2022高二英语周报39期答案

25.(20分【答案1)1=y2kBR(2)(-R【解析】(1)因为小球A静止在Q点,所以与A球质量和电荷量相等的B球将向右做匀速直线运动,然后与A球相碰,设两球的质量为m,B球的初速度大小为vo,A、B碰撞后的共同速度为v1根据动量守恒有m=解得v1常由王体号在碰撞前处于静止状态,则vE=m解得q=(1分)粒子进入磁场后做匀速圆周运动,设小球在磁场中做圆周运动的半径为r,根据粒子运动的轨迹,依据几何关系=R(分)根据牛顿第二定律有qB=m(2分)解得w=y2gBRE(1分)(2)由题意可知,粒子从P点出射的速度大小更多试题,关注新浪微博(1分)粒子在进磁场前做类平抛运动,进磁场时的速度的反向延长线交于水平位移的中点,则粒子进磁场时速度与x轴正向的夹角为45°,则粒子进磁场时的速度大小v=√2w’(1分)粒子在磁场中做匀速圆周运动,则qv2B=mv2解得n=yR(1分)由几何关系可知,粒子在磁场中做圆周运动的圆心位置为(,0)(1分)新浪微博滴考有界场边界满足x2+y2=R2(1分)粒子在磁场中做圆周运动的轨y2=n(1分)解得x=3因此粒子出磁场时的位置坐标为(3R,=R(1

第三节One possible version:Children are widely exposed to alcohol and thus have amisunderstanding of it very early. However, without realizing the problem, parents don' t pay enough attention to it.Unluckily, according to research, teenage drinking is veryserious in North Dakota, which might result in variousproblems. Since children and teenagers tend to ask theirparents for guidance in making decisions, it s parentsuty to communicate with children about alcohol in time.

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