A block of mass m at end of a string is whirled round in a vertical circle of radius R . critical sp

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5.Work, Energy, Power and Collision

easy

A block of mass $m$ at the end of a string is whirled round in a vertical circle of radius $R$. The critical speed of the block at the top of its swing below which the string would slacken before the block reaches the top is

A

$Rg$

B

${(Rg)^2}$

C

$R/g$

D

$\sqrt {Rg} $

Solution

(d) At highest point $\frac{{m{v^2}}}{R} = mg$

$⇒$ $v = \sqrt {gR} $

Standard 11

Physics

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