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Homework Help: Finding the power and work needed

  1. Mar 7, 2010 #1
    This is the orginal problem.....a.)How much power is needed to push a 95 kg chest at 0.62 m/s along a horizontal floor where the coefficient of friction is 0.78.(ans. 450W)... b.) How much work is done in pushing the chest 11 m? (ans. 7.99x10^3 J)

    New question: Answer the previous question when the floor slopes upward at an angle of 5 degrees, and you push parallel to the floor.



    Fa=(coefficient of friction)(mg)
    P=(F) (v)
    W=(F) (delta x)



    My attempt is W=(95kg)(9.81m/s^2)(11m)(sin5 +cos5(.78))= 8.81 x10^3 J so solving for power I would use Work/17.74= 496 Watts
    .
    A different route is P=(.78)(95kg)(9.8m/s^2)(cos5)(.62)=448 W
    (solving for t I get 11m/.62m/s=17.74 s) so W=448x17.74 which is 7.96 x10^3 J
    -both of these answers are smaller so I do not believe this is true
    I am unsure if either of these is right and if both are wrong where have I gone wrong! thank you
     
  2. jcsd
  3. Mar 8, 2010 #2

    PhanthomJay

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    this looks good
    what happened to the sin5 piece... ?? The push force and power required must overcome both friction and gravity.
     
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