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Work done by man pushing a crate up a ramp, includin done on

  1. Nov 24, 2016 #1
    1. The problem statement, all variables and given/known data
    Calculate work done by an 85 kg man who pushes a crate 4.00 m up a ramp at an angle 20 degrees to horizontal.
    He exerts a force of 500N on the crate parallel to the ramp, and moves at constant speed.
    Include the work that he does on the crate and on his body to get up the ramp.

    2. Relevant equations
    I need to find the Force with which he moves himself up the ramp in other to determine the work he does on his body.
    I set up x and y components of the forces acting on the man to find the Force, and have come up with a negative magnitude.

    --Is setting the x and y components for the forces acting on the man the appropriate strategy?
    -- do I include the force of the crate on the man?


    3. The attempt at a solution
    file attached
     

    Attached Files:

  2. jcsd
  3. Nov 24, 2016 #2

    gneill

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    Staff: Mentor

    Suppose for a moment that it was only the man on the ramp (no crate). What work is required to move him 4 meters up the ramp? What force is he working against? Hint: work-energy theorem.
     
  4. Nov 24, 2016 #3
    thank you
     
  5. Nov 25, 2016 #4

    gneill

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    Staff: Mentor

    In your attached work you had this portion:
    upload_2016-11-25_6-22-46.png

    In the indicated equation what does the angle θ represent? Why did you set θ = 20° in the next line?
     
  6. Nov 25, 2016 #5
    Should angle θ be "0"
    because the force applied is parallel to the angle of the ramp?

    W =F d cos(θ) = 500 kg 4 m cos(0) = 2000 J , work done on crate
     
  7. Nov 25, 2016 #6

    gneill

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    Staff: Mentor

    Yes. The force is applied in the same direction as the motion.
     
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