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Question about gravitational acceleration

  1. Oct 26, 2012 #1
    not so good at math so please help me.When I play with those artificial gravity or should say centripetal force calculators I get some pretty big numbers so I need some verification of them.
    Is it true that spinning a let's say 1m. radius disc with 50 000rpm/min you would get like 2795609.8954 g force on the side of the disc? And if so isn't that close or even over to that you normally would get on a middle sized star? Certainly bigger than our sun.?


    How could I calculate the highest possible g force a specific flywheel or material or disc could withstand?

    And the last thing a disc or whatever solid material rotating fast doesn't get very hot , well if we don't consider the air resistance and friction, but now let's imagine that around the disc is a chamber full with gas and we spin the disc very fast does the gas act similar as the solid or does the gas heat up differently?
     
  2. jcsd
  3. Oct 26, 2012 #2
    F = ma..right?? and for a rotating object ....a = v2/r

    the v is the tangential velocity so you'll have to convert 50,000 RPM to a velocity. Each revolution travels a distance of 1 circumference or C = 2[pi]r....and you'll have 50,000 of these each minute....


    not likely practical to calculate it.....use an experimentally determined figure:

    see

    http://en.wikipedia.org/wiki/Tensile_strength
     
  4. Oct 26, 2012 #3

    jbriggs444

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    Science Advisor

    If you look at

    http://en.wikipedia.org/wiki/Flywheel_energy_storage

    you can get some additional insights.

    One observation is that the maximum energy density you can get is proportional to σ/ρ where σ is the tensile strength of the material and ρ is its density.

    This means the the maximum tangential velocity is proportional to the square root of σ/ρ
    And that means that the maximum rotation rate is roughly given by sqrt(σ/ρ)/r.
     
  5. Oct 26, 2012 #4
    Thanks for the answers , oh by the way can somebody answer the last part of my thread?

    And the last thing a disc or whatever solid material rotating fast doesn't get very hot , well if we don't consider the air resistance and friction, but now let's imagine that around the disc is a chamber full with gas and we spin the disc very fast does the gas act similar as the solid or does the gas heat up differently?
     
  6. Oct 26, 2012 #5
    So F=ma mass let's say 5 tons and radius of the disc 10 meters. and "a" is like (assuming 50 000rpm) C = 2[pi]r that would be like 2x(3.14x10) == 2x 31.4=62.8
    now a = v2/r that would mean a=62.8x62.8/10 is equal to 394.384

    now the F=ma part. F=5000x 394.384= 19711920 (N)

    I'm sorry for my abstract nonsense type of calculus but could someone verify that I did the calculations right?
    And 19711920 N , how do I convert that to G ?

    Thanks.
     
  7. Oct 28, 2012 #6
    Anyone? And yes could someone tell me about how does gas or plasma states react to tangential pressure compared with a solid material?
     
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