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A bob of pendulum of length 2 m describes an are of a circle in a vertical plane. If the lension in the cord is $2.5$ times the weight of the bob for the position shown, find the velocity of the bobs at that position.

a) 6.22 m

b) 5.66 m

c) 4.20 m

d) 2.44 m


1 Answer

Let T be tension in the string
The bob has a centerpetal force $ \large\frac{mv^2}{l}$
$T-mg \cos \theta=\large\frac{mv^2}{l}$
$2 mg-mg \cos 30=\large\frac{mv^2}{2}$
$v=5.66 m/s$
Hence b is the correct answer
answered Aug 7, 2013 by meena.p
edited Jun 13, 2014 by lmohan717

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