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Grade 12 Physics help, Kinematics

  1. Sep 18, 2007 #1
    1. The problem statement, all variables and given/known data
    Alright, just started physics and i've already fallen behind :(

    trying to do my homeowkr and im completely lost, no idea at all.

    So heres a question which i had no idea how to do.

    * A tree house has a vertical "fire pole" of smooth metal, designed for quick exits. A child of mass 35.7Kg slides down the pole with constant acceleration, starting from rest. The pole is 3.10m high. The journey to the ground takes 2.00s.
    a) what is the magnitude of the downward acceleration of the child?
    b) What is the magnitude of the upward force of friction exerted by the pole of the child?

    Also, i looked in the back of my textbook and in my notes, and i still dont know what magnitude means. Or how to get it for that matter.

    2. Relevant equations
    I know for this problem to find a) i could use the equation a= external friction/mass
    but how do i find a? is it just g= -9.8m/s² or does it have to do with the kids weight?
    and i have no idea how to get the external friction or what exactly it is.

    I know this right now
    T= 2s
    Height= 3.1m high
    g= -9.8m/s²

    i dont know if this is enough information but please help me, its been 2 weeks and im already behind, ive gone to extra help after school, but its the same teacher and i guess i just dont understand him.
  2. jcsd
  3. Sep 18, 2007 #2


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    Homework Helper

    For the first part don't use forces... just use kinematics. You can immediately calculate acceleration by using the right equation.
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