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General Discussion & Feedback => Just Chat! => Topic started by: Curious Cat on 30/09/2021 10:47:23

Title: A lot of us use "Exponentially" when it should really be "Quadratically"!
Post by: Curious Cat on 30/09/2021 10:47:23
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Title: Re: A lot us use "Exponentially" when it should really be "Quadratically"!
Post by: Bored chemist on 30/09/2021 13:36:32
Really?
When was the last time U saw quadratic/al/ly? I can't remember.
All I can remember is nonlinear and exponential/ly.
Well, there's a stack of references to the inverse square law.
Most functions aren't quadratic.
Plenty of things - notably economic and microbiological growth are roughly exponential.
So, you see exponential used a lot, because it's often the right word (and often "figuratively" the right word).
Title: Re: A lot us use "Exponentially" when it should really be "Quadratically"!
Post by: alancalverd on 30/09/2021 14:36:41
Journalists and politicians now use exponential to mean rapid, but they are not "us".
Title: Re: A lot us use "Exponentially" when it should really be "Quadratically"!
Post by: Bored chemist on 30/09/2021 17:54:26
Roughly speaking...
For any given shape, the area varies as the square of the height.
Computing power rises exponentially with time.
The cost of a given amount of computing power falls exponentially with time.
Current varies with the reciprocal. of resistance.
The typical instructions for time taken roasting meat are a linear, but not proportional function of time, but it's not proportional, because there's an offset.
20 minutes per pound  + 20 minutes.

And some are just plain silly.
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Title: Re: A lot of us use "Exponentially" when it should really be "Quadratically"!
Post by: alancalverd on 30/09/2021 23:18:30
....which brings in the concept of hyperbolic expansion.
Title: Re: A lot of us use "Exponentially" when it should really be "Quadratically"!
Post by: Bored chemist on 01/10/2021 08:56:14
I missed "factorially" off the list.
It's one of the few simple mathematical functions that rises faster than exponentially.
Among other things, it's the expression for the number of ways you can randomly assign n different letters to n addressed envelopes.
It is therefore, in some ways, the answer to "How many ways can things go wrong?".
You might have guessed that would rise quickly.
:-)

It's also interesting to see what that weird  equation I cited earlier is actually trying to model.
Here's the (measured) heat capacity of nitrogen vs temperature (K).
As you can see, to a reasonable precision, it is about 1.2

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