问题
填空题
活塞式抽气筒的原理如图所示。待抽容器B容积为3L，内部气压强为P0 ，若将它与容积为1L的抽气筒A相连，（设在工作时温度不变），抽气一次后B中压强变为 ；抽气三次后B 中压强变为 .
答案
第一次抽气后，根据波意耳定律可得
,所以
，抽气两次后
，抽气三次后
，所以
.
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活塞式抽气筒的原理如图所示。待抽容器B容积为3L，内部气压强为P0 ，若将它与容积为1L的抽气筒A相连，（设在工作时温度不变），抽气一次后B中压强变为 ；抽气三次后B 中压强变为 .
第一次抽气后，根据波意耳定律可得,所以，抽气两次后，抽气三次后，所以.
| 完形填空。 | |||
| "I don't like my parents. They always tell me I should 1 this, and shouldn't do that. It often makes me unhappy,"said Zhang Li, a middle school student. Do you have the same problem 2 ZhangLi? Why aren't some parents so 3 ? On one hand, parents do a lot for you. They worry about your choice of friends, the food you eat and your study at school. 4 these things are part of your life. Don't blame (责备) them. They want you to 5 up healthily and happily. On the other hand, you 6 introduce your friends to your parents. Let them 7 you are making good friends. 8 them If you stay outside 9 than usual. Don't always argue 10 them. Talk about your ideas with them. You'll understand them when you become a parent in the future. | |||
| ( )1. A. study ( )2. A. about ( )3. A. friendly ( )4. A. Both ( )5. A. stay ( )6. A. shouldn't ( )7. A. know ( )8. A. Surprise ( )9. A. early ( )10. A. with | B. make B. as B. unpleasant B. Whole B. wake B. should B. look B. Remember B. late B. for | C. do C. like C. scared C. All C. keep C. must C. think C. Call C. earlier C. in | D. learn D. to D. busy D. Every D. grow D. needn't D. think D. Talk D. later D. on |
在点m（1，-2，1）的切线一定平行于（）。