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## Homework Statement

As indicated in the diagram, consider a rail inclined at an angle θ relative to the horizontal axis. A sphere (A) with a charge +q is fixed at the bottom of the rail. A second sphere (B) with a charge +2q and a mass (m) is free to move along the rail. The sphere (C), initially neutral (Q=0) is fixed above the rail, at a distance (L) from the sphere (A).

1. Determine the equilibrium distance (d) between the spheres A and B.

2. What charge, Q, is needed on sphere C in order to move the sphere B upwards with an initial acceleration, a[itex]_{0}[/itex]

## Homework Equations

Coulombs law: F=[itex]\frac{kq_{1}q_{2}}{r^{2}}[/itex]

## The Attempt at a Solution

1. It seems like the equilibrium distance would be halfway between spheres A & C, but I think I'm missing something. Because sphere B is mobile, do I need to take into account the force of gravity acting on the sphere?

2. I think that in order to make sphere B move upwards, one would have to place the same charge on C as A, i.e Q[itex]_{C}[/itex]=+q, but given that C is placed higher than A, perhaps this changes?

As mentioned in a previous thread, my knowledge of physics is very elementary. Before this class, I had

**never**taken a physics course and the last math course I had was very basic. I need very clear, precise and elementary explications: i.e as you would give to a child, because this is honestly not my strong suit. I don't have a strong mathematical background either, so again, easy, clear explanations (when possible) are best. I apologize if the question is worded rather strangely; it was translated from my homework which is in French, so if something seems unclear, I will do my best to explain it.