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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:

    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
    Fnet = (-Fgx) + Fa
    ma = m(-g)(cos14.3) + Fa
    (7.38)(0.0645) = (7.38)(-9.8)(cos14.3) + Fa
    71.9 N = Fa

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

  2. jcsd
  3. Mar 28, 2016 #2


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    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


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    Good work!
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