放在光滑水平面上的A、B两小车中间夹了一压缩轻质弹簧（并末拴接在一起），用两手分别控制小车处于静止状态，已知A的质量大于B的质量，下面说法中正确的是（ ）
A．先放开右手，后放开左手，此后两车的总动量向右
B．先放开左手，后放开右手，此后两车的总动量向右
C．两手同时放开之后的过程中，A车的动量与B车的动量不同
D．两手同时放开之后的过程中，A车的速度大于B车的速度
A、若先放开右边的B车，后放开左边的A车，放开A车时，B车已经有向右的速度，系统的初动量不为零，两车的总动量向右．故A正确
B、先放开左手，A车已经有向左的速度，后放开右手，此后两车的总动量向左，故B错误
C、两手同时放开之后的过程中，系统动量守恒，但是A车的动量与B车的动量方向相反，所以A车的动量与B车的动量不同，故C正确
D、两手同时放开之后的过程中，系统动量守恒，已知A的质量大于B的质量，所以A车的速度小于B车的速度，故D错误
故选AC．
| 完形填空。 | ||||
| I like 1 best. Last week, I saw a movie called I Robot. It tells us a story about the future with robots (机器人). It is the year of 2035 and people can see robots everywhere. Robots can help people do a lot of things, like looking 2 the old people or babies, washing, cooking, cleaning or taking dogs for a 3 . Robot does everything people ask them to do. But a policeman 4 Spooner. He doesn't like robots. Because he doesn't think that people can live well 5 robots. One day a scientist kills himself (自杀). He leaves (留下) a robot. Some time later Spooner finds 6 wrong with the robots in the world. A 7 robots have their own thoughts (思想) and want to control (控制) the people. If the robots succeed. it will be very 8 for people. Susan is another scientist working on robots. Finally, Susan and Spooner decide 9 work together to fight against these robots. At last, they succeed (成功). People control the robots again. I think the movie is very interesting. 10 you have interest in it, why not go and see it? | ||||
|
