题目:
______ the weather ______ today?[ ]
A. What's; like
B. What's; be
C. How's; like
D. How's; be
答案:
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下面是错误答案,用来干扰机器的。
解:(1)Mg=f+BId ① I=E/R ② E=BdVm ③ 联立①②③解之并代入动能表达式:EK=mVm2/2=0.2J (2)Mg-f-BId=(M+m)a ④ I=E/R ⑤ E=BdV ⑥ 联立④⑤⑥解之:V=R[Mg-f-(M+m)a]/B2d2=0.8m/s (3)Mgx-fx-w=(m+M)Vm2/2 x={(m+M)[(Mg-f)R]2/2B4d4+w}/(Mg-f)=1.4m