Answer to Question #79589 in Mechanics | Relativity for hamid

Question

AS work is a scalar quantity then why it depends on direction?

Answer 1

One good way of distinguishing vectors from scalars is : Can you have a another vector equal in magnitude but opposite in direction such that the two add to zero.
If we apply this question to mechanical work, this would mean the following:
If a force F acts over a displacement S and thus perfoms mechanical work equal to F.s, would it be possible for a force of the same magnitude F now acting over a displacement of -S, thereby resulting in zero work?
It doesnt make sense. Work doesnt get undone by reversing the direction. Displacement does get undone, force does get cancelled.
The reason is that the basis for defining the concept of mechanical work is energy, and energy is a scalar, independent of direction. True, energy can either be accumulated or expended, but that has nothing to do with direction.