On Tue, Feb 16, 2016 spudboy100 via Everything List < [email protected]> wrote:
> > > When I think of energy, I think of movement, or flow. That's one form of energy, and the amount of energy depends on the mass of the moving object and its velocity but it turns out that of the two velocity is more important; double the mass and the energy doubles but double the velocity and you have 4 times the energy. > > > or flow Flow is a bit different. The ability of a flow of air to do work on a window, that is to say cause damage to the window, is proportional to the cube of the wind speed not the square. It's true that if you double the speed each individual oxygen and nitrogen molecule would have 4 times the energy, but you'd have 2 times as many molecules pass through a unit area in the same amount of time and twice as many particles each with 4 times the energy makes 8. So a 126 mph wind would produce twice as much damage as a 100 mph wind and a 144 mph wind 3 times as much and a 159 mph 4 times as much. Or you can think about it this way, if the wind is gentle it will exert a force on the window, but it's work that causes damage not force, and work is force over a distance. The gentle wind does not move or distort the window so no work is done on it and it suffers no damage. A faster wind will move the window, and that means it will do work on it, and that means it will shatter it. > When I think of matter, I think of bound things like atoms or molecules, where the flow is very slow. Air is made of molecules but they are not moving slowly. In a box of air at room temperature the molecules in the box are moving at about 1,200 miles per hour, but the molecules are all moving in different directions. For the energy in that box to actually do something, for it to do work, the molecules must move in the same direction, and there are ways to do that with heat engines but the second law of thermodynamics tells us you can never do that with 100% efficiency, some of the molecules will always be moving in the wrong direction and energy will be wasted. John K Clark -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected]. Visit this group at https://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout.
