An alpha particle (the nucleus of a helium-4 atom) consists of two protons and two neutrons. A horizontal beam of alpha particles is injected with a speed of 1.3 X 105 m/s into a region with a vertical magnetic field of magnitude 0.155 T. (a) how long does it take for an alpha particle to move halfway through a complete circle ? (b) if the speed of the alpha particle is doubled, does the time found in (a) increase, decrease or stay the same ? Explain.