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’99高考24题:图中虚线 MN是一垂直纸面的平面与纸面的交线,在平面右侧的半空间存在一磁感强度为 B 的匀强磁场,方向垂直纸面向外,O 是 MN 上的一点,从 O 点可以向磁场区域发射电量为+q、质量为 m、速率为 v 的粒子,粒子射入磁场时的速度可在纸面内各个方向,已知先后射入的两个粒子恰好在磁场中给定的 P 点相遇,P 到 O 的距离为 L.不计重力及粒子间的相互作用.(1)求所考察的粒子在磁场中的轨道半径.(2)求这两个粒子从 O 点射入磁场的时间间隔.
’99 college entrance examination 24 questions: the dotted line MN in the figure is the intersection of a vertical paper plane and the paper surface. In the right half of the plane there is a magnetic field with a magnetic intensity of B, and the vertical paper faces outward. It is a point on the MN. From point O, particles with a power of +q, a mass of m, and a velocity of v can be emitted into the magnetic field. The velocity of the particles when they enter the magnetic field can be in all directions within the paper. The two particles happen to meet at a given P point in the magnetic field, and the distance from P to O is L. The interaction between the particles and gravity is not considered. (1) Find the orbit radius of the particle under investigation in the magnetic field. (2) The time interval between the two particles entering the magnetic field from point O.