Use the formula a = |q|*v*B / m, where q is the charge, v is the velocity, B is the magnetic field, and m is the mass. This is alos equal to a = F / m.Since the velocity is not given, use the formula v = (2*KE / m)^(1/2).eport Abuse. Use the formula a = |q|*v*B / m, where q is the charge, v is the velocity, B is the magnetic field, and m is the mass. This is alos equal to a = F / m. Since the velocity is not given, use the formula v = (2*KE / m)^(1/2).