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A man of mass m , standing at the bottom...

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

The bullet will move in a different parabolic path

D

The reaction from a step does not do work because the point of application of the forces does not move while the force exists .

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Verified by Experts

The correct Answer is:
B, D
When a man of mass m climbs up the staircase of height L , work done by the gravitational force on the man is mgL work done by internal muscular forces will be -mgL as the change in kinetic energy is almost zero.
As the point on which conatct forces are applied does not move hence work done by reaction forces will be zero .
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