# Homework Help: About coulomb's law

1. Aug 4, 2004

### jazzchan

Dear all...

i have a question about coulomb's law as follows:

if there are three point charges are placed at the x-axis, first is +C, second is -C and the last one also is -C.

How could i know the direction of the force at the second and third one ??

best regards.

jazz

2. Aug 4, 2004

### Staff: Mentor

You'll have to be more specific: where are the charges? I assume you need to find the forces that these charges exert on each other? Remember that like charges (same sign) repel and unlike charges attract.

3. Aug 4, 2004

### jazzchan

Dear Doc Al

what is meaning of repel ??

if there is two postive charge at the X axis, one is 5C at x = 0, other is 6C at x = 40,
so what is the force direction ?? positve or negative ??

thanks

jazz

4. Aug 4, 2004

### Staff: Mentor

Repel means push away. Attract means pull together.
I assume you are talking about the forces they exert on each other?
Since these charges are both positive, they will repel each other. So:
(1) the force on the 5C charge at x = 0 will point in the negative x direction
(2) the force on the 6C charge at x = 40 will point in the positive x direction

Make sense?

5. Aug 4, 2004

### jazzchan

thanks a lot !!