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Relationship between velocity of wheel and car

  1. Oct 5, 2012 #1
    So I've designed a car which is powered by a falling mass.
    Using Energy Questions, i.e. mgh = 0.5*I*w2
    I've worked out the angular velocity of the wheel; so my question is whether this represents this velocity of the whole car or do I need to multiply this value by 4?
  2. jcsd
  3. Oct 6, 2012 #2


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    hi dan38! :smile:

    (try using the X2 button just above the Reply box :wink:)
    your RHS needs to be the total energy of the car, ie 4 times the rotational kinetic energy of each wheel, plus the ordinary translational kinetic energy of the car-plus-wheels :wink:
  4. Oct 6, 2012 #3
    ohh i see, so basically we have mass attached to a string connected to a rotating skewer with two wheels on either side.
    so my workings would be:
    mgh = 0.5*m*v2 + 4*0.5*I*w2

    Where v = Speed of Car and m = Mass of Car
    w = Rotational Speed of Wheels

    And by figuring out the speed of the string, I can use the relationship v = w*r to find "w" of the wheel?
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