# Homework Help: Finding Q(point charge) with an angle, mass, and radii only

1. Apr 29, 2010

### Sakuraba_Neku

1. The problem statement, all variables and given/known data
To find the amount of static charge on the balls using coulomb's law and the concepts of equilibrium.

r = 3.3 cm
m1 = .085g
m2 = .085g
$$\vartheta$$ = 9.4$$\circ$$

2. Relevant equations

F = K(q1)(q2)\r2

3. The attempt at a solution
I legitimately have no clue how to do this other than the fact that r = 9.4...
Any tips/help will be appreciated.

2. Apr 29, 2010

### Superstring

If you could post the actual question it would be helpful. You simply can't solve that with the information you provided.

3. Apr 29, 2010

### Sakuraba_Neku

Sorry...but it's a lab so we don't have an actual question and we apparently have all the data we need. to solve for q.

We have a hint that states, "Remember the key to solving the lab lies in figuring out the x and y vectors."

I'm assuming parts of the vector is composed of gravity, tension, and the electric field which separated the balls from each other.

4. Apr 29, 2010

### ideasrule

Let me guess: this lab involves hanging two balls side by side from a common pivot point, and measuring the angle that the strings make at the pivot. Yes? If so, start by drawing a free-body diagram for one ball, then writing out Newton's second law for both x and y directions.

5. Apr 29, 2010

### Sakuraba_Neku

Yeah, that is exactly the lab we did. Thank you very much! I love this forum now.