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Homework Help: Rotational kinematics

  1. Nov 2, 2004 #1
    This problem is supposed to be easy, but I can't seem to figure it out.

    ----A bicycle with 62.8cm diameter tires travels 7.90km. How many revolutions do the wheels make? ----

    I know I can use the circumference somehow...if anyone can help me out I'd really appreciate it. :)
  2. jcsd
  3. Nov 2, 2004 #2


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    What is the distance the bicycle travels in one revolution of the wheel?
  4. Nov 2, 2004 #3
    Try finding the perimeter of the circle and then diving the total distance by it.

    Since one circle perimeter = 1 revolution
  5. Nov 2, 2004 #4
    So if I find the circumference and divide that by the total distance, I'd get how many revolutions? Because I did that...0.628mPi / 7900m = 2.49E-4...but the program says I'm wrong..hmmm....or if I multiply the two...it's still comes out wrong...yup, I'm still lost...sorry :/
  6. Nov 2, 2004 #5
    You have the total distance 7900 M and you have the distance traveled in one revolution, .628 meters.

    You're trying to find out how many revolutions go into the total distance.
  7. Nov 2, 2004 #6
    Your goal is to figure out how many revolutions the tire must make in order to travel 7900 metres. In one revolution the tired travels .628pi metres. In two revolutions it will travel 2*.628*pi revolutions, in 3, 3*.628*pi. So how many revolutions must it make to travel 7900 metres?
  8. Nov 2, 2004 #7
    you divided wrong it's supposed to be total distance divided by the 0.628mpi
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