SpaceShipOne in outer space video

hmmmm did not know this.

I never bothered to see what it was in the same medium (IE air at different temps)

they why is sound faster in steel than air even at the same temp ?

Computations

At pressures or temperatures where air does not behave as an ideal gas there'll be nobody alive to argue the point.

Nope. Why do you have such a hard time with the concept of "irrelevant"?

I understand quite well that (1) irrelevant discrepancies do not render a relationship exact, and (2) your idea of irrelevant may be quite different from someone else's, particularly someone capable of precision measurements.

Steven P. McNicoll wrote:

I don't think you do.

Chris, I too was taught in my physics class many decades ago that SOS in air was based on density. This same teacher and I got into an issue of fatter tires on cars not providing more traction. I.e. he said that fat tires did not provide anything other then looks. I guess all the race car engineers are wrong.

he used the standard fish scale pulling a red brick on both the fat and the skinny side accross a wooden lab table showing the same about of force required.

If he had used a block of tire rubber weighted down on an asphalt surface, he might have seen the difference.

anyway, I found this that explained it to me as Steven just know woke me up to this most interesting fact.

So, what you're saying is that atmospheric pressure is constant from 36K to 70K feet?

Doug I'll never correct Tod again....

thankyou for the info. no time right now to read it but I saved it locally and will read it (now I am deadly curious about it :-)

does not pressure effectively deal with density in this scenario ? (I am trying to understand this :-)

IE squeeze more air in a fixed amount of space and that space IS more "dense" than the same volume with less atmosphere in it ?

That's where I was going with 100% vs 0% humidity and smog. (I'm not the argumentitive type.)

He is correct, for a STATIC friction surface. The weight of the car or brick remains the same, thus the force on the surface remains the same. The smaller surface has a higher force per square unit area and the larger surface has a smaller force per unit area. The two different forces are canceled out by the relationship of the unit area to the friction. In other words, the smaller surface area has less friction, but more force per square inch and is exactly equal to the larger surface having more friction but less force per square inch.

However, care tires are dynamic. The friction changes as the tires heat up but more importantly, the torque imparted to the tire causes a higher load in the front of the tire. (ever see the tires on a dragster "wrinkle?) A small tire must have higher pressure. Higher pressures "stiffen" the tire, not allowing it to transfer the torque to the friction area.

That's only part of the reason. The Bowden/Tabor model of friction applies to most things, but doesn't really apply very well to elastomers.

I realize I'm getting old when I can recall attending lectures from both Bowden and Tabor. Tabor was my lab intructor in freshman physics.

yep, thanks for that explanation. I figured out years ago something different , but similar.

It's nice to hear the true reason.

he just didn't like Race Cars BTW.