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Homework Help: Find minimum work

  1. Mar 2, 2010 #1
    I have been trying this problem multiple times but it still says i'm wrong:

    What is the minimum work needed to push a 800 kg car 930 m up along a 9.0^\circ incline?

    i'm using the formula:
    W= Fdcos(theta)
    F= mg

    what am i doing wrong?
     
  2. jcsd
  3. Mar 2, 2010 #2

    tiny-tim

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    Welcome to PF!

    Hi cmed07! Welcome to PF! :smile:

    (have a theta: θ and a degree: º :wink:)

    First, what is the minimum possible value of F?
     
  4. Mar 2, 2010 #3

    Andrew Mason

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    There are a couple of ways to approach this. One way is to calculate the component of force (gravity) along (ie. parallel to) the [tex]9.0^\circ[/tex] inclined surface and multiply that force by the distance (930 m). The simpler way would be to determine the height increase over that 930 m and the resulting change in gravitational potential energy of the car. The work is equal to the change in gravitational potential energy.

    AM
     
  5. Mar 2, 2010 #4
    Re: Welcome to PF!

    That's all the information that was given to me... I know i'm supposed to find force by multiplying the mass and gravity...but i think the number i'm getting after i put it into the work formula is too big...
     
  6. Mar 3, 2010 #5

    tiny-tim

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    D'oh! :rolleyes:

    On the information that was given to you, what is the minimum possible value of F? :smile:
     
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