题干

甲、乙两人站在光滑的水平冰面上,他们的质量都是M,甲手持一个质量为m的球,现甲把球以对地为v的速度传给乙,乙接球后又以对地为2v的速度把球传回甲,甲接到球后,甲、乙两人的速度大小之比为(   )

A:2MMm

B:M+mM

C:2(M+m)3M

D:MM+m

上一题 下一题 0.0难度 选择题 更新时间:2015-06-04 08:31:01

答案(点此获取答案解析)

D

同类题3

阅读理解

    According to a recent study out of the University of Pennsylvania's Wharton School, men with shaved heads are considered to be more manly, powerful, and successful than those with longer hair or thinning(稀少的) hair. Besides, in some cases, they are considered to have greater leadership potential (潜力). That may explain why the power-buzz look has become popular among business leaders in recent years.

    Albert Mannes, Wharton management lecturer, said he was encouraged to do the research after noticing that he was treated with more respect when he shaved off his thinning hair.

    Mannes did three experiments to test people's impression of men with shaved heads. In one of the experiments, he showed 344 subject photos of the same men in two versions: one showing the men with hair and the other showing them with their hair digitally removed, so their heads appear shaved. In all three tests, the subject report found the men with shaved heads are more dominant(占优势的) than their hairy counterparts(对应的人).

    The study found that men with thinning hair were viewed as the least attractive and powerful. For those men, the solution could be as cheap and simple as a shave.

    New York image consultant Julie Rath advised her clients to get closely cropped when they start thinning up top. “There is something really strong, powerful and confident about laying it all bare(光秃的),” she said, describing the thinning look as kind of raunchy(不修边幅的).

    Not everyone needs a bare head. Rick Devine, 55, the CEO of Devine Capital Partners, advised executive candidates attracted by their clippers to keep their hair closely cropped, rather than completely shaved. “It is way too much image risk,” he said, “The best thing you can do in a business meeting is to make your look not an issue.”

根据短文内容,选择最佳答案,并将选定答案的字母标号填在题前括号内。