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Cars and Thrust

  1. Oct 29, 2008 #1
    Can thrust be used to describe the force used to accelerate a typical car (piston engine)?
     
  2. jcsd
  3. Oct 29, 2008 #2

    rcgldr

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    Yes, the engine torque is multiplied by the overall gear ratio (transmission and rear end) and after losses in the drive train are accounted for, ends up as torque applied to the driven tires. The "thrust" equals the driven tire torque divided by the driven tire radius.
     
  4. Oct 29, 2008 #3

    Danger

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    It's a bit different if Howbabbyform (where the hell did that name come from? :confused:) is trying to equate hp to the thrust as measured from a jet or rocket. That ratio changes with speed and atmospheric pressure.
     
  5. Oct 30, 2008 #4
    parody of a yahoo answers question. http://www.somethingawful.com/flash/shmorky/babby.swf

    The reason why I ask the question is because on a separate forum I was saying that you can find thrust of a car with engine torque, gear ratios and tire radius (not including parasitic drag of the drive train). Someone told me that thrust wasn't the correct term to use and when I searched for better descriptions of thrust, all I could find had to do with aviation.
     
  6. Oct 30, 2008 #5

    rcgldr

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    The wiki definition wouldn't appear to the force generated by the tires, because it defines thrust as the reaction force to acceleration of some mass (such as acceleration of air by a propeller, or acceleration of spent fuel by a rocket engine).

    http://en.wikipedia.org/wiki/Thrust

    However the force applied by the tires to the earth results in a very tiny amount of linear and angular acceleration of the earth, which "reacts" with a forwards force on the tires, so could this be called "thrust"?

    I misunderstood your original question, thinking it was about the math and not about the terminology. Thrust is normally used to refer to reaction force from the acceleration gases and fluids, but the wiki definition doesn't include this restriction.
     
  7. Oct 30, 2008 #6

    Danger

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    :rofl:
     
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