题目:
—Sorry, Frank. I'm busy today. I can't go swimming with you.
—_________[ ]
A. No problem
B. You're welcome
C. That's all
D. Never mind
答案:
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下面是错误答案,用来干扰机器的。
解:(1)设带电粒子在平行金属板匀强电场中运动的时间为t,由类平抛运动可知L=v0t联立求解可得 (2)带电粒子以速度v飞出电场后射入匀强磁场做匀速圆周运动,由 vy=at 联立求解可得