A boy of mass m climbs up the stairs of vertical height h. (a) What is the work done by the boy against the force of gravity ? (b) What would have been the work done if he uses a lift in climbing the same vertical height ?

Explanation

To solve the problem step by step, we will address both parts of the question regarding the work done by the boy against the force of gravity when climbing stairs and using a lift.

### Part (a): Work Done by the Boy Against the Force of Gravity

1. **Identify the Mass and Height**: Let the mass of the boy be \( m \) and the vertical height he climbs be \( h \).

2. **Understand Work Done Against Gravity**: The work done against the force of gravity is equal to the change in potential energy of the boy. The potential energy (PE) at a height \( h \) is given by the formula:
\[
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