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Work done by a car engine up a slope

  1. Aug 8, 2013 #1
    I've searched the internet hard but couldn't find anything about this so i decided to ask this to physicsforums.
    If a car is up a slope with friction and it's stopping(balanced) by using the gas pedal, what is the energy consumed by the motor of the car? I know F.x is 0 in this situation but if i'm using the gas pedal, energy must be consumed right?
    I'm starving for the answer, thank you for your interests!
  2. jcsd
  3. Aug 8, 2013 #2


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    Science Advisor

    Yes, mechanical energy is being produced by the motor and yes, that mechanical energy is not doing any work on the road.

    In an automatic transmission there is a fluid coupling between the motor and the rest of the drive train. The energy that is produced by the motor is doing work on that fluid. But the fluid is not doing any work on the rest of the drive train (the output drive shaft is stationary).

    So you have a net input of work into the transmission fluid. One can conclude the energy is being dissipated within the transmission fluid due to viscosity, heating that fluid up.
  4. Aug 8, 2013 #3

    Or if you have a manual transmission like I do then your engine is doing work on the clutch plate... I deliver pizza in a hilly place. Sometimes I stop on a steep hill, then I have to rev it like mad to just get my car to move. I can smell the clutch plate from the work that has been done on it... lol, not good.
  5. Aug 8, 2013 #4


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    Have you considered using the handbrake to aid the hill start? If you're heating up the clutch to the point that you can smell it burning, that really isn't great for it...
  6. Aug 8, 2013 #5
    Rev the engine and release the clutch with the hand brake on?

    I use the hand brake when I stop of course, but when I release it my engine has to do work on the clutch plate. I don't hold it on the hill with the clutch if that is what you are asking. At least, not any longer than I have too! A second or less probably.
    Last edited: Aug 8, 2013
  7. Aug 8, 2013 #6
    Thank you very much for your answers im glad to hear them!
  8. Aug 8, 2013 #7


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    Staff: Mentor

    ....and I think it goes without saying that it is pretty much impossible to calculate how much power you need to use to hold the hill.
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