Force can be defined as the physical cause that tends to change the resting position or uniform motion or to change the shape and size of the body. Force = ma M = mass of object a = acceleration of object in most of cases. Units of Force C.G.S. unit of force is 'dyne' and S.I. unit of force is 'newton' (N). Also we can consider SI unit of force is kg/m s -2 Force = ma = kg/m s -2 Absolute unit of force : If m = 1 unit, a = 1 unit, then the value of F = 1 unit Dyne : It is the force which when acting on a body of mass one gram produces in it an acceleration of 1 cm s -2 in its direction. Newton : It is the force which when acting on a body of mass 1 kg produces in it an acceleration of 1 m s -2 in its direction. Therefore 1 newton (N) = 1 kg × 1 m s -2