Signs of positive work:
If the force and displacement are in the same direction,then positive work is done.
Work is a scalar quantity. If the displacement is in the direction of the applied force, then W is positive. On the other hand if the displacement produced is opposite to the direction of the applied force, then W is a negative quantity.
If the force F causes a displacement s at an angle q, then we have to consider the component of displacement along F.
A measure of energy transfer that occurs when an object is moved over a distance by an external force at least part of which is applied in the direction of the displacement. If the force is constant, work may be computed by multiplying the length of the path by the component of the force acting along the path. Work done on a body is accomplished not only by a displacement of the body as a whole from one place to another but also, for example, by compressing a gas, by rotating a shaft, and even by causing invisible motions of the particles within a body by an external magnetic force.
No work is done unless the object is displaced in some way and there is a component of the force along the path over which the object is moved. Holding a heavy object stationary does not transfer energy to it, because there is no displacement. Holding the end of a rope on which a heavy object is being swung around at constant speed in a circle does not transfer energy to the object, because the force is toward the center of the circle at a right angle to the displacement. No work is done in either case.