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Homework Help: Energy problem

  1. Jan 19, 2007 #1

    lzh

    User Avatar

    1. The problem statement, all variables and given/known data
    Karen has a mass of 54 kg as she rides the
    up escalator at Woodley Park Station of the
    Washington D.C. Metro. Karen rode a dis-
    tance of 59:5 m, the longest escalator in the
    free world.
    The acceleration of gravity is 9:8 m=s2 :
    How much work did the escalator do on
    Karen if it has an inclination of 29:4±? Answer
    in units of J.


    2. Relevant equations
    W=F*x*cos(theta)
    where F= force, x is displacement and theta is the angle between the 2


    3. The attempt at a solution
    I first drew a force diagram. And used it to figure out this:
    mg=529.2N
    F=529.2*cos60.6=259.786N <-force of escalator
    Next i plugged it into the Work equation:
    the angle between the displacement and force is 0, so cos(theta)=1:
    W=259.786*59.5*1=15457.28285J

    is this right? I just need a confirmation, because I can't afford to get this wrong. Ty in advance
     
  2. jcsd
  3. Jan 19, 2007 #2
    looks good!
     
  4. Jan 19, 2007 #3
    but using 60 instead of the exact value makes your answer inaccurate
     
  5. Jan 19, 2007 #4

    lzh

    User Avatar

    60? for:
    F=529.2*cos60.6=259.786N <-force of escalator
     
  6. Jan 19, 2007 #5
    haha, sorry, I didn't see the .6
     
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