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发表于 2009-12-25 18:04:45
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香港理工大学教授讲解中国大陆以前的机车牵引车厢的原理:
This train I normally I remember you take and we call with the car, right, car 1, car 2, car3. And become a Canton I and you cannot see this, but in mainland China sometimes you can see the connection between this car and this car is some steel chain. Ok ok ok.And this is where the driver needs chains. Ok and you now you so I want to talk. When the driver moves this, ok, if they want to physical, for example this direction what they do? They go to this direction first. They push in there so that what? So that between this car and this car you will have to change something like this.There is no force between this and this and then we go back to go along this direction and then what? At any moment, at any moment, he has to pull one car only.Ok, pull this one and later, ok, this one moves and then this chain becomes straight and then, ok, another moment this car and then another moment this car he does not have to pull all these cars at the same time and why is that? Why he does not want to move all these cars because you know what the static,what friction is big. That's why I want to put this picture in lecture ten or lecture what. Anyway that's idea and the one you put it on dislocations, the motion of dislocations that exactly the same story, ok, same idea, same idea. You pull one car at any moment, you are not pulling all of them all of them at the same time, ok, so now the car is absent. You are just trying to change a few atoms at any time, you are not trying to change all of them at the same time. Ok, so that's why you don't have to put huge force on the material in order to reduce a plastic, right.
[ 本帖最后由 super_astronaut 于 2009-12-26 14:00 编辑 ] |
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