A point mass ' m " is moved in a vertical circle of radius 'r" with help of a stri

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5.Work, Energy, Power and Collision

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A point mass '$m$" is moved in a vertical circle of radius 'r" with the help of a string. The velocity of the mass is $\sqrt{7 gr }$ at the lowest point. The tension in the string at the lowest point is .......... $mg$

A

$1$

B

$6$

C

$7$

D

$8$

(NEET-2020)

Solution

$T – mg =\frac{ mv ^{2}}{ r }$

$T – mg =\frac{ m (7 gr )}{ r }$

$T =8 mg$

Standard 11

Physics

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