Statics is one of the two branches of mechanics, the science that studies the effects of forces on bodies at rest or in motion. The other branch of mechanics is dynamics.
Statics deals with a body at rest, or in motion at a constant speed and in a constant direction. Such a body is said to be in equilibrium because the forces acting on it cancel each other out. Dynamics deals with bodies that change speed, direction, or both, because of forces acting on them.