A non-relativistic charged particle files through the electric field of a cyclindrical capacitor and gets into a unifrom transverse magnetic field with induction `B`(fig). In the capacitor the particle moves along the are of a circle, in the magnetic field, along a semi-circle of radius `r`. The potential differnce applied to the capacitor is equal to `V`, the radii of the electrodes are equal to `a` and `b`, with `a lt b`. Find the velocity of the particle and its specific charge `q//m`.