There are two charges with charge q and mass m

[Abhishek Das]

There are two charges with charge q and mass m and they are in equilibrium. Then, in the diagram why is my teacher saying that electrostatic force(F)=mg? Below is diagram.

 

[TSny]

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OK, you've started with a diagram that correctly shows the gravity force and the electric force. It might help to also show any other forces acting on the particle.

What does "equilibrium" mean in terms of the forces?

 

[Abhishek Das]

Equilibrium means net force is zero, right?

 

[TSny]

Equilibrium means net force is zero, right?

Yes. That's right. If you added (head-to-tail) the force vectors acting on the particle, what would the diagram look like?