Speed of spinning wheel?

  1. How would I calculate the speed of a spinning wheel (using forces in Newton and anything else required)?
     
  2. jcsd
  3. jtbell

    Staff: Mentor

    How would you calculate the linear speed of an object moving in a straight line?

    (seriously, we need more details about where you're starting from!)
     
  4. Take a roulette wheel. How would you calculate the speed of the spinning when the roulette wheel is spinned from the middle (by hand)?
     
  5. russ_watters

    Staff: Mentor

    You need the force, the point at which the force is applied (to get the torque), the duration for which the force is applied and the moment of inertia of the wheel.
     
  6. Could you please give me an example?
    Physics in The Netherlands have a couple of different declarations, but I'll figure it out with an example of your explanation.
     
  7. rcgldr

    rcgldr 7,526
    Homework Helper

    The "speed" of a wheel is it's rate of rotation. The angular inertia depends on the distribution of mass around the center of rotation. Angular momentum is the angular rate of rotation (angular speed) times the angular inertia. If you want to know how fast the wheels perimeter is moving linearly, it's the angular speed in radians per second times the radius.
     
  8. russ_watters

    Staff: Mentor

    T=f*L
    s=a*t
    a=T*I
    So...
    s=f*L*I*t

    f=force
    L=lever arm length
    a=acceleration
    s=speed
    T=torque
    t=time
    I=moment of inertia

    If i were setting up a problem for a first year engineering student to solve, it would require those equations (it may also include the appropriate equation for moment of inertia). But if you're actually interested in a real world situation, then this is probably nowhere near specific enough to help you. But without more information about the problem you are trying to solve, there isn't much we can do. For example, I have no idea what the moment of inertia of a roulette wheel is and no way to solve for it because the geometry of the wheel is irregular.
     
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