Question

Four men lift a $250kg$ box to a height of $1m$ and hold it without raising and lowering it. Is there any work being done while holding? Why do they get tired while holding it? $(g=10m{s}^{-2})$

Answer 1

In order to hold the box, men are applying a force which is opposite and equal to the gravitational force acting on the box. There is no work being done because there is no displacement as they hold it without raising and lowering it. While applying the force, muscular effort is involved. So, they get tired.