2022英语周报高三OJS答案

.C【解析】带电粒子在磁场中运动,不计重力,则只受洛伦兹力做圆周运动有BR,所以=粒子沿θ=60°方向射入时,恰好垂直PQ射出,则粒子在磁场中转过30°如图甲所示,所以有Rsin30°=a,解得R=2a,粒子运动的时≈307=R_m360°6v6qBA正确。如图乙所示=0时,粒子离开磁场的位置在PQ上O的水平线上方√3a处;当θ增大时,粒子离开磁场的位置在PQ上的位置下移,直到粒子运动轨迹与PQ相切;θ继续增大,则粒子不能从PQ边界射出;粒子运动轨迹与PQ相切时,由半径R=2a可知,粒子转过的角度为120°出射点在MN上O的水平线下方2√3a处,此时01=120°,粒子在磁场中运动的时间最长,B正确。当120°<0<180°时,粒子从MN边界射出,且0越大,对应的中心角越小运动的时间越小,所以MN边界上有粒子射出的长度为2√3a,粒子在磁场中运动不存在最短时间,C错误,D正确。故选C。PM、元OXXNBQ、NQ甲乙

第二节One possible versionDear Mr. TomIm writing to invite you to be present at the recitationcontest organized by the reading club at 3: 00 next Wednes-day afternoon in the lecture hall. If available then. couldyou do us a favor? And we would appreciate having you as ajudge. By the way, it would be very nice if you can recommend some classic English literary works suitable for usstudentsanks for considering our requestIm looking forward to your reply at your earliest con-venience lYours sincerelyLi Hua

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