A proton moves at a speed v = 2xx10^(6) m//s in a region of constant magnetic field of magnitude B = 0.05 T. The direction of the proton when it enters this field is theta = 30^(@) to the field. When you look along the direction of the magnetic field, then the path is a circle projected on a plane perpendicular to the magnetic field. How far will the proton move along the direction of B when two projected circles have been completed?

A particle of charge -32 xx 10^(-18) coulomb moving with velocity 20 ms^(-1) along the x-axis enters a region where a magnetic field of induction B is along the y-axis, and an electric field of magnitude 5 xx 10^(4) V/m is along the negative z-axis. If the charged particle continues moving along the x-axis, the magnitude of B is

An electron enters a region that contains a magnetic field directed into the page as shown. The velocity vector of the electron makes an angle of 30^(@) with the +y axis. What is the direction of the magnetic force on the electron when it enters the field ?