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Homework Help: Centrifuge on Mercury

  1. Sep 3, 2007 #1
    1. The problem statement, all variables and given/known data
    A laboratory centrifuge on earth makes n rpm (rev/min) and produces an acceleration of 5.90 g at its outer end.

    a. What is the acceleration (in g's) at a point halfway out to the end

    b. The centrifuge is now used in a space capsule on the planet mercury, where gmercury is .37g what it is on earth, How many rpm (in terms of n) should it make to produce 7 gmercury at its outer end.

    2. Relevant equations
    I have no clue, except for the fact that I know I will need to convert the rev/min to maybe rad/s for calculations. But besides that, I have no clue.

    3. The attempt at a solution

    I don't know at all. I don't even know where to begin. So, please if you can, Help me out. Thanks.
  2. jcsd
  3. Sep 4, 2007 #2
    So, what is the equation for centripetal acceleration? If you know that at one radius, the end radius, the acc is 5.9g then what happens when to divide the radius by two?
  4. Sep 4, 2007 #3


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    Surely the centripedal accelaration only depends on the rotation rate and not an actual 'g' - 'g' is only being used as a unit of accelaration.
    So isn't the Mercury bit is either stupid or a trick question?
  5. Sep 4, 2007 #4


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    Yes, but I think the question is asking what a person inside the centrifuge would feel as his/her weight... I think the normal force that someone inside the centrifuge would feel is what the question asks for...

    For example in an elevator accelerating downwards at g/2... The person inside would feel like his weight is mg/2 because that's the normal force acting on him.
  6. Sep 4, 2007 #5
    thanks for the help, I asked the TA and he helped out. Thanks again for all your help because it will be used on Thursday, since I have my first exam. Wish me good luck, I need it. :)
  7. Sep 4, 2007 #6


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    Exams in september? Gee, that sucks. Good luck!
  8. Sep 18, 2009 #7
    So if the radius is half, and the equation for centripedal acceleration a = V^2/R, then the acceleration at the halfway point is double? Am I correct there with the equation and all?

    And I am also struggling with the mercury question. How would one go about to find the rpm in terms of n? I just really don't know how to approach this problem. Any help would be great, thanks
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