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Dynamics Wagon Problem

  1. Mar 28, 2016 #1
    1. The problem statement, all variables and given/known data
    A child is pulling a wagon of mass 7.38 kg up a hill inclined at an angle of 14.3 degrees to the horizontal. The child applies a force parallel to the hill. The acceleration of the wagon is 6.45 cm/s^2 up the hill. Friction is negligible. Determine the magnitude of (a) the force applied by the child, and (b) the normal force on the wagon.

    FBD Diagram I drew:
    hShKWw8.jpg

    Correct Answers on book:
    (a) 18.3 N
    (b) 70.1 N

    2. Relevant equations
    Fnet = ma

    (a) Fnet = -Fgx + Fa
    (b) Fn = -Fgy

    3. The attempt at a solution
    (a)
    Fnet = (-Fgx) + Fa
    ma = m(-g)(cos14.3) + Fa
    (7.38)(0.0645) = (7.38)(-9.8)(cos14.3) + Fa
    71.9 N = Fa

    (b)
    Fn = Fgy
    Fn = (7.38)(-9.8)(cos14.3)
    Fn = 11.7 N


     
  2. jcsd
  3. Mar 28, 2016 #2

    TSny

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    Homework Helper
    Gold Member

    Welcome to PF!

    Note that you've used the cosine function for getting both Fgx and Fgy.

    Make sure your calculator is in "degree mode".
     
  4. Mar 28, 2016 #3
    I literally just checked it now, its was on radians. I redid the calculations and they are correct.
    Thank you so much.
     
  5. Mar 28, 2016 #4

    TSny

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    Homework Helper
    Gold Member

    Good work!
     
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