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A stone tied to a string of length L is whirled in a vertical circle with the other end of the string at the centre. At a certain instant of time, the stone is at its lowest position and has a speed u. The magnitude of change in its velocity, as it reaches a position where the string is horizontal, is gL 2 u ( x 2 − . The value of x is

1. 3
2. 2
3. 1
4. 5

Correct answer: 2

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