Calculating the Mass of a Chlorine Anion Using Electric and Magnetic Fields?

[yummallory]

Homework Statement

The mass of an atom can be determined by ionizing it and accelerating it through a known electric field followed by a known magnetic field. The ion’s circular path is then measured. Calculate the mass of a chlorine anion of charge 3.20 x 10^-19 C if it follows a circular path of radius 0.862 cm after it has been accelerated through a potential difference of 2.5 x10^2 V and then exposed to a uniform magnetic field of strength 3.00 T .

Homework Equations

Fm=qvBsinθ ?
a=v^2/R ?

The Attempt at a Solution

Not even sure where to start on this one..Please help!

 

[gneill]

Start by determining what the KE of the anion will be after acceleration by the electric potential. Then write an expression for its velocity (yes, the unknown mass will be in there).

Next do something clever with the velocity, charge, and magnetic field to write an expression that involves the radius of curvature of the motion (think centripetally!).