plzz solve

Two small equally charged spheres each of mass m are suspended from the same point by silk threads of length l. The distance between the spheres is x<<l . find the rate dq/dt with which the charge leaks off each sphere if their approach velocities varies as v=a/√x ,where a is a constant .

8 Answers

62
Lokesh Verma ·

This is an awesome question...

See try making a fbd first an then try to write

dF/dt in terms of Q (dq/dt)

Now you can try? (I know it will sound very tough)

11
mona100 ·

sir i am unable to get the relation.......

1
rupal jain ·

sir i tried the same...but i could not reach the ans...
the ans of this ques is...3/2a√1/2k(mg/l)

1
neil.dhruva ·

i think there is minor mistake in ans..

x/(2l) = Felec/mg

mgx/2l = kq2/x2

mgx3/2kl = q2

mgx3/2kl = q

now d/dt both sides

1
rupal jain ·

ya i tried by this method...
by this method the ans in terms of √x
but this is not the ans... can u try again plzzzz

1
Surbhi Shah ·

i think there is a problem in x/2l= Fele/mg
it must be x/2l=(Fele-mA)/mg where A Is the acceleration

1
neil.dhruva ·

dx/dt = a/√x

therefore √x gets cancelled

1
rupal jain ·

ya i missed that...a real big mistake

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