Four men lift a 250 kg box to a height of 1 m and hold it without raising or lowering it. (i) How much work is done by men in lifting the box? (ii) How much work is done in just holding it? (Take `g=10ms^(-2)`).

Answer

(i) Work done is 2500 J
(ii) Work done is 0 (zero).

Explanation

Here, `m=250kg, h=1m, g=10ms^(-2)`.
Weight of the box = force = `mg=250xx10N`
`=2500N`
Work done = mgh = `2500Nxx1m`
`=2500Nm`
`=2500J`
(ii) When the box is just hold, there is no displacement.
`therefore` The work done is zero, even though the men get tired.