题目内容
如图均匀薄壁U形管,左管上端封闭,右管开口且足够长,管的截面积为S,内装有密度为r的液体。右管内有一质量为m的活塞搁在固定卡口上,卡口与左管上端等高,活塞与管壁间无摩擦且不漏气。温度为T0时,左、右管内液面等高,两管内空气柱长度均为L,压强均为大气压强P0,重力加速度为g。现使左右两管温度同时缓慢升高,在活塞离开卡口上升前,左右两管液面保持不动,试求:
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250007423822005.png)
(1)右管活塞刚离开卡口上升时,右管封闭气体的压强P1;
(2)温度升高到T1为多少时,右管活塞开始离开卡口上升。
(3)温度升高到T2为多少时,两管液面高度差为L。
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250007423822005.png)
(1)右管活塞刚离开卡口上升时,右管封闭气体的压强P1;
(2)温度升高到T1为多少时,右管活塞开始离开卡口上升。
(3)温度升高到T2为多少时,两管液面高度差为L。
(1)P0+
(2)T0(1+
)(3)
(P0+
+rgL)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000742398550.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000742414647.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000742429581.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000742398550.png)
试题分析:(1)活塞刚离开卡口时,对活塞
mg+P0S=P1S 得 P1 =P0+
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000742398550.png)
(2)两侧气体体积不变 右管气体
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000742476475.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000742492417.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000742414647.png)
(3)左管内气体,V2=
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000742507393.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000742398550.png)
应用理想气体状态方程
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000742694617.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000742741640.png)
得 T2=
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000742429581.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000742398550.png)
![](http://thumb2018.1010pic.com/images/loading.gif)
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