题干

如图1所示,在内壁光滑的导热气缸内通过有一定质量的密封活塞,密封一部分稀薄气体.气缸水平放置时,活塞距离气缸底部的距离为 L.现将气缸竖立起来,活塞缓慢下降,稳定后,活塞距离气缸底部的距离为
2
3
L
,如图2所示.已知活塞的横截面积为S,大气压强为p0,环境温度为T0
①求活塞质量m.
②若要让活塞在气缸中的位置复原,要把温度升到多高?
上一题 下一题 0.0难度 选择题 更新时间:2019-06-20 06:24:56

答案(点此获取答案解析)

解:①以气缸中的封闭气体为研究对象,气体发生等温变化,
初态: p1=p0V1=LS

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阅读理解

    Hundreds of years ago,a Roman army came north from England to make war on Scotland. The Scots,a brave people,loved their country very much. They fought hard to drive the enemy out of Scotland,but there were too many Romans. It looked as if the Romans would win.

    One night,the leader of Scots marched his soldiers to the top of a hill. "We will rest here tonight,my men,” he said. "Tomorrow we will fight one more battle. We must win or we will die."

    They were all very tired,so they ate their supper quickly and fell asleep. There were four guards on duty, but they were very tired as well and also fell asleep one by one.

    The Romans were not asleep. Quickly they gathered at the foot of the hill. Slowly they climbed up the hillside, taking care not to make a sound. Closer and closer they came to the sleeping Scots. They were almost at the top. A few minutes more,the war would be over. Suddenly,one of them put his foot on a thistle(蓟). He cried out and his sudden cry woke the Scots. In a moment,they were on their feet and ready for battle. The fighting was hard but it did not last long. The Scots wiped out the Romans and saved their country.

    The thistle is not a beautiful plant. It has sharp needles all over it. Few people like it. But the people of Scotland liked it so much that they made it their national flower.

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