Skydiver plans freefall from 25 mi

Discussion in 'General Chat' started by blackwood, Aug 13, 2007.

  1. no that wouldnt be "his" terminal velocity if the definition of "his" is him and the suit he is wearing only. But i see what you are getting at.

    Terminal velocity isnt usually meant to apply to a guy and his parachute.
  2. It's meant to apply to whatever is moving. Could be a car or an airplane at Vmax. Could be a skydiver with and without a deployed chute.
  3. burner is only right by a technicality. he is still though, of course, an idiot

    he WILL technically hit terminal velocity, but that velocity will change throughout his entire journey, so in that respect; Yes he will hit terminal velocity

    although i think burner didnt think that through that far and assumed his velocity would stay constant, therefore weirdengine.jpeg was quickly dispatched and the situation was defused.
  4. #54 Orange F1LM, Aug 13, 2007
    Last edited by a moderator: Apr 25, 2016
  5. #55 blackwood, Aug 13, 2007
    Last edited by a moderator: Apr 25, 2016
    Sadly, one of the proprietors of the major mars and moon conspiracy websites (and co-author of a related book) is a friend of mine...
  6. #56 Atomic2, Aug 13, 2007
    Last edited by a moderator: Apr 25, 2016
  7. It doesn't even make sense. What does any gain from? Oh no, Mars is red so the Europeans aren't going to try and go there!!!
  8. #58 blackwood, Aug 13, 2007
    Last edited by a moderator: Apr 25, 2016
    No, they believe that Mars used to be inhabited but that a major climate catastrophe rendered it uninhabitable.

    NASA/USG are covering it up because of the panic it would cause.

    Or something like that.
  9. its not a secret that mars ISNT really red, it just has many rusty deserts which blow into the air and often make it look red. they are also a prime place to land a rover. on clear day in mars though, the sky is actually blue IIRC.

    its just stupid to think NASA is covering this up
  10. If we were to assume gravity and temperature were constant (which they wont be), and that the atmosphere is an ideal gas (which it isn't), that terminal velocity of a human head first is 200 mph (89m/s), and that the average man weighs 75 kilos, we can do this in two steps.

    One, find the combined Cd and A for a human being:

    mg = 1/2pv^2CdA
    CdA = 2mg/pv^2 = 0.144

    Two, we combine several equations

    p = p(0)exp([-g(0) x M(0) x h] / [R x T])
    mg = 1/2pv^2CdA

    v can be expressed as 9.81t, and h can be expressed as (40,234 - .5x9,81t^2), 40,234 being 25 miles in meters.


    mg = 1/2[p(o)exp([-g(0) x M x (40,234 - .5x9,81t^2)] / [R x T])][9.81t]^2[0.144], and solve for t:
    90 seconds?
  11. Although I'm probably over my head and that was probably wrong.
  12. #62 Orange F1LM, Aug 13, 2007
    Last edited by a moderator: Apr 25, 2016
    ok guys since you brought it up and are calling me a liar, sorry i had to do this in here

    heres a nasa picture, look at the colors in the sun dial

    here is the real thing, on earth

    if you cant see a difference you are color blind. how much clearer do you need it?

    Anyone here a photshop expert?

    Can you 'fix' this image so that the colors are correct on the sundial?
  13. If you're describing what terminal velocity is, rather than how to find terminal velocity, I don't see whats so wrong with writing it that way (with whole equations for force on both sides).

    Also, I only meant it as 'relatively' constant. It wont change as much as the density of the air he's transversing.
  14. There's nothing wrong with it. But terminal velocity is a velocity, so if that's what you're describing, it would seem prudent to isolate the V.

    You (probably) wouldn't describe force as follows: a=f/m

    But don't mind me. I'm just being argumentative for the sake of it.
  15. Question: Assuming he free falls head first, would any irregular pressure/force snap his neck unless secured?

    Im not very knowledgeable on physics, but if there were a force extreme enough in his descent.
  16. #66 blackwood, Aug 13, 2007
    Last edited by a moderator: Apr 25, 2016
    Nobody is claiming that the pictures don't have different color temperatures. They're claiming that the colors weren't altered for the purposes of deceiving the public as to the color of the sky as seen from mars.
  17. I wrote to demonstrate, to not calculate
  18. For sure, certainly may have not been trying to deceive the public, but still seems pointless to publish the wrong colors such that blue could change to bright pink and green could turn to dark brown.

    THey would have been better off bringing up a Nikon Coolpix in that case for a more accurate color calibrator.
  19. #69 Atomic2, Aug 13, 2007
    Last edited by a moderator: Apr 25, 2016
    pretty much, because the "conspiracy theorists" are using this to claim nasa is covering up life somehow...
  20. Peace.

    But isolating V would have at least somewhat curbed that clusterf_ck of a calculation above :p

    Incidentally, what are you doing here?

    p = p(0)exp([-g(0) x M(0) x h] / [R x T])

    Is that a gas density equation? I'm not familiar with it.

  21. It is, or it's supposed to be. I didn't remember most of it though, so I just ripped it off Wikipedia. I didn't feel like I wanted to spend the time needed to czech everything, when it's just an Internet argument and not a real problem.

    Which is why I think it's horribly incorrect, but more correct than Burner.
  22. The idea is sound. But it's extremely hard to follow.

    Solve for V. Then run a simple kinematic computation to find out how long to reach V.

    SUM F=m*SUM a
    at terminal velocity, a=0
    SUM F=0




    Make your assumptions for the 'constants'.
    Plug and chug to get V and then solve for time.

    note, I didn't check my algebra, so there could very well be a mistake.
  23. Assuming everything is constant, which it isn't. He could decide to go head first for instance after already being at terminal velocity, then he would no longer be at his terminal velocity.

    This statement is too generalized for you to be an asshole about.
  24. 'then he would no longer be at his terminal velocity'

    until he is again.

    It's important to note that his drag will decrease after M=1, instantaneously increasing TV.
  25. i think the highest recorded for him was closer to 600mph

Share This Page