Question

,Two pith-balls each wieghing 10-3 kg are suspended from the same point by means of silk thread 0.5 m long. On charging the pith balls equally, they found to repel each other to distance of 0.2 m .Calculate the charge on each ball?​

Answer 1

According to the fig.

force of repulsion is balanced by the sin component of the tension in the string.

F = Tsinθ

Weight is balanced by the cos component of the tension.

mg = Tcosθ

Fmg = tanθ

F = mg tanθ

sinθ = 0.10.5

sinθ = 1/5

cos θ = 2425

secθ = 2524

tanθ = 0.2

F = 1.96×10−3 N

F= kq2/r2

q2 = Fr2/k = 1.96×10−3×0.2×0.2/9×10^9

q = 0.9 μC