Question

A 75.0 kg man pushes on a 500,000 kg wall for 250 s but it does not move.

Answer 1

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The work done in the given case is 0

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For calculating the work done by an object we apply the formula, that is ~

• $f \times s \times \cos( \theta)$

where f represents force applied, and s represents displacement.

but here, the displacement is zero since the wall didn't move at all, Therefore If we plug it's value as 0, we get

• $f = 0 \times s \times \cos( \theta)$

hence,

• $work \: done = 0$

Answer 2

Solution:

• Here, though the man is applying force on the wall, the work done is zero.
• This is because work is said to be done only when a force acting on a body produces motion in it in the direction of the force applied.
• Here, the man is trying to push the wall with a great force. He might fell exhausted after some time and say that he has done a lot of work.
• But in terms of physics, he has done no work because the force applied by the person has not produced any displacement. We know, work done = force × displacement. If displacement is zero, then work done is zero.

So therefore, we can conclude that the man hasn't done any work.

Hope it helps.

Do comment if you have any query.