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A ball is thrown vertically downwards from a height of 20 m with an initial velocity v0. It collides with the ground loses 50 percent of its energy in collision and rebounds to the same height. The initial velocity v0 is :
[2015 RS] (Take g = 10 ms–2)
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- 20 ms–1
- 28 ms–1
- 10 ms–1
- 14 ms–1
Correct Option: A
When ball collides with the ground it loses its 50% of energy
| ∴ | = | ⇒ | m1Vf2 | = | |||||
| 2 | |||||||||
| K.Ei | 2 | m2Vi2 | 2 | ||||||
| 2 | |||||||||
| or | = | ||
| Vi | √2 |
| or | = | ||
| √V0² + 2gh | √2 |
or, 4gh = V02 + 2gh
∴ V0 = 20 ms–1
