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Question on Centripetal force

  • 31-03-2012 3:29pm
    #1
    bayles
    Registered Users, Registered Users 2 Posts: 258 ✭✭


    Hi Guys

    Just wondering if anybody can answer this .

    If i have a wheel approx 10" in diameter how fast would it have to be spinning in order to create centripetal force on an object inside it ? .

    I know nothing about physics im just trying to help out my son on a project . Is the weight of the object in the wheel a factor or is the size of the object in the wheel a factor or both . Is there an easy way of calculating this.

    Also would centripetal force work better if the object has a flat edge (eg) a cube rather than a ball like object which would tend to roll easier.

    Thanks


Comments

  • #2
    458
    Closed Accounts Posts: 30 ✭458


    Formula for Centripetal Force (CF) is

    CF = (m*v^2 ) / r

    where m = mass of object, v = velocity of object along the radius of curvature. and r = radius of curvature.

    If you increase the mass or velocity of your wheel, while keeping r constant you will have greater CF. Keeping m and v constant and increasing the radius of your wheel will lower the CF. If you keep m and v constant and reduce the size of your wheel, the CF will increase


  • #3
    bayles
    Registered Users, Registered Users 2 Posts: 258 ✭✭bayles


    Thanks for the reply 458

    As you are obviously well read in this subject and my degree is in business i know i am out of my depth in this area so here is my assumption , i pick up from your answer that the shorter the radius of the wheel and the larger the object inside is then the better chance of CF .

    If so then when you say "Keeping m and v constant" then what is constant ? . Would any object in the wheel not be a constant regardless of weight or size .

    Cheers


  • #4
    458
    Closed Accounts Posts: 30 ✭458


    bayles wrote: »
    Thanks for the reply 458

    As you are obviously well read in this subject and my degree is in business i know i am out of my depth in this area so here is my assumption , i pick up from your answer that the shorter the radius of the wheel and the larger the object inside is then the better chance of CF .

    If so then when you say "Keeping m and v constant" then what is constant ? . Would any object in the wheel not be a constant regardless of weight or size .

    Cheers

    I was simplifying your physical scenario (i.e. an object in a wheel (I'm not sure what you mean by this) ) to explain the idea of CF. I imagined a solid metal wheel rotating on its axis.

    As I say, your situation is more complicated. You'd have to explain it more. Are you talking about something like a bicycle wheel with an object (i.e. reflector etc) attached to the spokes?

    There would be a centripetal force on the reflector as soon as you start rotating the wheel. Varying the distance of the reflector from the center of the wheel would affect the centripetal force. Varying the mass of the reflector and the velocity of the reflector would affect the centripetal force in the same way as I described before.

    Your right about keeping the mass of the object constant. You can't change that unless you "tie something heavy onto it" or change it to a bigger object. Keeping v constant means spinning the wheel at the same speed.


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