Reply to: Somebody’s about to jump off the building

[Sysman]

A friend of mine’s a journalist for NOS Radio 2; he says there’s an unwritten rule in the Dutch press to not give press attention to such suicides to avoid provoking others who might be considering the same thing. Decide for yourself on the logic of that. I also know that when people jump in front of a train, which happens quite often, the train company announce it neutrally by saying there was an ‘aanrijding’ or ‘collision’. You could get the impression that trains are constantly crashing in Holland, but in reality they’re saying there was a suicide.

The same happens in Switzerland except they use another euphemism. Many know what they mean though.

[Sysman]

My grandad worked on the railways for years, he was deputy station master at Paddington in the late 60's.

One of his jobs, along with kicking in the doors of toilet cubicles and dragging out the junkies who'd od'd in there, was helping recover the bodies after a "one under". By the time the trains had finished with them they came out in chunks, not entirely dissimilar to the large vacuum packed joints you get in a supermarket.

I recall a story told by an ex-Met copper from the days of steam trains. The fire brigade was busy putting out a fire on a railway track caused by red hot coals being spat out of a train funnel.

Two trains came past at full speed in opposite directions with the firemen standing in the gap in between the tracks.

Same result apparently.

[Gibbon]

Did you spill your pasta?

No I was far too south for pasta. Try penguin burger.

[Gibbon]

Ah I see. Is this because lower temperature = higher density or is it more complex than that?

More complex. Varying density doesn't really come into play in a gas.

"An analysis based on conservation of mass and momentum shows that the speed of sound a is equal to the square root of the ratio of specific heats g times the gas constant R times the temperature T.

a = sqrt [g * R * T] "

[Churchill]

Wrong. Speed of sound decreases with height due to lowering temperature, until you hit a temperature inversion higher up.

I know this as I have travelled through the sound barrier.

Did you spill your pasta?

[suityou01]

Oh FFS.

Ok, here we go.

I was referencing the bloke who was going to attempt the highest freefall jump. It was estimated that he would break the sound barrier on his way down.

Doodab obviously understand what I meant.

SY01, stick to wringing your hands like a fairy as your project turns to ratsh!t.

chillax dude

[doodab]

Wrong. Speed of sound decreases with height due to lowering temperature, until you hit a temperature inversion higher up.

I know this as I have travelled through the sound barrier.

Ah I see. Is this because lower temperature = higher density or is it more complex than that?

[Churchill]

that is what supersonic means.

HTH

Oh FFS.

Ok, here we go.

I was referencing the bloke who was going to attempt the highest freefall jump. It was estimated that he would break the sound barrier on his way down.

Doodab obviously understand what I meant.

SY01, stick to wringing your hands like a fairy as your project turns to ratsh!t.

[TimberWolf]

At terminal velocity, the drag force is by definition equal to the gravitational force. Gravity is slightly weaker at altitude because you are further from the earth, but at those sorts of heights it's not going to be that much weaker and the lower air density would dominate.

Yes, at equilibrium (terminal velocity) the drag force is the same at any height - equal and opposite to your weight. At higher altitude free-fall, prior to equilibrium, you accelerate faster. Ergo there is less of a drag force acting on you at higher altitudes, even though you accelerate and travel faster through thinner air. So limbs do not appear to be in any more danger of being shaken off at greater height as a consequence of attaining greater speed than at lower altitudes. Once at equilibrium (terminal velocity), the drag forces are the same at any height.

[suityou01]

Did that chap break the sound barrier?

that is what supersonic means.

HTH

[Gibbon]

Apparently not. Of course the speed of sound increases with the decreasing air density so it's quite a bit higher at altitude.

http://www.newscientist.com/article/...-freefall.html

Wrong. Speed of sound decreases with height due to lowering temperature, until you hit a temperature inversion higher up.

I know this as I have travelled through the sound barrier.

[doodab]

Did that chap break the sound barrier?

Apparently not. Of course the speed of sound increases with the decreasing air density so it's quite a bit higher at altitude.

http://www.newscientist.com/article/...-freefall.html

[Churchill]

Indeed.

Terminal velocity can be supersonic if you're high enough up.

As in falling from a balloon at 100,000ft*.




*don't try this at home.

Did that chap break the sound barrier?

[doodab]

Seems unlikely to me, but I suppose there is an outside chance your limbs might shake off. Your terminal velocity would of course be lower than "hundreds of miles an hour" at lower altitudes, and at higher elevations would be greater because the atmosphere is thinner, but drag forces would also be less at height and I can't be arsed to do the calculations.

At terminal velocity, the drag force is by definition equal to the gravitational force. Gravity is slightly weaker at altitude because you are further from the earth, but at those sorts of heights it's not going to be that much weaker and the lower air density would dominate.

[Churchill]

Which is where the Terminal bit in Terminal Velocity comes from

Err, no it ain't. But good one.