The law of conservation of energy asserts that total energy remains constant in an isolated system. That is, energy cannot be generated or destroyed, but it may be transferred from one form to another. Frictional forces can dissipate energy, which raises the question of whether it violates the law of conservation of energy. No, it does not. When there is friction, energy is transferred from one form to another. There will be no energy loss. To illustrate this issue, consider the following scenario: two buses collide. The buses are no longer moving as a result of the collision. Where does all of this energy go? The solution is simple: the friction between buses and between buses and the road allows energy to be transferred from one form to another. You may be aware that when we rub our hands together, heat is produced; what occurs here is frictional energy converting to heat energy. This is what happens in bus accidents, where the energies can be changed to thermal energy, acoustic energy, or any other type of energy owing to friction and impact. So the energy we believed we had wasted was really converted to heat and sound. Bus collisions are not only noisy, but they also cause a lot of friction on the ground and in the bent metal. Both heat and sound are types of energy.
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Nature's exact rules cannot be broken. The law of conservation of energy is an example of such a law. Friction constantly resists relative motion between two surfaces in contact.