Shredex 0 #1 December 28, 2012 Will you fall slower in hot or cold air? Cold air is more dense then hot air, so you think you would fall slower due to the drag on the higher density. But at the same time, hot air rises and cold air descends... So which is it? Quote Share this post Link to post Share on other sites
jakee 1,564 #2 December 28, 2012 QuoteBut at the same time, hot air rises and cold air descends... Localised and relative. Air doesn't all go up during the day and come back down at night.Do you want to have an ideagasm? Quote Share this post Link to post Share on other sites
theplummeter 15 #3 December 28, 2012 You fall faster in hot air. Hot air is less dense so you have to fall further per parcel of time to hit the same number of air particles. Quote Share this post Link to post Share on other sites
jakee 1,564 #4 December 28, 2012 He's got that part already, he just needs to think a little more about meteorology.Do you want to have an ideagasm? Quote Share this post Link to post Share on other sites
labrys 0 #5 December 28, 2012 Quote Cold air is more dense then hot air, so you think you would fall slower due to the drag on the higher density. But at the same time, hot air rises and cold air descends... Today's new word is "variable" Owned by Remi #? Quote Share this post Link to post Share on other sites
kallend 2,112 #6 December 29, 2012 QuoteWill you fall slower in hot or cold air? Cold air is more dense then hot air, so you think you would fall slower due to the drag on the higher density. But at the same time, hot air rises and cold air descends... So which is it? The hot air can't all rise at the same time now, can it? THINK!... The only sure way to survive a canopy collision is not to have one. Quote Share this post Link to post Share on other sites
Remster 30 #7 December 29, 2012 Quote...... THINK! Actually, I'm going with "Think less, jump more".Remster Quote Share this post Link to post Share on other sites
JohnMitchell 16 #8 December 29, 2012 Quote THINK! That's asking a lot of us, Doc. Quote Share this post Link to post Share on other sites
kallend 2,112 #9 December 29, 2012 Quote Quote THINK! That's asking a lot of us, Doc. I would hope ATC folks think occasionally.... The only sure way to survive a canopy collision is not to have one. Quote Share this post Link to post Share on other sites
almeister112 0 #10 December 29, 2012 I would imagine most people would see an increase in fallrate when it's colder. We tend to bulk up with winter clothing under jumpsuits, making them tighter and reducing drag, so I'd think that would be a much larger effect than air temperature itself. That's just coming out of my ass, though; that whole "science" thing is hard. Quote Share this post Link to post Share on other sites
dream2fly 0 #11 December 29, 2012 Assuming EVERYTHING is constant except for air temperature, you will fall faster in hot air and slower in cold air because the drag force will decrease with a decrease in air density, and air density will decrease with a decrease in air temperature. Force of drag = 0.5 X density of fluid (in this case air) X velocity^2 X Cd (drag coefficient) X A (reference area) Sources: http://en.wikipedia.org/wiki/Drag_(physics) http://www.engineeringtoolbox.com/air-properties-d_156.html Quote Share this post Link to post Share on other sites
Shredex 0 #12 December 30, 2012 The reasoning I ask, is because normally in a track I can get to a good 82mph vertical speed with the lowest being 79 and an average of 86. But last weekend it was a very cold day and I had one heck of a tailwind pushing me along and yet I couldn't fall slower then 95mph. It confused me...still is... Quote Share this post Link to post Share on other sites
jakee 1,564 #13 December 30, 2012 QuoteBut last weekend it was a very cold day and I had one heck of a tailwind pushing me along and yet I couldn't fall slower then 95mph. Why is the tailwind relevant? (And you probably just had a less good jump than normal.)Do you want to have an ideagasm? Quote Share this post Link to post Share on other sites
kallend 2,112 #14 December 30, 2012 QuoteThe reasoning I ask, is because normally in a track I can get to a good 82mph vertical speed with the lowest being 79 and an average of 86. But last weekend it was a very cold day and I had one heck of a tailwind pushing me along and yet I couldn't fall slower then 95mph. It confused me...still is... How was the fall rate measured? GPS or barometric altimeter? That could have an influence on a cold day.... The only sure way to survive a canopy collision is not to have one. Quote Share this post Link to post Share on other sites
Shredex 0 #15 December 30, 2012 Alti-Track was used. Quote Share this post Link to post Share on other sites
theonlyski 8 #16 December 31, 2012 QuoteAlti-Track was used. I wouldn't consider that a very reliable form of measurement. To answer your previous question, I fall at the same speed, just seems MUCH longer when it's fucking freezing."I may be a dirty pirate hooker...but I'm not about to go stand on the corner." iluvtofly DPH -7, TDS 578, Muff 5153, SCR 14890 I'm an asshole, and I approve this message Quote Share this post Link to post Share on other sites
billvon 3,080 #17 January 2, 2013 >I would imagine most people would see an increase in fallrate when it's colder. We >tend to bulk up with winter clothing under jumpsuits, making them tighter and reducing >drag . . . ?? More clothing increases drag. It's pretty common to have bigway fallrate problems on the first dive of the day when people add sweaters and thermals. Cold air is also more dense, and this decreases fall rate BUT it decreases fall rate for everyone and thus is not a factor for relative work. Quote Share this post Link to post Share on other sites
skyjumpenfool 2 #18 January 2, 2013 I tend to notice the difference more when landing my canopy's. Birdshit & Fools Productions "Son, only two things fall from the sky." Quote Share this post Link to post Share on other sites
rehmwa 2 #19 January 2, 2013 Quote I tend to notice the difference more when landing my canopy's. it also seems easier to absorb air through my skin on hotter days (for breathing in freefall) this question is one about the variability of a very minor factor in freefall speeds - the first question should really be "does the variability in air density even have enough effect to overcome the natural variability of freefall speeds" - i.e., colder air = more resistance = slower terminal v with all other things held constant - which they aren't normally. But is it really even noticable when you realize that all other things aren't held constant from jump to jump, let alone on completely different temperature days? ... Driving is a one dimensional activity - a monkey can do it - being proud of your driving abilities is like being proud of being able to put on pants Quote Share this post Link to post Share on other sites
skyjumpenfool 2 #20 January 2, 2013 I'd agree with Bill for the free fall portion of this. But I think it's very noticable landijng a canopy. JMHO...Birdshit & Fools Productions "Son, only two things fall from the sky." Quote Share this post Link to post Share on other sites
potatoman 0 #21 January 3, 2013 Go and do the jump another 10 times, and then you compare. Alti issue, clothing, your body position, the "tailwind", hehe... Did you check on your footage to see if you did not have a bootie that came off ie less drag. Anyways, next time, screw tracking to check your speed, try speedskyjumpin.You have the right to your opinion, and I have the right to tell you how Fu***** stupid it is. Davelepka - "This isn't an x-box, or a Chevy truck forum" Whatever you do, don't listen to ChrisD. Quote Share this post Link to post Share on other sites
