[SOLVED] A question about Magnetic Fields and A Charge A charged particle enters in 90 degrees to the magnetic field i.e. the force on the charge is F = qvB as sin (angle) = 1. The question is which are the effects on the kinetic energy and momentum of the particle? Alternatives: A. KE => Changed Momentum => Changed B. KE => Unchanged Momentum => Changed The solution is B but I do not why? Please, help me.