水龙头开口竖直向下，直径为1cm，安装在离接水盆75cm高处，现打开水龙头，水沿竖直方向流下，仔细观察将会发现连续的水流柱的直径在流下的过程中是不断减小的，现测得水在水龙头出口处的速度大小为1m/s，求水流柱落到接水盆中时的直径。（g取10m/s2）
解：水流下落达到稳定时，在任一段时间内，流过任一水柱截面的水的体积是一定的，即各处流量相等。由于水在下落过程中的速度不断变大，所以横截面积不断变小如图所示
自由落体：vt2-v02=2gh
流量相等：
代入数值可得：r=0.5cm
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| Anorexia nervosa is an eating disorder that I struggled with for most of my middle school years and a part of my high school years. At Riverview, 1 was usually a nightmare (噩梦) for me. As I 2 the dining hall, all the eyes would be fixed upon my bony figure. I would take my place at a table full of friends and 3 to enjoy a "normal" lunch. The 4 was that I would not always eat lunch, and that greatly 5 my friends. They would watch to make sure that I was eating properly, almost 6 food into my mouth. And then, I transferred to Madison High School. I decided not to tell anyone at that school about my eating disorder since I had almost 7 by that time. Strangely, I stopped fearing lunch when I started at Madison. No one knew that I had an eating disorder, 8 they did not care what I ate. This 9 a huge amount of stress from my life. It was still hard for me to eat in front of others, which is 10 for an anorexic, but I was able to put some of my 11 aside. I was thankful for the students at Riverview, but they knew me only as an anorexic. My friends cared about my health, but they 12 to care about me as a person. Truthfully, all I wanted was for them to 13 me and not to fix on my eating disorder. The students at Madison took the time to know who I 14 was. They had no idea that I had been an anorexic, so that a particular label (标签) did not 15 their opinions of me. I was finally 16 for my talents and achievements, not my failures. I was honored as a good student. I was no longer afraid to show my true 17 . My days as an anorexic taught me many lessons that I would never 18 . They taught me about life and how to be a better friend. I learned about the joy of 19 tasks such as eating lunch. I appreciated the people who helped me to see that there is more 20 life than having an eating disorder. | ||||
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