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Two Homework Problems!

  1. Oct 7, 2007 #1
    FIRST PROBLEM
    1. The problem statement, all variables and given/known data
    A skier of mass 70 kg is pulled up a slope by a motor-driven cable. (a) How much work is required to pull him 60m up a 30 degree slope (assumed frictionless) at a constant speed of 2.0 m/s? (b) What power must a motor have to perform this task?


    2. Relevant equations
    I am not sure what they should be.



    3. The attempt at a solution
    I do not know where to begin and with what equations.


    SECOND PROBLEM!
    1. The problem statement, all variables and given/known data
    A 50.0-kg student climbs a 5.00-m-long rope and stops at the top. (a) What must her average speed be in order to match the power output of a 200 W light bulb? (b) How much work does she do?


    2. Relevant equations
    I do not know where to begin.


    3. The attempt at a solution
    I do not have an attempt.


    Thanks for your time and help.
     
  2. jcsd
  3. Oct 7, 2007 #2

    Kurdt

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    What have you been doing in class before you got these questions? Surely you have been given some formula by the teacher. I would start by reviewing work, energy and power in whatever resources you have (i.e. text books, classs notes etc).
     
  4. Oct 7, 2007 #3
    The only equation we have been given is W= |F||d|costheta

    and I am not sure how to plug the information into the equation. I missed class the day that we did example problems.
     
  5. Oct 7, 2007 #4

    Kurdt

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    What is the component of the skiers weight parallel to the slope (simple trigonometry)? Once you have worked out that force you can multiply it by the distance travelled to find out the work.
     
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