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[例]在空间有水平方向、彼此垂直正交的匀强电场和匀强磁场,场强分别为E和B,有一足够长的直杆竖直放置电、磁场中,有一带电小球穿过直杆上,小球可在直杆上上下滑动。若小球质量为m,带电量为q,小球与杆的动摩擦因素为u,当小球从静止开始释放后,则在什么情况下小球有最大速度?最大速度是多少?什么情况下有最大加速度?最大加速度是多少?[分析]以小球为研究对象,小球刚开始释放时速度V=0不受
[Example] A uniform electric field and a uniform magnetic field perpendicular to each other in a horizontal direction and perpendicular to each other, the field strengths being E and B, respectively, and a straight rod of sufficient length to be vertically elec- trical. In the magnetic field, a charged pellet passes Straight rod, the ball can slide up and down in the straight rod. If the mass of the ball is m and the charge is q, the dynamic friction factor between the ball and the rod is u. When the ball is released from rest, under what conditions does the ball have the maximum velocity? What is the maximum velocity? There is the maximum acceleration? What is the maximum acceleration? [Analysis] to the ball as the object of study, the ball started to release speed V = 0 from