# Homework Help: Electrostatic Forces on Particles

1. May 27, 2008

### DMac

[SOLVED] Electrostatic Forces on Particles

"An Astatine 219 nucleus and an alpha particle at a spacing of 1.5 x 10^-15 m are formed during alpha decay. If the initial velocity of the two particles is zero, calculate the ratio of their velocities."

I was thinking of making a ratio of their kinetic energy, but I'm not sure if that's simplifying the problem too much.

If I make a ratio, I get:
.5 x m1 x v1^2 : .5 x m2 x v2^2
...

v1
--- = sqrt [m2 / m1]
v2

Is this right?

2. May 27, 2008

### gendou2

Seems right to me. Conservation of kinetic energy is a handy trick!

3. May 27, 2008

### DMac

I'm just not sure if it can be done any other way....because I certainly cannot use force (since force varies with the distance, just like the gravitational potential well). So all I could think of was energy.

However, I'm particularly unsure because my manipulation basically equates the two kinetic energies; that is, the energy of the alpha particle is the same as that of the astatine particle.

4. May 28, 2008

### gendou2

Yes, the energies are the same, but the velocities are different.
This is due to the different masses.