If two charged bodies are connected by a string will the tension be F or 2F?(F is the force of repulsion between them)

Question

score 2 · Answer 1 · edited Nov 27 '16 at 16:16

If the electrostatic repulsive force is given by $$F=\frac{Q_1Q_2}{4\pi\epsilon_0r^2}$$ and you consider one body held back by the string, the force exerted by the string on the body will be $-F$ so that there is a zero total force on the body. Thus, according to Newton's 3rd law, at any cross section of the string the sum of the positive and negative force $F$ gives a zero total force $F_\textrm{tot}=F-F=0.$ Thus the tension in the string is simply the repulsive force $F$ between the bodies

score 0 · Answer 2 · answered Nov 27 '16 at 15:54

The tension will be F because supposing you only had one of the charged bodies, there would be no tension. You have to look at it as though it is pulling from one side, don't look at it from both perspectives. The tension is being produced from one side.

For more explanation and verification look here:

https://www.physicsforums.com/threads/find-tension-in-string-connecting-two-charged-spheres.696711/

https://www.quora.com/What-is-the-tension-on-string-connecting-two-charged-spheres

If two charged bodies are connected by a string will the tension be F or 2F?(F is the force of repulsion between them)

2 Answers2