In the xy-plane, the region y > 0 has a uniform magnetic field B1k and the region y < 0 has another uniform magnetic field B2k. A positively charged particle is projected from the origin along the positive y-axis with speed v0 = πms-1 at t = 0, as shown in the figure. Neglect gravity in this problem. Let t = T be the time when the particle crosses the x-axis from below for the first time. If B2 = 4B1, the average speed of the particle, in ms–1, along the x-axis in the time interval T is __________.
