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प्रश्न
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उत्तर
K .E, K = `1/2` mv²
If speed is doubled
K.E, K' = `1/2` m (2v2)
or K' = 4 x `1/2` mv2 = 4K
Thus K.E becomes four times.
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संबंधित प्रश्न
Write an expression for the work done when a force is acting on an object in the direction of its displacement.
Express joule in terms of erg.
Choose one or more correct alternatives.
Joule is the unit of ______.
- force
- work
- power
- energy
A man carrying a suitcase in his hand is walking horizontally. What is the work done against gravity?
A boy of mass m climbs up a staircase of vertical height h.
- What is the work done by the boy against the force of gravity?
- What would have been the work done if he uses a lift in climbing the same vertical height?
A block of mass 20 kg is pulled up a slope (fig.12) with a constant speed by applying a force of 500 N parallel to the slope. A and B are initial and final positions of the block.
(a) Calculate the work done by the force in moving the block from A and B.
(b) Calculate the potential energy gained by the block.
How fast should a boy weighting 30 kg run so that his kinetic energy is 375 joule?
Mention whether work is done or not in the following activity.
| S. No | Activity | Work done or not done |
| 1. | Pushing the door | |
| 2. | Holding a doll | |
| 3. | Sitting in a bus | |
| 4. | Pushing a wall | |
| 5. | Digging soil |
