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I Make Water Behave Like In Space -- Video

  1. Mar 27, 2016 #1
    Hi,

    just came across a video on CNN showing how to make water behave like it would in space:
    <link to video deleted>
    My question about that video is:
    what height do i need to get a free fall time of 10 sec?

    best regards
     
    Last edited by a moderator: Sep 4, 2016
  2. jcsd
  3. Mar 27, 2016 #2

    DaveC426913

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  4. Mar 27, 2016 #3
  5. Mar 27, 2016 #4
    You would need one seriously tall building. After a short google search I can tell you that there is only one building in the USA that would be tall enough. Nothing comes even close, if you are in Europe. I guess you will want to rent a helicopter then :).

    You can find the actual number from one of the four kinematic equations, used to describe bodies moving with constant velocity or acceleration. Namely this one:

    x=x0+v0t+½⋅at2,

    where: x- position after time t, x0-initial position, v0- initial speed, t- time, a- acceleration.

    Plug in the values for the variables and you have your answer. You have all the information you need (or can google for it). Let me know if you need more tips.

    Although this is neglecting air resistance, so in the real world you would need less.
     
  6. Mar 27, 2016 #5

    DaveC426913

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    You should check the specifics of this or other calculators for a more accurate prediction for your setup. For example, this one assumes air resistance equivalent to a skydiver, which would be higher than for your more compact device. And the actual mass of your device has a pretty strong influence as well. Changing mass from 10kg to 100kg alters the distance by dozens of metres.
     
  7. Mar 27, 2016 #6

    DaveC426913

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    BTW, I am very skeptical of that video. Too many things seem wrong.
    Though the principle is sound.
     
  8. Mar 27, 2016 #7
    The box appears to be foam plastic, so the air resistance/weight would be significant. The water would not experience 0 g.
    EDIT: Here's another from the same folks <link to video deleted>
    :rolleyes:
     
    Last edited by a moderator: Sep 4, 2016
  9. Mar 29, 2016 #8
    That one look even more faked. :)
    It behaves like it's attached to a string.
     
  10. Mar 30, 2016 #9

    DaveC426913

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    Totally.
    Between 00:37 and 00:47 it's not even pointing in the direction it's moving. Just as it would if it were suspended on a string.

    Busted.

    airplane.jpg
     
    Last edited: Mar 30, 2016
  11. Mar 31, 2016 #10

    mfb

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    Which tells you that air resistance is not negligible - so the inside would not be a zero-g environment. It should work fine for a second or maybe two, but for more you want evacuated towers (up to ~8 seconds if they shoot the stuff up first). Even longer zero-g periods are possible with airplanes (~25 seconds), suborbital rockets (minutes) and finally orbital rockets (decades++).
     
  12. Sep 4, 2016 #11

    DrClaude

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    Staff: Mentor

    You did not come across this on CNN.

    Thread closed.
     
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