# Coulomb's law

1. May 16, 2004

### wave41

Hi everyone! I really need help with my physics assignment that is due in two days! I have done the problem but I am not even close to being sure if my solution is correct. It is my first year of engineering and I started studying after two year brake in HS and now I am having more trouble with the math, because I forgot so many things....
The question is on Coulomb's law....
A positron is a particle with the same mass as an electron but with a positive charge. Positrons are created in many radioactive particle decays and are present in cosmic rays. A positron and an electron can briefly form an unusual atom known as positronium. Imagine a sutuation where the two particles are in circular orbit about their center of mass. Since the particles have equal mass, the center of mass is midway between them. Let r be the separation of the particles( so the orbits are each of radius r/2)
(a) Show that the orbital period T is related to the separation distance r by T^2= (16pi^3E)(MeMp)/(e^2)(Me+Mp)
This is a consequence of Kepler's third law for electrical orbits. The expression simplifies because the mass of the electron Me is equal to the mass of Mp
T^2= 8pi^3EMe/e^2 r^3
And then there is the second part to it...which I didn't look at yet....I took the two formulas and intigrated them...I am just very unsure about the steps, I am having trouble with the algibra I think....
Thank you....I hope someone can help me...it's percents out of my final grade....
Thanks again

2. May 16, 2004

### Ebolamonk3y

What have you done so far? Show some work..

3. May 17, 2004

### PinkFlamingo

I'm not at home right now, but i think i have this one figured out,. the first part at least. I'll post what I have when I get home tonight. Maybe we can figure the second part out together.

Mandy