Motion of Charged Particle in a Magnetic Field

[SoberSteve2121]

If the velocity is in the i direction (v=vi) and the magnetic field is in the -k direction (B=-kB), prove using Newtons Second Law that the trajectory of this charge must be circular? Please help this is really important.

[Spectre5]

F = qv X B (X = cross product)

F = ma

So,

qv X B = ma

Solve that and think about your solution...don't lose track of your unit vectors....and think about what they mean, what they tell you....