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Circular Motion, Revolutions

  1. Oct 6, 2012 #1
    A car is moving at a speed of 20 m/s in 4 seconds and the car's tire is 38cm around which is its diameter. How many revolutions did your tires make?

    Relevant Equations, T=2∏r / v

    My attempt at a solution:

    To get the distance travelled=20 m/s (4 sec.) = 80 m

    2∏(0.19m)= 1.19 m

    80m / 1.19 m = 67.22 Rev

    67.22 rev / 4 sec. = 16.805 rev/s ?

    is this wrong?
     
  2. jcsd
  3. Oct 6, 2012 #2
    Is this the actual text of the problem or your interpretation?
    I won't assume that "38 cm around" means diameter. Diameter is rather "across" that "around".
     
  4. Oct 6, 2012 #3
    My interpretation it says 38 cm = Diameter
     
  5. Oct 6, 2012 #4
    OK, then the only thing is that the question (as you wrote it) asks how many revolutions and not how many per second.
     
  6. Oct 6, 2012 #5
    is 67.22 rev correct then?
     
  7. Oct 6, 2012 #6
    It looks OK. If this is what the problem requires.
     
  8. Oct 6, 2012 #7
    Thank you very much for your time and patience nasu =-)
     
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