one of the three laws of motionformulated by Sir Issac Newton. It states that a force acting upon a body causes the body to accelerate in the direction of the force, the acceleration being directly proportional to the force and inversely proportional to the mass of the body. For example, a bicycle with one person on it will accelerate in direct proportion to the amount of force exerted on it and will decrease itsacceleration when more mass, such as a passenger, is added to it, thus requiring more force be exerted in order to increase the acceleration. See also Newton in this glossary.—Perception of Truth Approved Glossary (9 June 92)