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I Speed, energy, power and air resistance

  1. Apr 2, 2018 #1
    What is wrong here. If I double speed drag will be 4 times higher. The engine needs to put out approximately 4 times more power. Energy consumption will be 4 time higher for a specific time period. However if it is a fixed distance I will arrive in half the time an the energy consumption will therefore only double. Now if I look on the formula E=FxS (energy=Force x Distance) the force will be 4 times higher and therefore also the total energy needed. //Thanks
     
    Last edited: Apr 2, 2018
  2. jcsd
  3. Apr 2, 2018 #2

    russ_watters

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    Staff: Mentor

    No, power (energy over a specific time) is 8x higher. Drag is 4x higher, and speed is 2x higher (or time is 1/2 as long).
     
  4. Apr 2, 2018 #3
    Well, then it make sense. Not very intuitive (to me) that power increase that way in relation to drag.
     
  5. May 18, 2018 #4
    the aerodynamic drag force is proportional to the square of the speed
    power required is : ( aerodynamic drag force overcome (+ rolling resistance if you want) ) * speed

    if fuel consumption is energy consumed, is this power * time ?
     
  6. May 18, 2018 #5

    russ_watters

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    Staff: Mentor

    That's correct...if you also include engine efficiency.
     
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