According to the law of conservation of energy, mechanical energy can be changed to heat energy.

The answer to this question is given below in this explanation section.

Explanation:

                     " law of conservation of energy"

The law of conservation of energy states that energy can neither be created nor destroyed only converted from one form of energy into another.This mean that a system always has a same account of a energy,unless it is added from the outside.This is particularly confusing in the case of non conversation forces,where energy is converted from ,mechanical energy into thermal energy.but the overall energy does remain the same.The only way to use energy is to transform energy from one form to another.

The amount of energy in any system than it is determined by the following equation.

Ut=Ui +W+Q

It is also possible to determined the change in internal energy of the system using the equation.

ΔU=W+Q

The mechanical energy of a system increases provided their is no loss of energy due to friction.The energy would transform to kinetic energy when the speed is increasing.Te mechanical energy of a system remain constant provided their is no loss of energy due to friction.

The law of conversation of energy which say that in a closed system total energy is conserved that is it constant.

KE1 + PE1=KE2+PE2