Friction is the force that opposes the relative motion or tendency to such motion of two bodies in contact. If we try to push a block of wood across a table, there are two opposing forces that act: the force associated with the push, and a force that is associated with the friction which acts in the opposite direction. As frictional forces are decreased (for example, by placing oil on the table) the object moves further and further before stopping. This demonstrates Galileo’s law of inertia too.