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Centrifugal or what?

  1. Mar 20, 2009 #1
    centrifugal or what??

    Hello all!!

    i have been reading different books thoughout the years and some people talk generally about centrifugal force being not a real force.

    Know would someone please explain if why this is the case.

    Also how do you find the force on a wall of a spinning object say a closed square full of a cubic metre of water. Because i have read that there are different forces applying on a surface other than centrifugal.

    If somon could give me an example of this and it would be great because i don't understand this matter.

    Ps take your time - i've got heaps and in no rush.

    Thanks guys
     
  2. jcsd
  3. Mar 20, 2009 #2
    Re: centrifugal or what??

    Centrifugal force does not actually exist. Centrifugal force is a force coming out from a center point. The real force is centripetal force which means a a center seeking force. The object travels in circular motion or an orbit because of a force pulling upon it radially to a point in the center. Here is a supporting link. http://www.newton.dep.anl.gov/askasci/phy00/phy00305.htm

    Centripetal force can be calculated by newtons universal law of gravitation.

    F = [m(v^2)]\r

    F = force
    m = mass of object
    v = velocity (which is sqaured in this case)
    r = radius

    Force is equal to mass times velocity sqaured all over the radius.

    Examples for this could be a ball on a string being spun in a circle, the moon orbiting the earth or a vehicle traveling around around a circular freeway curve.

    Hope this was of some help.
     
  4. Mar 20, 2009 #3
    Re: centrifugal or what??

    I'm not really sure I agree with that explanation. Also, that's not Newtons Law of Gravitation, its just his second law. AKA F=dp/dt in a different form. This is newtons law of gravitation;

    b65000f8f887a68545ce63eb1cada232.png


    It's true that centrifugal forces don't technically exist, its just that from a simple perspective it seems like they do. Centrifugal forces are simply created by the inertia of an object wanting to keep going forward. For example, spinning a ball on the end of a string. Your are giving the ball a forward velocity component, but because of the string you are causing an constant acceleration to make the ball move in a circular path. And as newton's second law says, any mass that undergoes an acceleration or a change in momentum must have a force acting upon it. So this reactive force that you are feeling from the ball wanting to keep going forward is what we call the centrifugal force. It's not actually pulling the ball outward, its just the ball wanting to keep going strait. Perhaps someone can explain it better, I always just seem to confuse people.
     
  5. Mar 20, 2009 #4

    DaveC426913

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    Gold Member

    Re: centrifugal or what??

    This is correct. If you suddenly cut the string, the ball will not going flying outwards, it will actually continue along its present course which is tangential to the circular path. This demonstrates that there was no centrifugal force pushing the ball outward, it was just the inertia of the ball. (line AB in the diagram)

    fig5-4.jpg
     
  6. Mar 20, 2009 #5
    Re: centrifugal or what??

    Yea, i tried to keep it simple, its a hard concept to explain without the use of demonstrations and diagrams, Dave managed to find a pretty nice one however.
     
  7. Mar 20, 2009 #6
    Re: centrifugal or what??

    So yea i take back that statement. Its not worded correctly as the diagram demonstrates.
     
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