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प्रश्न
Work is a scalar quantity because it is a measure of transfer of energy without indicating any direction
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उत्तर
When the displacement of the body is in the direction opposite to that of the applied force,the work done is negative.
W = Fd cos 0 = Fd cos 180° = -Fd
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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.
Give an example when work done by the force of gravity acting on a body is zero even though the body gets displaced from its initial position.
What do you mean by a centrifugal force?
An engine does 54,000 J of work by exerting a force of 6000 N on it. What is the displacement in the direction of the force?
A boy takes 3 minutes to lift a 20 litre water bucket from a 20 m deep well, while his father does it in 2 minutes. Compare:
- the work, and
- power developed by them.
How is 1 kgf related to the SI unit of force?
A bullet fired against a window glass pane makes a hole in it without any cracks while a stone striking the same glass pane smashes it; explain with reason.
In the following case write yes, if the work is being done and no if no work is being done.
A man trying to push a wall.
Justify the statement. “Power can be expressed as the product of force and velocity.”
