I seem to be having trouble starting this one:

An ion enters a mass spectrometer which has a 0.18 Tesla field perpendicular to an electric field of 1.6 kV/m and selects a velocity. The same magnetic field is then used to deflect the singly charged ion into a circular parth of radius 12.5cm.

a) What velocity was selected?
b) What was the ion mass?

Using r = mv/qB I can calculate that mv = 3.6 x 10^-21....but I'm not sure where to go from there :)

Question

I seem to be having trouble starting this one:

An ion enters a mass spectrometer which has a 0.18 Tesla field perpendicular to an electric field of 1.6 kV/m and selects a velocity.  The same magnetic field is then used to deflect the singly charged ion into a circular parth of radius 12.5cm.

a) What velocity was selected?
b) What was the ion mass?

Using r = mv/qB I can calculate that mv = 3.6 x 10^-21....but I'm not sure where to go from there :)