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Homework Help: A grade 12 physics dynamics problem

  1. Dec 10, 2014 #1
    1. The problem statement, all variables and given/known data
    A boy drags his 80 n sled at a constant speed up a 15 degree hill. He does so by pulling with a 35 n force on a rope attached to a sled. If the rope is inclined at 35 degrees to the horizontal, what is the coefficient of kinetic friction between snow and sled

    At the top of hill, he jumps on sled (weighing 50 kg, the boy) and slides down the hill. What is his acceleration?

    2. Relevant equations

    Fnet= ma

    Ffk = mew fn

    And so on, so forth.

    3. The attempt at a solution

    I drew a FBd, including angles, and force locations, but I do not know how to use the angles to find the required forces.

    As well, as a general question, how do you use angles in the diagram to find things?
  2. jcsd
  3. Dec 10, 2014 #2
    My main problem is that I know the Fg, which is ma (9.8)

    After that, I get slightly lost due to the angles, and am unable to find even the most basic fn.
  4. Dec 10, 2014 #3


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    Science Advisor
    Homework Helper
    Gold Member

    if you can't post the diagram, at least try to describe it. What forces operate, what magnitudes and what directions?
    Invent symbols for all values so that the algebra can be done symbolically. Only plug the numbers back in at the end.
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