Question

Four men lift a 250 kg box to a height of 1 m and hold it without raising or lowering it.
(a) How much work is done by the men in lifting the box?
(b) How much work do they do in just holding it?​

Answer 1

Solution:

As per the given data,

• Mass of the box = 250 kg
• Height = 1 m
• Acceleration due to gravity = 9.8 m/s ²

$\sf{(a)}$

Work done by the men in order to lift the box will be equal to its potential energy.

⇒ W = mgh

⇒ W = 250 x 9.8 x 1

⇒ W = 2450 J

The work done by the men in order to lift the box is 2450 J.

(b)

No work is done just by holding the box as the displacement/distance covered by the box is zero.

⇒ W = mgh

⇒ W = 250 x 9.8 x 0

⇒ W = 0 J