a weight hung from a fixed point so that it can swing freely. Used in clocks to help the mechanism keep time

a term that is often used to describe ways in which energy is wasted

move or cause to move back and forth or from side to side while suspended or on an axis

A force between 2 surface that are in contact and trying to move over each other

a substance applied between two moving surfaces to reduce the friction between them, improving efficiency and reducing wear