This gives another clue about friction. We have seen that friction acts to resist movement and that engineers have evolved methods to reduce the effect of friction. We can get some idea of what happens if we rub our hands together very quickly. This can be useful if our hands are cold but is not useful in machines, the heat is lost to the surroundings and is wasted. Not only that, as we rub our hands together small amount of skin are worn away, this might not be a problem for us as our bodies have a capacity for self-repair but with machines this isn't the case and wear and tear will damage the machine.
Friction is a measure of the force pressing the two objects together.
Friction produces heat Friction results in wear and tear.