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Author Topic: The Truly Magical Bullet  (Read 17599 times)

Online Mitch Todd

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Re: The Truly Magical Bullet
« Reply #270 on: June 10, 2018, 07:01:08 AM »
Not sure how this advances the SBT, but welcome to physics. But don't confuse practical with hypothetical. Hypothetically speaking, anything is possible and "complicated" is a relative term.

You're a little late. My welcome to physics came in the 80's. Anyway, I used the progression out of F=ma as an example because it's well enough documented that it's hard to argue with. And it's a good example of something that is generally taken as simple and foundational  is more complicated that folks tend to think.

Offline John Mytton

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Re: The Truly Magical Bullet
« Reply #271 on: June 10, 2018, 07:02:00 AM »
So you should be able to explain what was wrong with the physics I posted with little difficulty.

And, no, it wasn't cut-n-pasted from Wikipedia or anywhere else. I'll even repost what I wrote.

Consider for a moment Newton's second law, F=ma. Simple isn't it?

But it doesn't tell the whole story. It assumes that the mass cannot deform, and that there is no drag acting on it once it moves.

So, the real equation has to add those terms, and we get the familiar 2nd order ODE, F=ma+cv+kx where cv is the the drag term and kx represents the deformation of the mass under load. F=ma is simple, but F=ma+cv+kx is correct.

At least, more correct. F=ma+cv+kx assumes that the ma, cv, and kx terms are linear. But they really aren't. It turns out that mass is a function of velocity, and kx is only considered to be linear through a relatively limited range of x-values.

Removing the assumptions makes things more complicated.

Hey Mitch watch out, Trojan our resident Einstein is on record as being a Nuclear Scientist/Photogrammetrist/Optical Printer Operator/Film Editor/Special Effects Supervisor/Physicist/Lasers lasers lasers/ etc etc etc...
So yeah, basically whatever hat needs to be worn, he's worn it!



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