一、试题及分析如图1,在直角坐标系xOy内,有一质量为m、电荷量为+q的带电粒子(重力不计)从原点O沿y轴正方向以初速度v0出发,现要求该粒子在运动的空间范围内加上电场或磁场(每个象限最多一种场)后,该粒子最后能通过点P(a,-b)。试设计一种能实现这一目的的简单、常规的方案,要求:(1)说明粒子由O到P的运动性质并在图中绘出粒子的运动轨迹; First, the test questions and analysis Figure 1, in the Cartesian coordinate system xOy, there is a mass m, the charge amount of charged particles q (excluding gravity) from the origin O positive direction along the y-axis at an initial velocity v0, is required Particles can eventually pass through points P (a, -b) after the particles have applied an electric or magnetic field (up to one field per quadrant) within the spatial extent of the motion. Trying to design a simple, routine solution to this end requires: (1) to explain the particle's motion from O to P and to plot the trajectories of the particles;