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Homework Help: Force Of Gravity

  1. Mar 15, 2005 #1
    I need help in calulcating the velocity that it is neccesary to spin a 200 m circle in order to make the force some one would have against the floor of this circle be the same as on Earth.

    No given mass. only the force neccesary and the radius.
    Last edited: Mar 15, 2005
  2. jcsd
  3. Mar 15, 2005 #2


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    is the circle spinning horizontally or verticaly?

    if horizonatally, then you could use the forumula, a= (v^/r), where a is the centripital acceleration, v is the speed of the spinning circle, and r is the radium. then you just set a = to 9.81 m/s^2 and solve for v.
    but the fact that you said the "floor" of the circle, leads me to believe that it isnt spinning horizonatally.

    if it is spinning vertically, then again you could use the same formula, but the question is, at what position is the mass being spun? (at the very bottom/top, at one side), the force the object experiences will varry from location to location if the circle is given a constant speed.
  4. Mar 15, 2005 #3


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    Dont forget to square the velocity

  5. Mar 15, 2005 #4


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    oh yes, typo, I didnt type the 2.

    also, another note on if it is rotating vertically,
    if the object is at its lowest postion, the force it feels is equal to the centripital force + its weight, and a the top it is equal to the centripital force - its weight. at the far right and far left (perfectly horizontal to the rotationaly axis) it only feels its weight.
  6. Mar 15, 2005 #5
    thank you for the quick reply. I forgot to mention that the circle is in space so it doesn't matter its orientation. Using the a = v^2/r I got an answer of 44.29 m/s. Thank you for your replies.
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