Find Tension in String Connecting Two Charged Spheres

[vex390]

Two charged objects of charge q.

Coulomb's law states that the force on one sphere by the field of the other is:

F = qE

But each sphere experiences that, correct? So the tension for the string would be 2F. Is that correct?

 

[rude man]

No.

Take one of the spheres and write sum of forces on it = 0 (since the sphere is not accelerating).
.

 

[Redbelly98]

Welcome to PF.

Let's think about this. Each charged sphere has two forces exerted on it. Some questions to help you think about the situation:

1. What are the two forces acting on one of the spheres? (Take the sphere on the left, for example). Obviously one of the forces is the electric force as given by Coulomb's law, so this question is really asking you to identify another force that acts on a sphere.

2. What is the acceleration of that sphere -- and therefore ...

3. What is the net force acting on that sphere?

 

[vex390]

Well there's the force of the first particle1 onto the particle2 and then there's the equal and opposite reaction from particle 2's force onto particle 1.

 

[haruspex]

Well there's the force of the first particle1 onto the particle2 and then there's the equal and opposite reaction from particle 2's force onto particle 1.

No, you're still trying to look at it from both perspectives at once. Concentrate on the forces to which one sphere is subjected. That's both electrostatic force and tension.