priyanka's Avatar
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19 Dec 2006 09:10:44 IST
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pendulum bob question [admin]: tention in charged pendulum
Engineering Entrance , Medical Entrance , NEET , JEE Main , AIIMS , JEE Main & Advanced , Physics , Electricity

a pendulum bob of mass 80mg and carrying a charge of 2*10-8 coulomb is at rest in a uniform horizontal electric field of 20kV/m.find
(a.)tension in the thread of the pendulum and
(b.)the angle it makes with the vertical.

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Nupur Goel's Avatar

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Joined: 13 Dec 2006
Posts: 666
19 Dec 2006 13:31:02 IST
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hey priyanka,
this problem can be solved by using the concept :
let  the  pendulum  makes  an  angle    with  the  vertical. Resolve the components of Tension  ' T '  in x-y directions..Tcos in vertical direction  and  Tsin  in  x direction.
Tcos  is  balanced  by  weight  mg  therefore,
Tcos = mg.....................................................(1)
Tsin  is  balanced  by  force F,
Tsin = F   ( where  F = qE  ).........................................(2)
by solving both the equations u will get the values of both tension as well as ....

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