# Homework Help: Physics Electric Field Problem

1. Feb 16, 2013

### asheik234

1. The problem statement, all variables and given/known data
A particle with a mass m and a charge Q is accelerated through a potential difference V, causing its kinetic energy to increase by an amount K. Another particle of mass m/5 and charge 2Q is accelerated through the same potential. How much kinetic energy does this second particle gain?

2. Relevant equations
Vq = U

(1/2)mv^2 = U;

3. The attempt at a solution
I can't find an equation that relates mass, charge and kinetic energy. Any help would be appreciated.

2. Feb 17, 2013

### Staff: Mentor

It seems that you don't need to involve mass.

Remember, 1 volt = 1 joule of energy per coulomb

3. Feb 17, 2013

### asheik234

If Q*C = K;
then 2Q*C = 2K'

So the increase in kinetic energy is K, correct me if I'm wrong.

4. Feb 17, 2013

### haruspex

I think you mean 2Q*C = K'

5. Feb 17, 2013

### asheik234

Then the kinetic energy doesn't change?

6. Feb 17, 2013

### haruspex

K' stands for the KE of the 2Q charge, right? (Just noticed the OP uses V, not C, so switching back to that here...)
If Q*V = K and 2Q*V = K' then what is the relationship between K and K'?

7. Feb 17, 2013

### asheik234

So K' = 2K, right, because Q is proportional to KE.

8. Feb 17, 2013

### Staff: Mentor

Right, because KE is proportional to Q here.

Remember, 1 volt = 1 joule per coulomb