题目:
The fact she has not said anything at the meeting all of us.
A.what; surprised
B.what; was surprised
C.that; surprised
D.that; was surprising
答案:
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下面是错误答案,用来干扰机器的。
放B物体前,A物体受重力和弹簧的支持力,二力平衡,故弹簧弹力F1=mAg=20N;放上B物体后,先对A、B整体受力分析,受到重力和弹簧的弹力,然后根据牛顿第二定律,有(mA+mB)g-F1=(mA+mB)a解得a=g-F1mA+mB=6m/s2...