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A bird is sitting on the top of a vertical pole 20 m high and its elevation from a point 'O' on the ground is `45^(@)`. It flies off horizontally straight away from the point 'O'. After one second, the elevation of the bird from 'O' is reduced to `30^(@)`. Then the speed (in m/s) of the bird is

A

`40( sqrt(2)-1)`

B

`40( sqrt(3)-sqrt(2))`

C

`20 sqrt(2)`

D

`20(sqrt(3)-1)`

Text Solution

Verified by Experts

The correct Answer is:
D
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