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Car accelerator

  1. Aug 21, 2008 #1
    Why the more you push the gas pedal , the stronger the car is (say, when pulling something)?
     
  2. jcsd
  3. Aug 21, 2008 #2

    russ_watters

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    More gas pedal = more gas!
     
  4. Aug 21, 2008 #3
    I don't think this really belongs in classical physics.. more like engineering.
    To fully understand this you'll have to know how an engine works, which would be a very long lesson.

    But in short, when you step on the gas pedal, you inject gas into a cylinder with a piston fitted inside it. The spark plug ignites the mixture of gas and air and makes it go BOOM, pushing the piston down with a lot of force. The piston is connected to the crankshaft, which converts the linear (Straight line) motion of the piston into rotational motion to spin the wheels.

    The more you step on the pedal, the more gas you inject into the cylinder. The more fuel there is, the larger the combustion and force of pushing the piston. That means the crankshaft will translate the higher force into greater torque, so the car is 'stronger'.

    There is alot more physics involved, but i hope that helps.
     
  5. Aug 21, 2008 #4
    It's easy to say : more gas => more energy => more force.
    There's a point the gas mix is optimum, above that, gas burns less effectively, but the force does get stronger when you continue to push down the pedal?
     
  6. Aug 21, 2008 #5

    russ_watters

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    The combustion process is very precisely computer controlled - they inject more air with the more gas to keep the mixture right, so the only thing that really changes is the force on the piston.
     
  7. Aug 21, 2008 #6
    So, you may not have seen some old cars/motorbikes which split out pile of black smoke when you accelarate. Even though, the force is increased.
     
  8. Aug 22, 2008 #7

    rcgldr

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    A closed thottlle restricts air flow into an engines intake manifold. When you press on the throttle, the amount of restriction to the air intake is reduced, allowing more air to flow into the engine's intake manifold. Carburetors or a fuel injection system keep the fuel air mixture ratio optimized.
     
  9. Aug 22, 2008 #8

    FredGarvin

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    That black smoke is usually oil getting burned in the process.
     
  10. Aug 22, 2008 #9
    yes right, there is a point of optimum air fuel ratio. but throttling does not mean you are increasing the fuel & air amount is kept constant. carburetor does that, fuel injection does it more effectively. Throttle => more gas(but air fuel ratio remains constant).
     
  11. Aug 23, 2008 #10
    NO gasoline burns black when rich [unburnt carbon smoke ]
    as does diesel
    oil burning smoke is gray
    coollent is white [steam]
     
  12. Aug 23, 2008 #11

    FredGarvin

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    I had a '79 Camaro that begged to differ on that. I had a serious leak that allowed oil to get into the combustion side of the cylinders. The smoke cloud was VERY black.
     
  13. Aug 23, 2008 #12
  14. Aug 24, 2008 #13

    brewnog

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    Fred, we typically class oil smoke as being blue/grey, although if it's very thick it can certainly look black (just because it's blocking so much light!). However, if you compare it to the black smoke emitted during partial combustion, you'd definitely call it blue/grey rather than black. Unburnt fuel is white.

    I've had occasions where trucks going past work have had to put their fog lights on before, due to the amount of black and white smoke produced while I've been testing fuel systems...
     
  15. Aug 24, 2008 #14

    FredGarvin

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    Well, it was a while ago. It looked pretty darned black to me, but it could have been a dark blue. It definitely was not white.
     
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