# Homework Help: Force between Protons

1. Feb 1, 2009

### jawo3

Hi,

There are 3 Protons (P) that form a triangle.
distance PA-PB -->15mm
distance PB-PC -->20mm
distance PA-PC --> unknown

I have to calculate the last distance and the forces between the protons by using coulomb´s laws.

I tried to calculate the force between AB and BC:
F1=1.02 E -24
F2=5.76 E -25

Now I don´t know what to do next? Can I use the a²+b²=c² for either the Fore or the distance?

Thanks
jawo3

2. Feb 1, 2009

### Delphi51

You've got a triangle with 2 known sides 15 and 20. The third side could be anywhere from 0 to 35 mm and still form a triangle. Do we have any more information to help us decide what the 3rd side is? Something about the forces, perhaps?

3. Feb 1, 2009

### jawo3

The teache or the problem didn´t say it but on the picture that I got it looks like there is a right angle, where Proton B is.

4. Feb 2, 2009

### Delphi51

Well, that makes it easy. Just a geometry question, no physics involved.