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5.Work, Energy, Power and Collision
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A stone tide 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 $\sqrt{ x \left( u ^{2}- gL \right)}$. The value of $x$ is .............
A
$3$
B
$2$
C
$1$
D
$5$
(JEE MAIN-2022)
Solution
$v =\sqrt{ u ^{2}-2 gL }$
$\Delta v =\sqrt{ u ^{2}+ v ^{2}}$
$\Delta v =\sqrt{ u ^{2}+ v ^{2}-2 gL }$
$\Delta v =\sqrt{2 u ^{2}-2 gL }$
$\Delta v =\sqrt{2\left( u ^{2}- gL \right)} x =2$
Standard 11
Physics
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