(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

A small 2g plastic ball is suspended by a 20 cm long string in a uniform electric field. If the ball is in equilibrium when the string makes a 15 degree angle with the vertical as indicated, what is the net charge on the ball?

Here's the diagram:

http://img295.imageshack.us/img295/7931/prob50diagramsk2.th.png [Broken]

2. Relevant equations

Coulumb's Law of electric force equation. F=kq1q2/r^2

Electric force equations. F=qE

3. The attempt at a solution

First I drew a FBD of the ball and the forces acting on it.

http://img164.imageshack.us/img164/3921/prob50fbdzy9.th.png [Broken]

Did I draw it correctly? I just want to confirm this first. There are only 2 x direction forces acting on it correct? The F_e is equal to q*E?? E being the electric force?

So do I just make T_x=qE and solve for the q? I don't get what they mean by net charge on the ball. Thanks! =D

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# Electric Field & Coulomb's Law Problem

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