# Question #1b820

Feb 20, 2015

The law of conservation of energy states that the total energy of an isolated system remains constant during time.

So if you calculate the amount of energy before (${E}_{b}$) the motion, in presence of friction, you can notice that after the motion the energy will be less (${E}_{a}$), because some energy is emitted in heat.

The energy emitted from an object due to friction is:

${E}_{e} = {E}_{b} - {E}_{a}$.