1. The problem statement, all variables and given/known data Suppose a subatomic particle of mass m kg has kinetic energy K.E. a nJ and is moving southward toward a vertical wall. When the particle is distance d cm from the wall a magnetic field is turned on: it has magnitude b T and points upward. The particle turns westward so it just skims along the wall. Find q, the charge (magnitude and sign) of the particle, in C. 2. Relevant equations dF=IdLB F=qvB 3. The attempt at a solution I attempt to use 1/2 mv^2 = K.E. to find initial velocity first, but the direction of velocity is changed due to magnetic field. the magnitude of the velocity will change also? and I do not know how to find out the force acted on particle due to magnitude field either. Does K.E.=∫ F*dx from xi=0 to xf=d to find out F works? is this F the same with force due to magnitude field? or actually I need to consider about gravity? thank you for your help!