题干

宇宙中,两颗靠得比较近的恒星,只受到彼此之间的万有引力作用互相绕转,称之为双星系统,设某双星系统绕其连线上的O点做匀速圆周运动,如图所示.若AO<OB,则(   )

A:星球A的向心力一定大于B的向心力

B:星球A的线速度一定大于B的线速度

C:星球A的质量一定大于B的质量

D:双星的总质量一定,双星之间的距离越大,其转动周期越大

上一题 下一题 0.0难度 选择题 更新时间:2011-11-28 10:09:56

答案(点此获取答案解析)

C,D

同类题2

阅读理解

    It's generally believed that people act the way they do because of their personalities and attitudes. They recycle their garbage because they care about the environment. They pay $5 for a caramel brulee latte because they like expensive coffee drinks.

    It's undeniable that behavior comes from our inner dispositions(性情),but in many instances we also draw inferences about who we are,as suggested by the social psychologist Daryl Bern,by observing our own behavior.We can be strangers to ourselves.If we knew our own minds,why would we need to guess what our preferences are from our behavior?If our minds were an open book,we would know exactly how much we care about the environment or like lattes.Actually,we often need to look to our behavior to figure out who we are.

    Moreover,we don't just use our behavior to learn about our particular types of character—we infer characters that weren't there before.Our behavior is often shaped by little pressures around us,which we fail to recognize.Maybe we recycle because our wives and neighbors would disapprove if we didn't.Maybe we buy lattes in order to impress the people around us.We should not mistakenly believe that we always behave as a result of some inner disposition.

    Whatever pressures there can be or inferences one can make,people become what they do,though it may not be in compliance(符合)with their true desires.Therefore,we should all bear in mind Kurt Vonnegut's advice:"We are what we pretend to be,so we must be careful about what we pretend to be."