Does the amount of fuel needed to accelerate a vehicle increase quadratically?

In summary, the conversation discusses the confusion around the relationship between energy, fuel, and acceleration of a vehicle. It is stated that the amount of energy required to reach a given speed increases quadratically, but it is unclear if the amount of fuel required also increases quadratically or if the amount of energy taken from the fuel increases over time. The conversation also mentions the difference between impulse and energy and how it relates to the workings of a car. It is noted that it takes more pedal pressure or time to accelerate from 50 to 60 compared to 10 to 20. It is also mentioned that a typical gas engine is most efficient at a certain load and rpm, and that a typical car gets its best mileage at around 45mph
  • #1
Alkatran
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I've been confusing myself over how much energy it takes to accelerate a vehicle (assuming no friction/air) with a given amount of fuel.

I know that the amount of energy required to reach a given speed increases quadratically, but does the amount of fuel required also increase quadratically? Or does the amount of energy taken from the fuel increase over time?

I'm pretty sure this is me confusing impulse with energy, but I don't know the relevant details of how a car works to begin with. For example, you press the gas the same amount and for the same amount of time to go from 10 to 20 as you would to go from 50 to 60 (so same impulse). Does it use the same amount of fuel?
 
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  • #2
Alkatran said:
For example, would you press the gas the same amount and for the same amount of time to go from 10 to 20 as you would to go from 50 to 60 (so same impulse).
No, it would take more pedal pressure or more time to accelerate from 50 to 60 than it would from 10 to 20. Ignoring aerodynamic drag factor, power = force times speed, for example, horsepower = force (lbs) times speed (mph) divided by 375 (conversion factor). So even if the force is the same, the speed at 50 is five times as much as it is at 10, so it takes 5 times the power to generate the same force at 50 as it does at 10.

On the other hand, a typical gas engine is most efficient at a certain load and rpm. A typical medium or larger sized car gets it's best milage at around 45mph, a combination of gearing, rpm, and engine load.
 
  • #3
What about in a frame moving at 50 watching the car go from 50 to 60 (maybe we should use a rocket, since then the wheels won't give away the speed)?
 

FAQ: Does the amount of fuel needed to accelerate a vehicle increase quadratically?

What is energy available in fuel?

The energy available in fuel is the amount of usable energy that can be extracted from a specific type of fuel through a chemical reaction, typically combustion.

How is energy available in fuel measured?

The energy available in fuel is measured in units of energy, such as joules or calories. It can also be measured in terms of the amount of work that can be done by the fuel, such as kilowatt-hours.

What factors affect the energy available in fuel?

The energy available in fuel is affected by several factors, including the type of fuel, its chemical composition, the amount of fuel, and the efficiency of the combustion process.

What is the relationship between energy available in fuel and energy efficiency?

The energy available in fuel and energy efficiency are directly related. A higher energy available in fuel means that more energy can be extracted from the fuel, resulting in a more efficient use of the fuel.

How is energy available in fuel used in everyday life?

The energy available in fuel is used in a variety of ways in everyday life, such as powering vehicles, heating homes and buildings, and generating electricity. It is also used in manufacturing processes and in the production of goods and services.

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