A proton starts from rest and is accelerated through a potential difference of 2100 V. The proton then leaves the region of potential difference and enters a region with a uniform magnetic field of 0.10 T. The velocity of the proton and the direction of the magnetic field are perpendicular to one another.
Find (a) the speed of the proton as it enters the region of magnetic field and (b) the radius of the circular path on which the proton moves in the magnetic field.