Now I think I am wrong. I forgot that higher speed makes bouncing more frequent so the effect cancels out. But the horizontal effect is still there. So it is still true that hotter gas in constant volume becomes lighter. Unless something is happening at the walls.
David On Sat, Jun 11, 2011 at 7:58 PM, David Jonsson <davidjonssonswe...@gmail.com > wrote: > Hi > > This obvious fact from hot air balloons and rising smoke is also the case > in constant volume. Just do the math if you can't see what I mean. > > Imagine a ball on lying at rest in a box. This is equivalent of a cold gas. > All pressure from the ball is on the bottom of the box. The weight of the > ball is just added to the box. Now let the ball do very fast bounces up and > down. The box will not weigh as much as before because the ball is also > bouncing on the ceiling of the box with almost as strong impulse as it is > bouncing on the bottom. The box + ball weighs less. The faster the ball > moves the less time it spends between bounces and the less can it's speed > change. Speed change is time multiplied with gravitational acceleration and > the faster it moves the less the speed can increase and decrease between the > bounces. > > The same must be the case for a gas. Gas is just a collection of small > balls. The same must be the case if the box is removed and the gas molecules > bounce against each other. Right? > > I have written before about this on the Internet but only for tangential > motion but today I realized it must also be the case for vertical motion. In > tangential motion the centrifugal acceleration increases and thus makes > balls as well as gas molecules appear as having less weight. > > From the garden of the Stockholm Observatory, > David > > David Jonsson, Sweden, phone callto:+46703000370 > >
