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Homework Help: Radians Angular Displacement

  1. Feb 18, 2015 #1
    1. The problem statement, all variables and given/known data
    Coverting Cord length to radians and the other problem is: A ball Radius = 12 CM, rolls 15 M, across the gym floor. Through what angle does the ball rotate?
    We just started this today and im very confused by it. the other question is converting 11.6 CM Chord Length into Radians.

    2. Relevant equations

    3. The attempt at a solution
    I dont know how to convert chord length to radians and on the next one I converted 15M to centimeters and then i plugged it into the formula doing 1500CM/12CM which gets me 125 Radians and then I did 125(180/3.14) and got 7165 Degrees which cannot be correct.
  2. jcsd
  3. Feb 18, 2015 #2


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    Staff: Mentor

    If it makes many rotations, then angle of rotation will exceed 360°.
  4. Feb 18, 2015 #3


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    Homework Helper

    cord length, as if a cord is wrapped around the circumference?
    or chord length, as a straight line from one circumference point to another?
    (Your small ball does rotate 125 radians to roll 15 meters.)
  5. Feb 18, 2015 #4
    A cord as in straight line across it
  6. Feb 18, 2015 #5
    Cord length as in a straigt line across it
  7. Feb 18, 2015 #6


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    did you draw it? I suggest also draw 2 radial lines from the center to those circumference points . . . maybe one in the center of the chord, also.
  8. Feb 18, 2015 #7
    I did draw it and i have a problem worked out to get the cord i just cant figure out how to work back words from it I know have to cord is 5.8 CM and there is a 90 Degree angle there am i supposed to do -TAN(Y/X) ?
  9. Feb 18, 2015 #8


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    Homework Helper

    YES! we love right triangles! (don't forget the other half chord)
  10. Feb 18, 2015 #9
    alright cool thanks
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