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Need help with a centripetal force question

  1. Oct 6, 2016 #1
    1. The problem statement, all variables and given/known data

    media%2F837%2F837b1205-3600-4f55-9ce0-ecab40407d1e%2FphpeyTTSA.png

    2. Relevant equations

    mv^2 / r = F

    3. The attempt at a solution
    This is my attempt and reasoning for this problem, is this the correct way to approach the problem or am i missing something?


    the hanging mass is motionless the tension in string equals the force of gravity on mass m2, therefore
    T = 4*9.8N
    The horizontal force on the puck (which is the centripetal force) is the same as the tension.
    F(horizontal) = 4*9.8 N
    (c) mv^2 / r = F(centripetal) ===> (0.8)(v^2) / (1.5) = 4*9.8 ===> v = 8.57321 m/s
     
  2. jcsd
  3. Oct 6, 2016 #2

    gneill

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    Staff: Mentor

    Your logic and method look good. You'll want to display the end result with the correct number of significant figures though.
     
  4. Oct 6, 2016 #3
    Are you sure the answer is correct? The solution key that the professor just posted said the answer was 10.5 m/s so i'm trying to figure out where i went wrong.
     
  5. Oct 6, 2016 #4

    gneill

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    Staff: Mentor

    I don't see any problem with your solution. Your result is correct for the problem given.

    You might make your answer 10 m/s if you were rounding to one significant digit, but your professor's result has three. So that won't account for the difference.
     
  6. Oct 6, 2016 #5
    ok thank you for your help
     
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