Question

Work done is best given by _____________

(a) dU = F.dr

(b) dU = Fdrsinθ

(c) dU = F.drcotθ

(d) dU = Fxdrdθ

I had been asked this question by my school principal while I was bunking the class.

I want to ask this question from Work in section Principle of Virtual Work of Engineering Mechanics

Answer 1

Correct answer is (a) dU = F.dr

To explain: The work is defined as the dot product of the force and the distance. This means that the work 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.