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A ball is projected vertically down wit...

A ball is projected vertically down with an initial velocity from a height of `20 m` onto a horizontal floor. During the impact it loses `50%` of its energy and rebounds to the same height. The initial velocity of its projection is

A

`20 ms^(-1)`

B

`15 ms^(-1)`

C

`10 ms^(-1)`

D

`5 ms^(-1)`

Text Solution

Verified by Experts

The correct Answer is:
A
From energy conservation –
`[1/2 mv^2 + "mgh" ] xx50/100 = mgh`
`implies 1/sqrt2v^2 = gh implies v = sqrt(2gh) = sqrt(2xx10 xx20) = 20 m//s`
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