两颗靠得很近在天体称为双星，它们都绕两者连线上某点做匀速圆周运动，因而不至于由于万有引力而吸引到一起，则以下说法中正确的是（ ）
A．它们做圆周运动的角速度之比与其质量成反比
B．它们做圆周运动的线速度大小之比与其质量成反比
C．它们做圆周运动的半径与其质量成正比
D．它们做圆周运动的半径与其质量成反比
A、因为双星各自做匀速圆周运动的周期相同，根据角速度与周期的关系可知：ω=
，双星的角速度之比为1：1，故A错误；2π T
CD、双星做匀速圆周运动的向心力由万有引力提供，G
=m1ω2R1=m2ω2R2，所以m1m2 (R1+R2)2
=R1 R2
，故C错误、D正确．m2 m1
B、根据线速度与角速度的关系v=ωR，所以
=v1 v2
=R1 R2
，故B正确．m2 m1
故选：BD．
| Jerry在欣赏一篇美文，可是中间缺了一些词，请你动动脑筋从所给的四个选项中选出恰当的词，使它成为一篇完整的短文。 | ||||
| A rich father wanted to show his son how poor people can be. One day, he took his young son 1 a trip to the country. They 2 a day and night in the farm of a very 3 family. When they got back from their trip the father asked his son, "how was the 4 ?" "Very good, Dad!" "Did you see how poor people can be?" the father asked. "Yeah!" "And what did you 5 ?" The son answered, "I saw that we have a dog at home, but they have four. We have a pool that reaches to the middle of the garden. They have a small river that has no 6 . We have expensive lamps in the garden, but they have the 7 . Our…" When the little boy was finishing, his father was 8 . His son added, "Thanks, dad, for showing me 9 poor we are!" Isn't it true that it all depends on the way you look at things? If you have love, friends, family, health, good humor and a positive attitude (积极的态度) toward life, you've got 10 ! | ||||
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