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प्रश्न
State the condition when the work done by a force is positive. Explain with the help of examples.
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उत्तर
If the displacement of the body is in the direction of force, then work done is positive.
Hence, W= F × S
For example: A coolie does work on the load when he raises it up against the force of gravity. The force exerted by coolie (=mg) and displacement, both are in upward direction.
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संबंधित प्रश्न
A boy weighing 40 kgf climbs up a stair of 30 steps each 20 cm high in 4 minutes and a girl weighing 30 kgf does the same in 3 minutes. Compare:
- The work done by them.
- The power developed by them.
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When a body moves in a circular path, how much work is done by the body? Give reason.
(Hint: The body is acted upon by the centripetal force.)
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What are the S.I. and C.G.S units of work? How are they related? Establish the relationship.
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A boy weighing 350 N climbs up 30 steps, each 20 cm high in 1 minute, Calculate:
- the work done and
- power spent.
Name the force needed for circular motion. What is the direction of the force?
A man spends 7.4 kJ energy in displacing a body by 74 m in the direction in which he applies force, in 2.5 s. Calculate the power spent (in H.P) by the man.
What do you understand by work? Is work a scalar or a vector quantity?
