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A bird is sitting on the top of a vertical pole 20 m high and its elevations 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

`20sqrt2`

B

`20(sqrt3-1)`

C

`40(sqrt2-1)`

D

`40(sqrt3-sqrt2)`

Text Solution

Verified by Experts

The correct Answer is:
B
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