Find that greek thing..

AIEEE 2015 Help › Mechanics questions › Find that greek thing..

A simple pendulum consists of a bob of mass 'm' attached to a string of breaking strength double the weight of the bob. The bob is released from rest vertically when the string is horizontal. The string breaks when it makes an angle Î¸ with the vertical. Find Î¸.

a) cos^-1 1/3
b) cos^-1 2/3
c)60Â°
d)0Â°

#Physics #Mechanics

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4 Answers

1

ANKIT MAHATO ·2009-07-01 00:54:22

b) cos-1 2/3

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ANKIT MAHATO ·2009-07-01 00:57:59

energy conservation :

mgl = mgl(1 - cosÎ¸) + 1/2 m v²
m v² = 2mglcosÎ¸

force eq the string will break if the frce is 2mg

mgcosÎ¸ + m v²/l = 2mg
3mgcosÎ¸ = 2mg

cos Î¸ = 2/3

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Ritika ·2009-07-01 07:18:11

thx a lot.

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ANKIT MAHATO ·2009-07-02 22:14:56

welcome :)

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