如图1,匀强磁场的方向垂直于纸面,磁感应强度为B,一个质量为m,电量为q,不计重力的带电粒子从O点以速度v垂直射入磁场中,当粒子到达P点时的速度和受力情况如图所示,O、P之间距离为d.将粒子受到的洛仑兹力f和速度v分别沿x轴、y轴方向分解,则有 fx=qBvy,fy=qBvx,得 As shown in Figure 1, the direction of the uniform magnetic field is perpendicular to the paper surface, the magnetic induction intensity is B, a mass is m, and the charge is q. Charged particles excluding gravity are injected into the magnetic field at a velocity v from the point O perpendicularly, when the particle reaches the point P. The velocity and force conditions are as shown in the figure. The distance between O and P is d. The particles are subjected to Lorentz force f and velocity v along the x-axis and y-axis respectively. Then there are fx=qBvy, fy. =qBvx, get