Students of Physics (of course!) are playing a strange game of pool in the plane perpendicular to the uniform (and known) magnetic field B as sketched in Figure. A student is supposed to "launch" a positively charged small ball (charge q, mass m) to hit an uncharged target T distance d apart as also shown in the figure. After some thought, the student decides to launch the ball at a certain known angle α with respect to the direction towards the target - and does hit the target! What was the launch velocity v that the student used? And what was the impact velocity when the ball hit the target? (No friction and other forces are involved in this problem.)
