Agen0 Posted September 29, 2005 Share Posted September 29, 2005 Ok, these qestions have been haunting me for a whine and I would like some ansures... soo here they are: 1. I know that "warmth" is the vibrations of molecules/atoms, the faster they vibrate, the warmer it is, but what's sound? Is it also the molecules vibrating? If it is then why does'nt it get warmer when I play loud music and why cant I hear cold and warmth (whell the ansure to that might be that humans can only hear from 20 - 20kHz) 2. How can there be "cold wind"? The wind molecules move at great speed, yet they are cold... 3. When I shake my hand at my face, then the air gets colder, why? I make the molecules move faster by shaking my hand, soo why does it get colder? 4. Is it true that the colder air is, the slower it is sucked out into spece, as the molecules move slower. Link to comment Share on other sites More sharing options...
mezarashi Posted September 29, 2005 Share Posted September 29, 2005 1. Temperature is caused by random movement of the molecules and atoms. There is no noticeable drift velocity. Sound propagates in air by compressing it logitudinally in a periodic fashion. There is a macroscopic displacement every time a wave goes through a particular region. And well due to frictional forces, you will somewhat heat up the air if you played that hard but wave propagation through matter and matter's own kinetic energy are two different things. 2. Wind is "cold" because of convection. It helps take away the heat. So by blowing air on to something you are helping it cool down giving the "illusion" that the moving air is cold. Of course, if there is water on the surface that the wind is being blown on, you get additional heat escaping through the water evaporating. That's why it feels even "colder" when you stand in front of a fan wet. 3. Continued from what I mentioned earlier. With humans, the water evaporation effect is even more emphasized because we sweat. The wind helps take away newly evaporated sweat so that conditions are favorable for even more sweat to evaporate. In order to evaporate, the sweat (water) needs energy. This energy is from your skin's warmth. Thus you cool down and feel cool. 4. I'm not sure at all what you mean by this one. I don't know of any place on Earth where air is being sucked "out into space". o_o Link to comment Share on other sites More sharing options...
Agen0 Posted September 29, 2005 Author Share Posted September 29, 2005 4. I'm not sure at all what you mean by this one. I don't know of any place on Earth where air is being sucked "out into space". o_o Sucked out into space as in into the vacuum outside our atmosphere. For instance a rocket gets a hole in it and the air gets sucked out. Link to comment Share on other sites More sharing options...
Xyph Posted September 29, 2005 Share Posted September 29, 2005 I don't think the Earth is losing atmosphere anymore, although I could be wrong. Either way, though, theoretically the answer to 4 is yes - particles with more kinetic energy will find it easier to escape a gravity well. Link to comment Share on other sites More sharing options...
Agen0 Posted September 29, 2005 Author Share Posted September 29, 2005 I don't think the Earth is losing atmosphere I did not say that. Link to comment Share on other sites More sharing options...
Xyph Posted September 29, 2005 Share Posted September 29, 2005 Ah, sorry. That's what I assumed you meant by this. Sucked out into space as in [b']into the vacuum outside our atmosphere.[/b] Link to comment Share on other sites More sharing options...
J.C.MacSwell Posted September 29, 2005 Share Posted September 29, 2005 Sucked out into space as in into the vacuum outside our atmosphere. For instance a rocket gets a hole in it and the air gets sucked out. The answer is yes, although it is more correct to think of the colder/ lower pressure air escaping slower than it would if it was hotter/ higher pressure than being "sucked out" slower. I would agree with Xyph by the way I originally interpreted the question. Link to comment Share on other sites More sharing options...
Severian Posted September 29, 2005 Share Posted September 29, 2005 2. Wind is "cold" because of convection. It helps take away the heat. So by blowing air on to something you are helping it cool down giving the "illusion" that the moving air is cold. Of course' date=' if there is water on the surface that the wind is being blown on, you get additional heat escaping through the water evaporating. That's why it feels even "colder" when you stand in front of a fan wet. [/quote'] That is true, but is not what is usually meant by a 'cold wind'. A wind can be cold simply because the air is blowing in from a colder region. The air in the wind is literally colder than the air it is replacing. So winds from the north are often cold winds (in the northern hemisphere). Link to comment Share on other sites More sharing options...
Agen0 Posted September 30, 2005 Author Share Posted September 30, 2005 Yes.. whell take alook at my next sentence. For instance a rocket gets a hole in it and the air gets sucked out. Sucked out into the vacuum outside our atmosphere - as in not directly from Earh, but from a space ship. Link to comment Share on other sites More sharing options...
[Tycho?] Posted September 30, 2005 Share Posted September 30, 2005 Yes.. whell take alook at my next sentence. Sucked out into the vacuum outside our atmosphere - as in not directly from Earh' date=' but from a space ship.[/quote'] I doubt temperature would have much of an influence on that. Link to comment Share on other sites More sharing options...
Dave Posted September 30, 2005 Share Posted September 30, 2005 '']I doubt temperature would have much of an influence on that. I would tend to agree on that one. The effects of temperature would be completely negligable as the remaining air was blown out into space. Link to comment Share on other sites More sharing options...
J.C.MacSwell Posted September 30, 2005 Share Posted September 30, 2005 I would tend to agree on that one. The effects of temperature would be completely negligable as the remaining air was blown out into space. If you have the same mass of air, in the same space, the higher temperature will have higher pressure. So it will get "blown out" or escape faster (or will get "sucked out" more quickly if AgenO prefers looking at it that way) Link to comment Share on other sites More sharing options...
mezarashi Posted September 30, 2005 Share Posted September 30, 2005 If you have the same mass of air, in the same space, the higher temperature will have higher pressure. So it will get "blown out" or escape faster (or will get "sucked out" more quickly if AgenO prefers looking at it that way) Since temperature increases pressure in a fixed volume, it would make sense in that respect. I just hope that it is understood by AgenO however that the internal kinetic energy of any gas is not related to any net drift phenomena. My concern here comes from his first post questioning The wind molecules move at great speed, yet they are cold... What the temperature can do is affect things like pressure and air density which will result in convection or winds. Link to comment Share on other sites More sharing options...
swansont Posted September 30, 2005 Share Posted September 30, 2005 The wind molecules move at great speed' date=' yet they are cold...[/quote'] Not really. "still" air at room temperature has an average speed of a few hundred mph. But the average velocity is zero. The effect of evaporation has already been mentioned. Link to comment Share on other sites More sharing options...
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