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Rotating Platform Question

  1. Apr 9, 2008 #1
    Hi, nice to find a physics forum. I had a quick question.

    I'm a television producer and developer, primarily in the unscripted TV area. We're developing a quiz show which utilizes a center circular platform. It's divided into thirds, with a different person standing on their own third. Across from them, not on the platform and stable on the actual stage, is a monitor.

    The catch for our show is that if you miss a question, you move jobs and positions. So, for instance, the person in position one moves to position two, position two to three, and position three to one. The most visually entertaining way we figured to do this is have the center circular platform rotate. Sort of a sit and spin, if you will, though the players will be standing up and holding onto padded railings.

    We're trying to make sure we can safely rotate the players only 120 degrees each time to their new position in a speed which takes around five seconds to get to. It'll be starting at a stand still and stopping when the platform rotates 120 degrees to the next position.

    My question to you physics experts is how fast would we have to rotate a platform that's roughly eight feet in diameter to move 120 degrees in five seconds, give or take a second. We're not looking for anything high speed. It's more of a time penalty and a visual aid for viewers than anything. My second question then is, with padded railings and grips so you can hold on tightly, would this be safe at all to do, given the speed?

    If you need any more information, I'd be glad to supply it. Thanks!
  2. jcsd
  3. Apr 9, 2008 #2

    Shooting Star

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    The linear speed at the circumference would be around 1.67 ft/s. But that is not very important. The centrifugal acceleration acting radially outward, which is the thing to look out for, would be around 0.175 ft/s^2, which translates to 0.022 g, which is around 1/50 of the gravity at the surface of earth. This is assuming that the angular speed is constant.

    In reality, the angular speed would not be constant, and the platform would have to speed up and then slow down. Let's assume that it speeds up with uniform angular acceleration up to 60 deg, and then slows down for the next 60 deg. In that case, the maximum centrifugal acceleration at the the halfway mark would be double the former value, i.e., (1/25)g.

    These values of g forces seem to be completely safe. Of course, you would be conducting trials. I doubt that you'll need those railings and grips.
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