Suppose you lift a box from the ground over your head.You will be using energy as the work done.But when you keep the box lifted over your head are you using extra energy ???

When you lift the box to a desired height, say upwards to the head, you are in fact going against the gravitational force and hence doing work against gravity. This energy is stored in the box as gravitational potential energy.

However, while you are holding the box above your head there is no movement or displacement involved and we do not do any work. You might feel a pain on the hands since your muscles expend their energy in order to hold the box for long.

Regards,

Vasantha,

AskIITian Faculty,

MSc, B.Ed (CTTE College, Chennai)

According to laws of mechanics unless displacement is done ,no work. Hence no energy is being used