides across the rough surface, some of the potential energy of the object will be converted into kinetic energy while the remaining potential energy will be converted into thermal energy due to frictional force of the rough surface.
P.E = K.E + thermal energy
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