Speed, energy, power and air resistance

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SUMMARY

The discussion centers on the relationship between speed, power, and aerodynamic drag in vehicles. When speed is doubled, aerodynamic drag increases by a factor of four, necessitating an eightfold increase in power output to maintain that speed due to the energy consumption over time. The formula E=FxS (energy = Force x Distance) is critical in understanding that while energy consumption for a fixed distance doubles, the power required is significantly higher when factoring in drag and engine efficiency. Participants clarify that the aerodynamic drag force is proportional to the square of the speed, impacting overall energy requirements.

PREREQUISITES
  • Understanding of aerodynamic drag and its relation to speed
  • Knowledge of power, energy, and their formulas (E=FxS)
  • Familiarity with engine efficiency and its impact on fuel consumption
  • Basic concepts of rolling resistance in vehicles
NEXT STEPS
  • Research the relationship between speed and aerodynamic drag in fluid dynamics
  • Study the principles of power output in internal combustion engines
  • Explore the effects of engine efficiency on fuel consumption
  • Learn about rolling resistance and its impact on vehicle performance
USEFUL FOR

Automotive engineers, physics students, and anyone interested in understanding the dynamics of speed, power, and energy consumption in vehicles.

Patrick Pihl
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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
 
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Patrick Pihl said:
What is wrong here. If I double speed draft 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.
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).
 
russ_watters said:
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).

Well, then it make sense. Not very intuitive (to me) that power increase that way in relation to drag.
 
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 ?
 
dean barry said:
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 ?
That's correct...if you also include engine efficiency.
 

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