Basic Definition of Force :-
Force may be defined as an agent which produces or tends to produce, destroy or tends to destroy the motion of a body. A force while acting on a body may
(a) change the motion of a body,
(b) retard the motion of a body,
(c) balance the forces already acting on a body, and
(d) give rise to the internal stresses in a body.
In order to determine the effects of a force acting on a body, we must know the following characteristics of a force:
(i) The magnitude of the force,
(ii) The line of action of the force,
(iii) The nature of the force, i.e. push or pull, and
(iv) The point at which the force is acting.