# Homework Help: Voltage contributing to acceleration of a particle before entering mass spectrometer?

1. Mar 31, 2009

1. The problem statement, all variables and given/known data

A doubly charged helium atom whose mass is 6.6 \times 10^{ - 27} {\rm{kg}} is accelerated by a voltage of 2800 V.
What will be its radius of curvature if it moves in a plane perpendicular to a uniform 0.370 -T field?
What is its period of revolution?

2. Relevant equations
F=qvB
centripetal acceleration = (v^2)/r
P= 1/f

3. The attempt at a solution
I know that F=ma, and a= (v^2)/r, and so r will = mv/qB.

My principle question is how can I find out the particle's initial velocity in the magnetic field based on the voltage that accelerates the atom? Also, what is the charge of a "doubly charged" He atom and how do you know? I understand the magnetism principles behind it but am having difficulty figuring out the speed at which the particle enters the mass spectrometer. Thank you... I appreciate the help!

2. Mar 31, 2009

### alphysicist

Re: Voltage contributing to acceleration of a particle before entering mass spectrome