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

A meter stick has two charges placed on it at the 0 mark is a charge of +1 coulomb. On the 100cm mark is a charge of +4 coulombs. Where should a proton be placed on the meter stick so that the net force due to both charges is 0.

2. Relevant equations

Kc = Coulomb const.

Q= charge

a=unknown distance from +1 on proton

b= unknown distance from +4 on proton

X= proton on line

(Kc*Q1*Qn)/r^2= Force 1 on n

3. The attempt at a solution

So far I've attempted to do the following:

+1_________________+4

The proton must fall in some region between the two.

If we take 50cm to be the origin of this system and 100 to be +50cm and -50 to be the negative maximum the system at 0 then the +1 charge acts on it towards the negative X direction. So it goes from this:

0________100cm

to

-50cm_______0_______50cm

-[(Kc*Qproton*Q+1)/a^2]+(Kc*Qproton*Q+4)/b^2 = 0

This however, gives me:

[b^2/a^2]=4/1

b/a=2/1

Which to me says that in order for this equation to be true then the distance to the proton on the +4 charge must be twice that of the distance from +1. However I can't seem to find any reasonable way to put this on the meter stick. The only possibility I can think of that would follow this is that the proton must be 30cm from the +1 charge and 60cm from the +4 charge but this still leaves 10cm that don't exist on the meter stick.

Have been working on this for a few hours now and am beginning to think maybe I'm thinking about this the wrong way. Any help is greatly appreciated.

**Physics Forums | Science Articles, Homework Help, Discussion**

Dismiss Notice

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Homework Help: Columb distance/charge balancing problem

**Physics Forums | Science Articles, Homework Help, Discussion**