Consider the mass spectrometer shown schematically in Figure P19.30. The electric field between the plates of the velocity selector is 850 V/m, and the magnetic fields in both the velocity selector and the deflection chamber have magnitudes of 0.910 T. Calculate the radius of the path in the system for a singly charged ion with mass m = 2.18 x 10-26 kg. (Hint: The figure is of a mass spectrometer. Charged particles are first sent through a velocity selector. They then enter a region where a magnetic field B_0 (directed inward) causes positive ions to move in a semicircular path and strike a photographic film at P)
r = mv/qB
The Attempt at a Solution
I know that I am suppose to use the above formula but I am having a problem finding v. I am not sure what formula I am suppose to use to find the velocity with the given number.
Any help would be appreciated