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And so what happens when we remove these stops is that the piston slams up against the next pair of stops.
把挡板移开后活塞会,向上移动直道第二个挡板处。
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I like the Pistons, the Tigers, the Lions, Red Wings.
我喜欢活塞队，虎队，狮队，红翼队。
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Well, we start out with our usual system, and we have a bunch of little pebbles on it.
还是那个系统，活塞上面放了很多小石子。
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The piston has a cross-sectional area, a, and the force pressure is force per volume area.
我们以活塞系统为例，来说明膨胀功。
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So the force that you're pushing down on here is the external pressure times the area.
或者压缩功的概念,在活塞上施加压力。
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So initially, we're going to have our piston, there's the plug sitting here.
所以一开始，这是个活塞，这里是个节流阀。
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If I stop, if I move slowly, if I move more slowly then these two will want equilibrium.
如果我停下来，如果我缓慢地移动活塞,非常缓慢，结果这两个压强会平衡。
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And so we know the force for a particular mass, and we know the area of the piston.
我们知道每个质量对应的力，也知道活塞的面积。
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V2 Now we could put stops here at V2, but this piston would just kiss the stops.
现在我们可以把挡板放在这里，这时体积是，活塞会刚好碰到挡板。
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So it's going to shoot up until the internal pressure and the external pressure are in equilibrium.
活塞将上,移直到内外,压强达到平衡。
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We have a piston. We have a pair of stops.
这有一个活塞，两个挡板。
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So if delta v is negative, in this case delta v is negative, OK, delta v is negative, pressure is a positive number, negative times negative is positive, work is greater than zero.
也就是当活塞,压缩气体的时候，做的功是正的，按照这一规定,我们需要在这里，加上一个负号，这是习惯规定。
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to take my cylinder now, and the external pressure and the internal pressure are not going to be I'm going to start with my cylinder here, I'm going to put little pegs here so it doesn't fly up.
活塞内外的，压强不相等,我们在,放上插销，以防止活塞。
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That's going to drive the wheels.
这是发动机的活塞。
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We have two weights on it.
放两个重物在活塞上。
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It's not doing as much work.
活塞上的力。
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The car is going to go forward.
活塞上升。
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so we know how to do this, and we know this thing when it hit these stops, v2 the pressure with p2, and the volume was V2.
所以我们知道怎么计算，当活塞到达这两个挡板时，压强是p2，体积是。
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Then you put two pistons, one on that side here and one on this side here, and the external pressure here, we're going to call that p1.
接下来我们放进两个活塞,一个在这，一个在这,这变外界的压强为p1；
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So I've got, this piston here is compressed, and I slowly, slowly increase the volume, drop the temperature.
这样，这个活塞就被压缩了，然后我再很慢很慢地增加它的体积，降低温度。
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So we remove the stops, and the piston moves up, and now we remove one of these weights.
我们移走挡板，活塞向上移动，移走一个重物。
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We have a weight on the piston, and that weight is chosen so that p2 it acts as though p external is equal to p2.
让活塞上放一重物，让它的效果刚好,等同于外压强。
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Here there's an expansion going on, so the system is doing work to the external world.
这里发生了膨胀,所以系统对外界做功，活塞被推出来。
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So, the piston moves up again, one weight.
活塞再次上升。
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Then I'm going to release these little pegs here and my piston is going to shoot up now p1 because p2 is less than p1.
现在移开插销,活塞就会往上冲,因为p2小于。
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Our piston on the right side here fully out, and the piston on my right side, your left side, fully inside. There's no gas p1 on that side here. So there's p2 sitting here.
左边的这个活塞完全在外面，而右边的左边的这个活塞完全在里面，这边没有一点空气,这边是P2，这边是。
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