Distance of ions from photographic plate

[sarahaha288]

Homework Statement

How far would the spot on the photographic plate be from the entry point for each ion, assuming that each ion completes half an orbit?
I am given three ions, N+subscript2, O+subscript2, NO+
They have atomic masses of N=14.0031amu and O=15.9949amu.
I am given the magnetic field strength=8.5MN/C
velocity=30.0km/s
The magnetic field is uniform and perpendicular to the velocity.

Homework Equations

I tried to use R=mvc/ qB

q is the charge, m=mass, v=speed, c=speed of light, B= magnetic field strength

The Attempt at a Solution

I tried simply substituting these in and using the standard 1.60*10^-19C for the charge. For the mass i just took the atomic mass, multiplied it by the subscript of two for the first two and then converted it to kg.
I got it wrong.. and i can't tell why.
If i could just figure out what i did I'm pretty sure it's the mass or the charge that is incorrect but i have not had chemistry in quite awhile and can't figure it out...

Thanks for all your help in advance!

 

[ideasrule]

Think about it more. Do the ions really hit the plate 1 radius away from their starting position?

 

[sarahaha288]

No. I think it's 2R now. Thank you... I'm not sure how i overlooked that.