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Homework Help: Friction and air resistance of a car travelling down a hill

  1. Mar 2, 2010 #1
    A car of mass 1500 kg goes down a hill with a height of 50m. when the car reaches the bottom of the hill the speed is 15 m/s. how much energy was lost due to friction and air resistance?

    hey, im having trouble with my home work T.T I have no clue how to do it if someone can help, much would be much appreciated.

    the answer is 566 KJ but i have no clue how to get it.

    thanks in advance.
     
  2. jcsd
  3. Mar 2, 2010 #2

    rock.freak667

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    Re: Help:

    At the top of the incline, how much energy does it have? (remember it is at rest here)

    At the bottom how much energy does it have? (remember, relative to the ground, the vertical distance is zero)
     
  4. Mar 2, 2010 #3

    kuruman

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    Re: Help:

    Hi lakefall and welcome to PF. Please follow the rules of our forum. Use the template for Homework Help, post the relevant equations and show what your thinking is about your question.
     
  5. Mar 2, 2010 #4
    Re: Help:

    I'm not sure if I am doing it right, but I used KE = 1/2mv^2 and KE(final) - KE(initial), I think KE(initial) is 0 because you said it is at rest so 0 m/s = V so its 0. But for the KE(final) i got 168750 which is way off haha.

    I think I'm doing it wrong. T.T

    Hi thanks ^_^ okay ill remember to use that template and cute picture.
     
  6. Mar 2, 2010 #5

    kuruman

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    Re: Help:

    Ok, so you found the kinetic energy at the bottom. Where did that kinetic energy come from?
     
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