A 3.0 g ping pong ball is suspended from a thread 35 cm long. When a comb is brought to the same height, the ping pong ball is repelled and the thread makes an angle of 10.0o with the vertical. What is the electric force exerted on the ping pong ball?

Answer 1

m•g = T•sinα
F(el) =T•cosα
m•g/F(el) = sinα/cosα = tanα,
F(el) = m•g/tanα .