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.
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| Once when I was a teenager, my father and I were standing in line to buy tickets for the circus (马戏团). This is about the family standing ahead of us. The family had eight children. Their clothes were not expensive but 1 . The children were well behaved. They stood in line, two by two behind their parents, holding hands. They were excitedly talking about the clowns (小丑), elephants and other acts they would see that night. You could 2 that they had never been to the circus before. The ticket lady asked the father how many tickets he wanted. He 3 replied, "I want eight children's tickets and two adult tickets please, so I can take my 4 to the circus." The ticket lady quoted (报) the price. The man's wife let go of his hand. The man's lip started to quiver (颤抖).He leaned (靠) toward 5 and asked again, "How much did you say?" The ticket lady quoted the price again. The man didn't have 6 money. How was he supposed to tum and tell his eight kids that he couldn't take them to the circus? My dad put his hand into his pocket, pulled out a $20 bill and 7 it on the ground. (And we weren't rich!) Then he 8 down, picked up the bill, tapped the man on the shoulder and said, ''Excuse me, sir, this 9 out of your pocket." The man knew 10 was going on. He looked into my dad's eyes, held my dad's hand in his, and took the $20 bill. With a tear in his eye, he replied,"Thank you, thank you, sir. This really 11 a lot to me and my family." My father and I went back to our car and drove home. We didn't get to see the circus that night, but we didn't 12 . | ||||
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