# Homework Help: Charge over an Insulating Plate

1. Mar 5, 2012

### AJDangles

1. The problem statement, all variables and given/known data

Charge is distributed uniformly over the surface of a very large thin
insulating plate to a density of 5.00 x 10–6 C/m2 . An insulating string
connects a tiny charged bob to the vertical plate as shown in the
diagram. If the mass of the object is .001 g and the string makes an
angle of 30o to the plate, how much charge is carried by the bob?

2. Relevant equations

I have no clue.

3. The attempt at a solution

No idea where I should start. Can someone point me in the right direction?

2. Mar 5, 2012

### SammyS

Staff Emeritus
First explain where the string is attached to the plate.

Better yet, post an image of the diagram.

3. Mar 5, 2012

### AJDangles

Diagram here:

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4. Mar 5, 2012

### SammyS

Staff Emeritus
What is the Electric field near the surface of the plate?

5. Mar 5, 2012

### AJDangles

Take the force of gravity times a component of the angle, multiply by the charge of a proton?