Q24 of 28 Page 159

A porter with a suitcase on his head is climbing up steps with uniform speed. The work done by the “weight of the suitcase” on the suitcase is

(a) Positive


(b) Negative


(c) Zero


(d) Undefined

(b)

Explanation : work done is negative because , gravitational force is the cause of weight and it acts downward on suitcase and displacement is upward.


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22

Two bodies of unequal masses are dropped from the top of building. Which of the following is equal for both bodies at any instance?

(a) Speed


(b) force of gravity


(c) potential energy


(d) kinetic energy

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A man with a box on his head is climbing up a ladder. The work done by the man on the box is

(a) Positive


(b) Negative


(c) Zero


(d) Undefined.

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