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Body "falling" sideways

  1. Feb 17, 2015 #1
    I am a writer, and this is the opening scene in a story I'm currently working on. A girl weighing 110 lbs gets sucked across a room, about 50 yards, then hits the wall. Her boyfriend knows that if he doesn't get her into a stasis pod within 10 minutes, she'll be dead from the massive internal injuries. He's the brainy kind, so he thinks of this in physics terms. I need to know about how fast she could have been "falling" and with how much force she probably hit the wall, assuming the force of the suction was a constant.
  2. jcsd
  3. Feb 17, 2015 #2


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    Is this "suction" caused by air blowing or what? That is, what you you MEAN "suction" ?

    If, for example, there was a constant wind, like in a wind tunnel, and it was strong enough to move 110 human 50 yards, and the wall was pretty solid, I'd think it would have to be 150 mph or so wind, in which case, when she hit the wall, if she managed not to die instantly of brain damage, she'd not likely last more than seconds before drowning from the blood due to massive internal injuries.
  4. Feb 18, 2015 #3
    Clearly by mentioning the employment of a "stasis pod" we are in the realm of a science fiction scenario and may guess that the details of the sideway fall force that causes the woman to be injured stems from some exotic situation - perhaps the room was in the circular spinning ring of a space station impacted at its edge by a slow meteor or fast spacecraft and the rotation speed was suddenly changed, or the drive for a spaceship was accidentally engaged without the exotic precautions used to prevent this kind of thing during acceleration...

    There is also the assumption that medical technology is sufficiently advanced that just about anybody can be fixed of any injuries if what is left of them can be contained and preserved in a stasis pod within ten minutes -so I don't understand why the fella needs to assess her fall speed - he already knows he has ten minutes to save her.

    Depending on the story line and the cause of the sideways fall, I think you are free as a writer to make her fall distance, fall time, fall impact, and her injuries consistent with whatever situation you are creating. The critical thing to me is how the fella is going to get her into the stasis pod... he knows he has ten minutes to figure out and execute a plan to save her. So my questions would be:

    - is the sideways falling force over now, or is it still going on (does the fella have to worry about falling, or it that thing over?)
    - where is the stasis pod, and can he bring it to her or must he take her to it?
  5. Feb 19, 2015 #4


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    It's not really possible to say "this speed is fatal" or "that speed is survivable". People have been killed after tripping over their own feet while others have survived falls from a great height. Google found a report of someone falling 22 floors onto the roof of a car. He wasn't even knocked out. He climbed off car and when examined had only broken an elbow. A lot depends on what you hit.

    One approach might be to make the wall padded. It would then be possible to calculate the likely g-force that the person experienced from the speed and thickness of the padding. For example you could assume that the stopping distance is the thickness of the padding. If you don't want to make the wall padded another option would be to have the boyfriend measure the depth of the dent her head made in a metal wall. Use that as an estimate of the stopping distance.

    The deceleration "a" is given by..

    a = U2 /2S


    a = deceleration in m/s2
    U = speed in m/s
    S = stopping distance or thickness of the padding or depth of dent (in meters).

    Experiments using rocket powered sledges in the 1960's showed that people can survive 46g which is about 450m/s2...

    So lets work some numbers. Lets say the person is going 9m/s (20mph) and the padding is 4" or 0.1m thick....

    a = 92/2*0.1
    = 405m/s2

    1g = 9.8m/s2

    so 405m/s2 is about 41g which you might consider is survivable.

    Higher figures have been survived. Google reports that a racing driver called Kenny Black survived a crash during which 214g was recorded - however that was probably the deceleration experienced by his car, his body might have experienced lower g...

  6. Feb 19, 2015 #5


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    Mythbusters, while not necessarily rigidly scientific, have a great deal of practical experience with g-forces. They consider 100g's the break-point, below which someone is likely to survive.
  7. Feb 19, 2015 #6


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    Having access to Tech Level 10 ("poof-you're-healed") technology just a few feet away would dramatically improve how close to death you could come and still recover.

    This also means it gives the OP a lot of wiggle room. Heck, she could have a burst heart and still be put back together.

    Also, I do think it's important to understand just what kind of force is propelling the character. Being sucked against a wall sounds pretty fishy, science-wise.

    (In the awful sequel Alien 3, the pubescent Alien got sucked out through a small hole in the fuselage of a spacecraft. What alien is so frail that a patch of armoured skin 4 inches square could not withstand one atmosphere of pressure? o_O)
  8. Feb 20, 2015 #7
    The problem with your question is all the parts needed to give an answer are the parts you left out.
    A human body has no maximum speed it can go by itself, besides light speed.
    However how fast a body can move and survive is dependent on 2 factors, how fast, and in which direction, and if I remember right speed going one way is like mach 20, but another it's mach 10, and going another it is again different.
    Whether a body can survive smashing into something, again it depends on how one takes the impact and such factors... likewise it depends on how much damage you want to deliver. Do you want the body to explode? Do you want them to have broken bones? Just bruised?

    So you have 3 things to consider
    Force of initial hit
    Speed of flight
    Force of impact

    I'm assuming you want everything from Force of Impact which you can get from how fast someone is travels when they jump off a building and how much damage it is.
    The big problem is that that relies on acceleration over time and I would assume you're in a room with fairly close walls which means some of the other 2 things need to be considered... Because if the wall is 10 feet away you are not going to suddenly accelerate to 100mph for example without something hitting you. Unless you're in a space ship, which would then cause everything else to have the same problem.
  9. Feb 20, 2015 #8


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    Durakken - the OP mentions 50 yards.

    When there is an air leak in a spacecraft it's traditional to have an alarm and perhaps a flashing strobe light go off. The strobe light could be used as a device to estimate the girls speed. For example as she flies past the strobe flashes might make her appear briefly stationary against the background. If you know the time between flashes and the distance she appeared to move between them you can estimate her speed. For example if the flashes are one per second and in that time she appeared to fly past 4 port holes then if the port holes are 2 meters apart she travelled 8 meters in one second or 8m/s.
  10. Feb 20, 2015 #9
    The problem with the scenario is you have 2 people in the same room, one being affected and the other isn't.
    Further, assuming we're in space and they're being blown out a hole I'm pretty sure it's not enough to slam a person into the wall at that high of a speed.
    This means she has to go from 0 to 30+ mph in 50 yards... 150 feet. Meaning she has to have gotten to the end point in about 3 seconds or less... or an acceleration larger than 4.4704 m/s^2... which though I can't confirm should probably be about half 1/2 of terminal velocity so whatever you'd feel when you're at that should give you your answer to how bad this would be... or something like that I'm bad with math a lot of times so someone else should check this all.
  11. Feb 21, 2015 #10


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    I make the required acceleration much less than that...

    V2 = U2 +2as
    a = (V2-U2)/2s

    U =0 (standing start)
    V = final velocity say 30mph or 13.5m/s
    s = distance = 50m
    a= 1.82 m/s2

    Gravity is 9.8 m/s2 so the required acceleration to reach 30mph isn't huge.

    Her mass is 110lbs or 50kg so the required force is..

    F = ma = 50 * 1.82 = 90N

    90N is about 20 lbs force.

    In reality it I suspect the acceleration wouldn't stay constant for the whole 50m as the force of the air would reduce.
  12. Feb 21, 2015 #11


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    Has anyone noticed that the OP appears to be a drive-by?
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