Question

Which of the following cases shows work done is non-zero?

• A. Rahul is standing still with a 30 kg weight on his head for 5 hours.
• B. Rohan is working hard to push a huge rock but the rock does not move despite all the effort.
• C. Rohan climbs the staircase to go to the second floor.
• D. All of these.

Answer 1

The correct option is C

Rohan climbs the staircase to go to the second floor.

In the first case, since Rahul is standing still, the displacement is zero, and hence the product of force and displacement reduces to zero. The displacement in the second case is also zero since the position of rock remains the same. Hence work done in first two cases will be zero. In the third case, since the position of Rohan is changing, displacement is non-zero and force is also non-zero. So work done is non-zero.