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ssbrightstar1

A particle having a charge 2.0 x 10^-4 C is placed directly

below and at a separation of 10 cm from the bob of a simple

pendulam at rest.The mass of the bob is 100 g.What charge

should the bob be given so that the string becomes loose?

Conjurer

T of the string < Force due to charge. T = mg here.

jinu.coolboy

To lose the string,upward force shold be equal to downward force.
i.e mg=K(2*10^-4)q/(0.1)^2 [q= charge on the bob]
0.1*10=(2*10^-4)q/(0.1)^2

calculate q from the above expression.I think it is nearly about 5.5*10^5 coulomb

chinmay_saxena01

the answer given by jinu.coolboy is correct
for string to be loose the downward force mg should be equal to upward force i.e. electrostatic force b/w bob and charged particle....let the charge of bob be q and after this solve the eqn.
K(2*10^-4)q/(0.1)^2 = mg

aryan123

5.5 *10^-5 C

+ve charge

using

repulsive force between bob n charge = weight of bob

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A particle having a charge 2.0 x 10-4 C is placed directly

below and at a separation of 10 cm from the bob of a simple

pendulam at rest.The mass of the bob is 100 g.What charge

should the bob be given so that the string becomes loose?

A particle having a charge 2.0 x 10^-4 C is placed directly