1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Circular Motion, Revolutions from diameter, time and speed

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





    2. Relevant equations

    Relevant Equations, T=2∏r / v

    3. The attempt at a solution

    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?
    1. The problem statement, all variables and given/known data



    2. Relevant equations



    3. The attempt at a solution
     
  2. jcsd
  3. Oct 6, 2012 #2

    ehild

    User Avatar
    Homework Helper
    Gold Member

    This is the correct solution. The number of revolution was asked.

    No. But nobody asked the number of revolutions in one second.
    An other note: Do not use more significant digits in the result than the number of the significant digits in the data.

    ehild
     
  4. Oct 6, 2012 #3
    Thank you very much ehild, so 67.22 REV is correct?
     
  5. Oct 6, 2012 #4

    ehild

    User Avatar
    Homework Helper
    Gold Member

    Yes, but better to write 67 rev only.

    ehild
     
  6. Oct 6, 2012 #5
    Thank you very much! Is there a way I can rate you as excellent?
     
  7. Oct 7, 2012 #6

    ehild

    User Avatar
    Homework Helper
    Gold Member

    Thank you :smile:

    ehild
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Circular Motion, Revolutions from diameter, time and speed
  1. Circular Motion Speed (Replies: 7)

Loading...