A stone tied to a string $L$ 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 as its lowest position and has a speed $u$. the magnitude of the change in its velocity as it reaches a position where the string is horizontal is
A stone tied to a string $L$ 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 as its lowest position and has a speed $u$. the magnitude of the change in its velocity as it reaches a position where the string is horizontal is
- A
$\sqrt {{u^2} - 2gL} $
- B
$\sqrt {2gL} $
- C
$\sqrt {{u^2} - gL} $
- D
$\sqrt {2\left( {{u^2} - gL} \right)} $
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