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Force on a sliding person

  1. Oct 9, 2014 #1
    1. The problem statement, all variables and given/known data
    A child lying on her back experiences 55 N tension in the muscles on both sides of her neck when she raises her head to look past her toes. Later, sliding feet first down a water slide at terminal speed 5.7 m/s and riding high on the outside wall of a horizontal curve of radius 2.4 m, she raises her head again to look forward past her toes. Find the tension in the muscles on both sides of her neck while she is sliding.

    2. Relevant equations
    F = ma
    CF = (mv^2)/r

    3. The attempt at a solution
    I thought what I needed to do was to find the centripetal force and add it to the original force but I cant do that without a value for mass. I don't know what to do
     
  2. jcsd
  3. Oct 9, 2014 #2

    Orodruin

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    What is the acceleration the head is lifted against just gravity? What is the acceleration lifted against in the slide?
     
  4. Oct 9, 2014 #3
    Against the head would be 9.8 m/s^2 . the centripetal acceleration would be 13.54 m/s^2
     
  5. Oct 10, 2014 #4

    Orodruin

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    So, if a force of 55 N is required to lift against 9.8 m/s^2, what force is required to lift against 13.5 m/s^2 with the same geometry?

    I should add a caveat here, it is not clear from the problem formulation if you also need to consider gravity. "Riding high on the outside" seems to indicate not, but you never know.
     
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