为确定爱因斯坦质能联系方程ΔE=Δmc2的正确性，设计了如下实验：用动能为E1="0.9 " MeV的质子去轰击静止的锂核
Ｌi，生成两个α粒子，测得这两个α粒子的动能之和为E="19.9" MeV.
(1)写出该核反应方程；
(2)计算核反应过程中释放出的能量ΔE；
(3)通过计算说明ΔE=Δmc2的正确性.(计算中质子、α粒子和锂核Ｌi的质量分别取：mp="1.007" 3 u，mα="4.001" 5 u，mＬi="7.016" 0 u)
（1）
H+
Li→2
He
(2)18.9 MeV (3)略
(1)H+Ｌi→2He.
(2)Δm="(1.007" 3+7.016 0-2×4.001 5)u="0.020" 3u
ΔE="0.020" 3×931.5 MeV="18.9" MeV.
(3)反应前后系统总动能的增加为
E-E1="19.9" MeV-0.9 MeV="19.0" MeV
这与核反应释放的核能在误差允许范围内近似相等，说明ΔE=Δmc2是正确的.
完形填空 I came to study in the US last fall. My life had been quite 1 since I arrived at Andover. Although I had quite a few extracurricular (课外的) activities, I hadn’t taken any official leadership position. This 2 changed when I received an e-mail from Ms Griffith, my cluster dean (主 任), 3 that a few female DC Rep was needed. DC Rep 4 Discipline Committee Representative. 5 boarding school students break serious rules, like using 6 , getting drunk or cheating in the studies. The punishments given to such students are 7 by a DC Rep, a house counselor, two student representatives, the cluster dean. I was really interested in becoming a DC Rep for my cluster, Pine Knoll, 8 so were five other students. We had to hold 9 and Ms Griffith asked us to write 10 to be sent to everyone in Pine Knoll. I thought hard about what to write. I didn’t want to make any 11 because they are difficult to keep. I didn’t want to say I was experienced, because I was not. So I started my speech by explaining 12 I wanted to become a DC Rep. “ I want to serve Pine Knoll and also learn how American boarding schools carry out disciplines,” I wrote 13 . I made three 14 that said “ Vote For Teresa” and put them on every exit (出口处) of my dorm so that people would 15 my name when they went to vote. Although I tried hard, I didn’t win the election, I was 16 . But my positive nature didn’t allow me to 17 for very long. I actually 18 when my friends tried to comfort（安慰） me. “Teresa, I’m sorry that you didn’t win the election,” they would say. “ No, don’t be sorry for me. I am very happy to have taken part in the election.” I said. It is true: the 19 is much more important than the result. I am surprised and happy to discover my hidden 20 .
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