Question

Potential energy is stored in the body if some work is done on it. Work done is best given by:

(a) dU = Fdrcosθ

(b) dU = Fdrsinθ

(c) dU = Fdrcotθ

(d) dU = Fdrdθ

This question was addressed to me in final exam.

This question is from Potential Energy topic in portion Principle of Virtual Work of Engineering Mechanics

Answer 1

The correct option is (a) dU = Fdrcosθ

For explanation I would say: The work is defined as the dot product of the force and the distance. This means that the work is done does depends upon the angle of the force. That is the angle which is being made by the force vector to the surface of action of the force.