Charge moving in elliptical orbit under Coulomb field.

1. Jul 8, 2012

AGNuke

Under the influence of the coulomb field of charge +Q, a charge −q is moving around it in an elliptical
orbit. Find out the correct statement(s).
(A) The angular momentum of the charge −q is constant
(B) The linear momentum of the charge −q is constant
(C) The angular velocity of the charge −q is constant
(D) The linear speed of the charge −q is constant

I am blank at this one. I don't know how to find either one, especially since this is elliptical orbit.

All I know is that since it is elliptical orbit, speed is not constant, so is velocity and thus, linear momentum. Now I am confused between what is constant, angular velocity or angular momentum.

I tried balancing electrostatic force with centrifugal force at any arbitrary point, but so far, I didn't got any satisfactory conclusions from my efforts.

2. Jul 8, 2012

grzz

If there is no torque on the charge then its angular momentum is constant.

3. Jul 8, 2012

Oh! Thanks.