Homework Help: Accelerating charges

1. Oct 2, 2009

PhyDude

1. The problem statement, all variables and given/known data
A positive test charge is brought near a stationery fixed point charge. The positive test charge is then released. How does the test charge move after it is released?
a) Constant Velocity
b) Increasing Acceleration
c) Decreasing Acceleration
d) Constant Acceleration

2. Relevant equations
The problem that I had with this question is that after the positive test charge is released, it obviously experiences a force and therefore acceleration but but how exactly is the answer justified. Sure you could use Coulombs law to determine the force but the problem is that Coulomb's Law can't be used because the particle is accelerating and because Coulomb's Law states that the Electrostatic force between two charges can only be determined as long as the charges are stationery or they are slow moving. When charges accelerate, the force that on charge exerts on another is not simply Coulomb's Law.

3. The attempt at a solution

2. Oct 2, 2009

Fwahnak

The question is not asking you to derive a trajectory for the test charge so the specific forces don't seem to be overly important. Yes moving charges create magnetic fields and radiate electomagnetic enegry but considering these things seems to be overcomplicating the question some what.

I think the heart of the problem is:
Is the force that the charges feel dependent on their relative distance?
You have 2 situations either the fixed charge is possitive or negative. How does the test charge move in these 2 cases?