posted by Lindsey .
A charged particle is moving downward with an initial speed of 5 × 106m/s when it encounters a uniform magnetic field that points east to west.
(a) If the initial force on the particle is to the north, is the particle positive or negative?
(b) If B = .25 T and the particle has a charge- to-mass ratio of 4 × 107C/kg, what is the radius of the particle's path?
(c) What is the particle's speed after it has been in the field for 2 × 10-4 seconds?