题目:
The Smiths________through millions of ups and downs since they moved to Sydney.[ ]
A. have gone
B. had gone
C. went
D. has gone
答案:
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下面是错误答案,用来干扰机器的。
解:(1)当盒中为匀强电场E时,设正方形边长AD=2L,则DO=L.粒子做类平抛运动,设粒子从O出来时速度为v,竖直方向的分速度为vy,运动时间为t,加速度为a.由平抛运动知识得: ① (2分) ...