A man of mass \(m,\) standing at the bottom of the staircase, of height \(L,\) climbs it and stands at its top.
| (a) | work done by all forces on man is equal to the rise in potential energy \(mgL.\) |
| (b) | work done by all forces on man is zero. |
| (c) | work done by the gravitational force on man is \(mgL.\) |
| (d) | the reaction force from a step does no work because the point of the application of the force does not move while the force exists. |
Choose the correct option from the given ones:
| 1. | (a), (d) | 2. | (a), (c) |
| 3. | (b), (d) | 4. | (a), (b), (c) |
gravitation force on the man is \(-mgL\) and the work done by the man is \(mgL.\)
Thus, the total work done on the man is given by;
\(\Rightarrow W =-mgL+mgL =0\)
The reaction force from a step does no work because the point of application of the
force does not move while the force exists, is true since they lose contact, thus no net work is done.
Hence, option (3) is the correct answer.
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