一辆汽车从静止开始匀加速开出，然后保持匀速运动，最后匀减速运动直到停止．从汽车开始运动起计时，表中给出了某些时刻汽车的瞬时速度．根据表中的数据通过分析、计算可以得出( )
| 时刻(s) | 1.0 | 2.0 | 3.0 | 5.0 | 7.0 | 9.5 | 10.5 |
| 速度(m/s) | 3.0 | 6.0 | 9.0 | 12 | 12 | 9.0 | 3.0 |
B．汽车加速运动经历的时间为5 s
C．汽车匀速运动的时间为2 s
D．汽车减速运动的时间为2 s
AD
题目分析：由表中数据可以看出，在9.5s~10.5s内汽车做匀减速运动，其加速度为
，在1.0s～3.0s内做的是匀加速直线运动，其加速度为
，而在5.0～7.0s内做匀速直线运动，所以可知，汽车的最大速度为12m/s，所以可求得汽车的加速时间为
，故A正确、B错误；减速的时间
，所以D正确；由
可知，汽车在9.5s前减速运动了0.5s，所以汽车是在9s时开始减速，即匀速运动的时间为4～9s，即5s，所以选项C错误；
IF and WHEN often had lunch together. Their conversation always 36 on the things they hoped to achieve and they loved to talk about them. ] This particular Saturday when they met for lunch, WHEN 37 IF wasn’t in a great mood（心情）. After they sat at the usual table 38 for them, WHEN asked IF, “You don’t seem your usual 39 self(样子)?” IF replied,“Yesterday I saw a course I wanted to take. If only I 40 the time.” WHEN knew exactly how IF felt and said, “I too saw a 41 and I’ m going to register when I get 42 money.” WHEN then questioned IF, “What about the new job you were going to apply for?” IF answered, “I would have applied, but my 43 broke down. I couldn’t type my resume(简历).” “Don’t worry. I’ve been thinking about looking for another job also, 44 I’ll wait and when the weather gets 45 I will look then. I hate this awful weather.” The man sitting nearby heard them talking about when this and if that. When he couldn’t 46 it anymore, he went to them and said, “I think I know 47 you could solve your problems.” IF smiled and thought that even if he knew the 48 they faced, there was no way he could help! 49 , IF asked the man for advice. The man said, “Your conversation reminds me of an old 50 : IF and WHEN were planted, and nothing 51 .” IF and WHEN both looked surprised and began to feel 52 of living their life for the “ifs” and “whens”. Finally they came to a(n) 53 : next time they met, there would be no “ifs” or “whens”; they would 54 talk about what they had 55 !
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