# Finding velocity of particles in a uniform magnetic field

1. The problem statement, all variables and given/known data
Given are a uniform electric field, E = 30,000 V/m inside a capacitor (see picture), and a uniform magnetic filed, B = 10 T, perpendicular to the plane of the page, present in all of the area.

Identical charged particles are moving in a trajectory marked by the dashed line, under the influence of the two fields: The trajectory inside the capacitor is a straight line, and the trajectory outside the capacitor is circular, with radius r = 1 cm. What is the velocity v of the charged particles?

2. Relevant equations

Possibly r = mv / qB , but I don’t know the mass of the particle.
Maybe E = F/q

3. The attempt at a solution

I know that the magnetic field is into the page based on the RHR. The particle is in circular motion because of the velocity and magnetic force vectors. The answer is v = 3000 m/s but I have no idea how it was derived.
1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution

http://ift.tt/1kpoETn