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Homework Help: What's the net work done?

  1. Feb 2, 2010 #1
    1. The problem statement, all variables and given/known data

    The longest shish kebab ever made was 881.0 m long. Suppose the meat and vegetables need to be delivered in a cart from one end of this shish kebab’s skewer to the other end. A cook pulls the cart by applying a force of 40.00 N at an angle of 45.00° above the horizontal. If the force of friction acting on the cart is 28.00 N, what is the net work done on the cart and its contents during the delivery?

    2. Relevant equations

    3. The attempt at a solution

    Would i use the formula: Wnet = Fnet(d)(Cos)? If so, then what do i look for?!
  2. jcsd
  3. Feb 2, 2010 #2
    Since the force applied is constant, it is a simple equation of W=F*d. You do need to be careful that you are using the correct force. Remember that you need the force in the direction of motion.
  4. Feb 2, 2010 #3
    So how would i set up the formula?
    W = (40.0N)(...)
  5. Feb 2, 2010 #4
    It is not 40N because that is the force at 45 degrees to the direction of motion. You want the force in the direction of motion. So first you need to find whether you multiply 40 by sin or cos. Which one gives you the x component? Then multiply by the distance you need to travel.
  6. Feb 2, 2010 #5
    Okay, that helps!
    What would i do with the friction force?!
  7. Feb 2, 2010 #6


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    The problem is asking for the NET work done. That includes the work done by ALL forces. Calculate the work done by ALL forces to find the net work done.
  8. Feb 2, 2010 #7
    Sorry. I missed the part about the friction. In which case, do what PhantomJay said.
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