# Various ways of doing work to minimize entropy increase

• IvanAndreevich
In summary, the conversation discusses different methods of slowing down a vehicle and their potential impact on increasing entropy. The question is deemed unanswerable due to the number of unknowns and dissipation involved. However, one suggested method, regenerative braking, is considered more efficient in terms of converting kinetic energy into usable energy and therefore reducing entropy in the long run.
IvanAndreevich
[Moderator's note: Recategorized thread to "Basic".]

While driving alone through the beautiful scenery of Banff and Yoho national parks, a question formed in my mind.

Which of these modes of slowing down a vehicle by an equal amount is likely to minimize the resulting overall increase in entropy? I’m assuming that the reduction in kinetic energy can be accomplished in a less or more efficient manner.

1) Applying the brakes.
2) Opening all the windows.
3) Turning on the AC compressor, and letting the turning of the wheels power it.
4) Downshifting into a lower gear, and using engine braking.
5) Applying a rainfall.
6) Applying a magnetic field.

Any other methods that can be suggested are welcome, if they make any difference to the outcome.

A number of reasonable assumptions would need to be made about the specifics involved, and that’s fine. I realize that there may be too many unknowns and not enough specifics, or that the answer may very well be ‘same’ for all the modes involved.

I get a sense that this is either a really easy problem, or a really hard one.

Last edited by a moderator:
I don't think this question is answerable as you ask it; there are too many unknowns, and all of the methods you suggest involve a lot of dissipation and hence will probably involve a large and not easily estimated increase in entropy.

A more interesting comparison would be between any of the methods you suggest--but #1 is probably the best since it's at least the usual method for a conventional vehicle--and the following:

7) Use regenerative braking to convert the vehicle's kinetic energy to stored energy in some storage device (the usual one in a hybrid vehicle is a battery).

Technically, that would be a cooler version of #6, right?

That should obviously be better in the long run, since some of what would become entropy is stored as usable energy, right? Since it actually improves fuel economy, whereas all of the above should have the same effect.

IvanAndreevich said:
Technically, that would be a cooler version of #6, right?

No. Applying a magnetic field to the car as a whole is not at all the same as regenerative braking. As far as the car as a whole is concerned, regenerative braking is just braking; it applies mechanical force at the wheels to slow the car down. The only way magnetic fields come into it is the magnetic fields inside the motor/generator that is recapturing the energy and putting it into the battery.

IvanAndreevich said:
That should obviously be better in the long run, since some of what would become entropy is stored as usable energy, right?

Basically, yes, although the way you've put this is not quite right. The correct way to put it would be that some of what would become unusable energy is stored as usable energy. Energy does not "become entropy". Entropy increases when the amount of unusable energy increases and the amount of usable energy decreases, but energy and entropy are still distinct things.

## What is entropy?

Entropy is a thermodynamic concept that measures the amount of disorder or randomness in a system. It is also known as the measure of the unavailability of a system's energy to do work.

## What causes an increase in entropy?

Entropy increases when energy is transferred or transformed from one form to another. This can happen through various processes such as heat transfer, chemical reactions, and physical movements.

## How can work be done to minimize entropy increase?

There are several ways to minimize entropy increase, including using efficient processes and technologies, reducing waste and energy loss, and implementing proper insulation and insulation techniques.

## What are some examples of work to minimize entropy increase?

Examples of work to minimize entropy increase include using renewable energy sources, implementing recycling and waste reduction practices, and using advanced technologies to increase energy efficiency.

## Why is it important to minimize entropy increase?

Minimizing entropy increase is crucial for maintaining the sustainability and stability of our environment and resources. It also helps to increase efficiency and reduce costs in various industries and processes.

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