# Homework Help: Couple of questions! Please help! Point particle orbiting two charges

1. Oct 15, 2007

### mrk442

1. The problem statement, all variables and given/known data
Two Point particles with charge +Q lie on the z axis at z=+d/2 and z= -d/2 a point particle with charge -Q and Mass=m is orbiting in the X-Y plane in a circular radius=r the path of the orbit is thus z=0, x^2+y^2=r^2

A. find the total coulomb force on the positive particles in the Z direction the Z component

B. Set Fz from equation a. to equal 0 and solve for r in terms of d

C.find the radial force in the x-y plane acting on the negative particle and set it equal to the centripital force required to keep the particle in the circular orbit.

D.solve c. for mv^2 in terms of d,Q,r,etc

E. Find the potential energy of the three electrostatic interactions in the system.

F. Express kinetic energy using the reults in D, find the total energy of the system.
in H2+ molocular ion, protons with Q+ =1.6x10^-19 coulombs are seperated by a distance d=100pm = 106x10^-12 while a lone electron with m=9.1x10^-31kg,-Q=-1.6x10^-19 C orbits the center plane.

G. Use b. to find the radius of the clasical orbit of the electron.

H. Use f. to find the total energy of the ion in Joules. it should be negative if the ion will stay together.

I. express the result h. in unit elexctron volts.

2. Relevant equations
Coulombs
PE
Kinetic energy

3. The attempt at a solution
I missed a few days of class and we where given this question 1 of 4 as prep for our test I am really at a loss for where to begin here? I assume for a. i can ignore the -Q charge since it does not lay on the z access or afect the z component but i am not sure. i am actually not really sure at all what to do with some of the rest. i am going through the book as i type this but i am a little stuck since i missed two weeks of class when i hurt my back any help to get me going would be apreciated i have a couple of other questions i might post later if i dont work them out.

thanks again!!!

2. Oct 15, 2007

### Astronuc

Staff Emeritus
3. Oct 15, 2007

### mrk442

Thanks i will start with that :) and post my results or as i run into issue any help is always welcome :)

Thanks again
matt