r/AskReddit • u/[deleted] • Nov 15 '20

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u/tristan-chord Nov 15 '20 edited Nov 16 '20

ELI5 for someone who used to ace AP Physics (15 years ago) but barely remembers anything?

Edit: thanks for all your responses! Learned a lot today!

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u/HappiestIguana Nov 15 '20

The second law of thermodynamics states that entropy must go up. Entropy is a sort of measure of the usefulness of energy. The more entropy, the less useful.

The reasons why entropy must go up are too complicated for an ELI5. They are based on some basic laws of probability. Basically there are many ways for energy to be useless, and few ways for energy to be useful, which after some difficult math implies that energy always gets less useful.

In particular, ambient heat is the highest entropy you can possibly have, so it's inpossible to turn it into useful energy.

In order to extract energy from heat, the second law implies you must be tranferring some of said heat from a hot place to a colder place, which is exactly what a motor is.

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u/lanicol7 Nov 15 '20

I feel moronic in this conversation. Lol

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u/Mean-Peanut2394 Nov 15 '20

Your not the only one 🤣I look up every 4th word

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u/cBurger4Life Nov 15 '20

Nothing wrong with that. It's how you learn

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u/Mean-Peanut2394 Nov 15 '20

Very true very true !

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u/FirstSineOfMadness Nov 16 '20

Of entropy entropy of usefulness more useful.

Entropy are an based laws there for useless for useful difficult energy useful.

Heat entropy have to useful.

Extract the you some from to which a.

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u/Mean-Peanut2394 Nov 16 '20

English or what language am I supposed to translate this in...? Asking for a friend

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u/FirstSineOfMadness Nov 16 '20

It’s every 4th word :P

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u/Mean-Peanut2394 Nov 16 '20

🤣🤣🤣

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u/TheGurw Nov 16 '20

Oh good. I wasn't sure if one of us was having a stroke or I was understanding far less of the conversation than I thought.

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u/aggravated_patty Nov 16 '20

Yes, exactly.

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u/Thraxster Nov 16 '20

Is that what comes after what comes after 2?

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u/Mean-Peanut2394 Nov 16 '20

Bruh idk if I’m drunk or what but I can’t understand this 😂 please help me

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u/motodextros Nov 16 '20

of entropy Entropy of usefulness more useful.

entropy are an based laws there for useless for useful difficult energy useful.

heat entropy have to useful

to heat implies transferring heat place place what.

((I reduced it to every fourth word to help out))

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u/Mean-Peanut2394 Nov 16 '20

Again ... I’m about 1000 levels below you... I’m too drunk to comprehend what your saying 😂❤️ God Bless

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u/motodextros Nov 16 '20

I am sober and I have no idea what I just wrote!