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Homework Help: D'Alembert's principle Help

  1. Apr 1, 2008 #1
    I need a bit of help with D'Alembert's principle, I'm after the equations to find the power in a car ascending a slope with fritional resistance. The example I will give is not my assignment question as I want to work that out for myself, but an example from a textbook that just gives me the answers and not the equations, but I cannot find a way using KE and PE to get it right.

    A car of mass 800kg accelerates from rest to a speed of 50km/h in 10 seconds, while ascending an incline of 1 in 70. The rolling resistance is 150N. Assuming uniform acceleration, what is

    1 the power developed at 30 km/h and
    2 the tractive effort

    Answer to number 1 is 11.4KW, number 2 is another baffling question I’m afraid.

    I have worked out that the acceleration is 1.389m/s and the distance travelled is 13.89

    Any help gratefully received
  2. jcsd
  3. Apr 1, 2008 #2


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    Staff Emeritus
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    Welcome to PF mitch,

    Power is simply the rate at which work is done. Therefore, if one could find the work done then calculation of the power would be trivial.
    Last edited: Apr 1, 2008
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