Magnetic forces and fields

1. Sep 5, 2007

gamesandmore

An alpha-particle is the nucleus of a helium atom; the orbiting electrons are missing. The alpha-particle contains two protons and two neutrons, and has a mass of 6.64x10^-27 kg. Suppose an alpha-particle is accelerated from rest through a potential difference and then enters a region where its velocity is perpendicular to a 0.0195 T magnetic field. With what angular speed w does the alpha-particle move on its circular path?

B = 0.0195 T
m = 6.64x10^-27 kg

I did this:
v = rw
w = v/r
r = mv/qB
qB/m = v/r
w = qB/m

how ever I am stuck on what is q?

2. Sep 5, 2007

learningphysics

your work looks right to me.

neutrons have 0 charge. protons have $$1.602*10^{-19}C$$ charge. so for your problem q is $$2*1.602*10^{-19}C$$

3. Sep 5, 2007

gamesandmore

thank you! :)