有一个老太太提着一个篮子西瓜去卖，第一个人买走了她的西瓜的一半又半个；第二个人买走了剩下的一半又半个；第三人买走了前两个人剩下的一半又半个，正好卖完全部西瓜，问老太太一共卖了多少个西瓜．

完成句子。
1. It's not just because they ____（不能理解它是什么意思）.
2. F 2 F ____ （表示面对面）.
3. Homophone often use letters and numbers that ____（听起来像单词或单词的一部分）.
4. I don't think twelve-year-olds should be allowed to ____ （穿耳洞）.
5. I think teenagers should be allowed to____（与朋友们外出）.
6. If we can't wear our own clothes, we should be allowed to____ （设计自己的校服）.
7. I get nervous before big parties and then I ____（出皮疹）.
8. It isn't good to borrow your friends' books ____ （未经允许）.
 9. My life ____（有了很大的改变）in the last few years.

如图所示，长0.40m的细绳，一端拴一质量为0.2kg的小球，在光滑水平面上绕绳的另一端做匀速圆周运动，若运动的角速度为5.0rad/s，绳对小球需施多大拉力____N。