# Two Electric Charges- Electric Force-Ranking

1. Dec 3, 2011

### jeandempsey

1. The problem statement, all variables and given/known data
Below are seven arrangements of two electric charges. All of the charges are the same size, 20 C, but they are either positive or negative. Each figure also has a point labeled P that lies on a straight line with the two charges. The distance between any two items is all 5 cm. There are no other charges in this region. A +5 C charge is placed at point P. Rank the strength (magnitude only) of the electric force on the +5 C charge when it is placed at point P from greatest to least.

2. Relevant equations
Fe= k(q1q2)/r^2

3. The attempt at a solution
help get me started please? :) I don't know how to get started.

Last edited: Dec 3, 2011
2. Dec 3, 2011

### ehild

What do you mean by that? Is 5 cm the distance from P of both the + and - charges?

ehild

3. Dec 3, 2011

### jeandempsey

between any two items is 5 cm. For example, in C,
between - and P it is 5 cm and between P and + it is 5 cm.

4. Dec 3, 2011

### ehild

And what is the distance between + and - in B?
Anyway, the + and - charges are of the same in magnitude, so what about the force they exert on the charge at P if the distances are equal? What about the direction the forces? Draw the forces with arrows in the pictures, and determine the resultant.

ehild

5. Dec 3, 2011

### jeandempsey

Oh! I think I understand it now. Thank you

6. Dec 3, 2011

### SammyS

Staff Emeritus
Hi jeandempsey. Welcome to PF.

Would you like to give your answers & your reasoning so that ehild or one of our other homework helpers can check that you really do understand this.