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Physics Problem need help

  1. Sep 22, 2011 #1
    Need Help Now

    A string wound on the rim of a wheel 20 cm in diameter is pulled out at a rate of 75 cm/s. Through how many revolutions will the wheel have turned by the time that 9.0m of string has been unwound? Also how long did it take?

    I really need help with this. If you post, please show all work so I can learn how to do this type of problem.
     
  2. jcsd
  3. Sep 22, 2011 #2

    gneill

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    Staff: Mentor

    Re: Need Help Now

    joecocobo, welcome to PF.

    You'll have to follow the posting template and show your attempt at working on the problem before help/hints/guidance can be offered.
     
  4. Sep 22, 2011 #3
    1. The problem statement, all variables and given/known data
    A string wound on the rim of a wheel 20 cm in diameter is pulled out at a rate of 75 cm/s. Through how many revolutions will the wheel have turned by the time that 9.0m of string has been unwound? Also how long did it take?


    2. Relevant equations
    I don't know any equations to use


    3. The attempt at a solution
    I honestly don't know where to start, to even make an attempt
     
    Last edited by a moderator: Sep 22, 2011
  5. Sep 22, 2011 #4

    DaveC426913

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    Gold Member

    You may be overthinking it. For starters, separate the question into its two components. They are not related.


    1] A 9.0m string is wound on the rim of a wheel 20 cm in diameter. How many times is the string wrapped around the wheel?
    Do you know the relationship between the diameter of a circle and its circumference?

    2] How long will a point on the string take, moving at 75cm/s, to travel 9.0m?
    Do you know how to calculate time, given a distance and a velocity?
     
    Last edited: Sep 22, 2011
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