Question

Which of the following cases shows work done by the force 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.

$\text{Work done}=\text{force}\times \text{displacement in the direction of force}$

In the first option, rahul is standing still. So the displacement is 0, the product of force and displacement reduces to zero. So work done is zero.

In the second option, Even on the application of force rock is not moving i.e. displacement of the rock is 0. So work done is zero.

In third case displacement is non-zero and force is also non-zero. So work done is non-zero.