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Variation of gravity in a Rotating SpaceStation

  1. May 23, 2012 #1
    This is very simple question, and i just need a 2nd opinion.

    We have a Space Station (preferably a torus) with angular velocity ω and radius r. We have a car inside which OPPOSES the angular velocity and moves with the speed ωr . So, will the gravity felt in this car be Zero? Or will it be something else?

    If we replace the car with Usain Bolt, and ask him to run at the speed of ωr , opposing Angular velocity, then, what will be the change in this case?
     
  2. jcsd
  3. May 23, 2012 #2

    A.T.

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    Yes.

    Nothing. Both will have problems propelling themselves at such a speed, because they will loose traction at the outer wall.
     
  4. May 23, 2012 #3

    tiny-tim

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    in case you're wondering …

    in the rotating frame of the spaceship, there is still a centrifugal force on the car of mΩ2r outward, but there's also the velocity-dependent Coriolis force of 2mΩ2r inward, net force of mΩ2r inward, supplying the centripetal acceleration which explains why the car appears to be rotating with speed Ωr even though there's no reaction force from the "floor" of the spaceship! :biggrin:
     
  5. May 23, 2012 #4
    Assume that the station is rotating to re-create gravitational effects on Earth.
    ie the rotation is such that a 1kg mass placed on bathroom scales on the 'floor' of the station registers 10N
    In the context of this post can anyone explain what the reading on bathroom scales would be when
    a) a 1kg mass is placed on bathroom scales placed in the car when it is 'staionary'
    b) a 1kg mass is placed on bathroom scales placed in the car when it is being driven around the space station....what happens to the reading.... greater? smaller, .... the same?
     
  6. May 23, 2012 #5

    A.T.

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    That is answered in the question, isn't it? 10N
    Depends in which direction and how fast it drives, the centrifugal force will be modified by the Coriolis force.
     
  7. May 23, 2012 #6
    Absolutely correct for the first part.
    so... suppose the car is travelling at the same speed as the ring when it is simulating gravity.... what will the bathroom scales read???
    (in each direction)
     
  8. May 23, 2012 #7

    A.T.

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    0N for opposite direction and 20N for outrunning the rotation
     
  9. May 23, 2012 #8
    if you are standing in such a space station how can you tell which way it is rotating?
     
  10. May 23, 2012 #9

    A.T.

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    You just proposed the experiment that tells you the direction. If you mean just by standing still, you can't. But if you can move your arms, the Coriolis force will tell you how it rotates.
     
  11. May 23, 2012 #10
    So if I am standing 'still' in this space station I cannot tell which way it is rotating unless I use the coriolis force on my arms ?? How will the coriolis force reveal the direction of rotation.?
     
  12. May 23, 2012 #11

    A.T.

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    Just like in your scales example. You can do a similar test by swinging your arms and see which way they appear heavier. Maybe while holding a heavy object in your hand.
     
  13. May 23, 2012 #12
    That is not an acceptable answer !!!! wave your arms around.... come on
    HOW can you determine, 'in a physics way', which way the station is rotating?
     
  14. May 23, 2012 #13
    That is 'in a physics way.' If you mean in a controlled way, put to accelerometers (to measure gravity) into two cars, have them move in opposite directions, see which one measured the least acceleration.
     
  15. May 23, 2012 #14
    'Accelerometers to measure gravity'.... that is what I mean by bathroom scales !!!!
    How would they tell you the direction of rotation??....if they are on a moving car?
     
    Last edited: May 23, 2012
  16. May 23, 2012 #15

    A.T.

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    See post #7
     
  17. May 23, 2012 #16
    I could not fully understand post 3, does your post agree with post 3?
    I have to explain these things to 16 and 17 year old students.
    Any help in this are would be valuable.
     
  18. May 23, 2012 #17

    A.T.

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    Yes.
     
  19. May 23, 2012 #18
    If you hold a ball in your hand in this space station and let it go what will happen?
     
  20. May 23, 2012 #19

    A.T.

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    It will accelerate according to the sum of centrifugal and Coriolis forces.
     
  21. May 23, 2012 #20

    sophiecentaur

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    I'm not sure of the precise scenario that your answer comes from but, if the car is doing the same 'speed' over the surface as the station peripheral speed then its resultant peripheral speed will be twice that of the station (?). The acceleration is given by v2/r so you would expect to measure 40N, not 20N.
     
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