In classical mechanics, for a body with constant mass, the acceleration of the body is proportional to the resultant (total) force acting on it (Newton's second law):
:<math>\mathbf{F} = m\mathbf{a} \quad \to \quad \mathbf{a} = \mathbf{F}/m</math>
where F is the resultant force acting on the body, m is the mass of the body, and a is its acceleration.