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The 1100 kg mass of a car includes four tires

  1. Dec 28, 2014 #1
    1. The problem statement, all variables and given/known data

    The 1100 kg mass of a car includes four tires, each of mass (including wheels) 35 kg and diameter 0.80 m. Assume each tire and wheel combination acts as a solid cylinder.
    If the car is initially at rest and is then pulled by a tow truck with a force of 1500 N, what is the acceleration of the car?

    2. Relevant equations

    F = ma
    T = I*alpha
    I = 1/2*m*r^2

    3. The attempt at a solution

    It is apparent that doing acc = 1500/1100 leads to a wrong result. We must consider the tires and their accelerations. But I don't know how I can combine "ma" with "I*alpha" in the same equation, to solve for "a".
     
  2. jcsd
  3. Dec 28, 2014 #2

    Bystander

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    This bit of information, and the following bit
    if put together correctly should help you.
     
  4. Dec 28, 2014 #3

    PeroK

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    Is the speed of the car not related to the rotational speed of the wheels?
     
  5. Dec 28, 2014 #4
    Yes the right hand side of that equation(T = I*alpha) is known, but I don't think the left side can be calculated simply by F*r. Is it the whole force that contributes to torque of a tire?
     
  6. Dec 28, 2014 #5

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    The angular moment of inertia resists the acceleration.
     
  7. Dec 28, 2014 #6
    Have you done a free body diagram on the car? How is the rate of rotation of the tires related to the linear speed of the car? Have you at least included the mass of the tires in the overall mass m of the car when applying F = ma.

    Chet
     
  8. Dec 28, 2014 #7
     
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