Recent content by Joskoplas

Like you, I read more into it than was necessary. I'm out now. So I guess I'm not 'the hell' going on about anything.

Don't read it as an accusation; I was inputting a second perspective. You may feel, as a student, that your world sucks. There's a big list of reasons why things came to be the way they are, and a Gordian knot to untie to undo the damage.

And the teachers chose to do it this way, eh? No pressure from anyone? No mandates to serve all and please everyone? No forced accommodation for everyone's long list of disabilities, long litany of excuses, or long line of helicopter parents? It's easy to throw stones at the perpetual...

Nope. It's -5517 kJ/mol ... that "per mole" part is important. Presumably if you knew how much heat was produced, you could figure how how many moles of octane -- and if you knew that, from the molecular weight, how many grams of octane.

Precisely. It wasn't meant to.

The often-quoted principle that "a good absorber is also a good emitter" is true for the Einstein coefficients for photon absorption and emission. Perfect for atomic physics. But when you consider bulk matter, not atoms, you find that even if an individual atom re-emits the light, it could...

Gamma rays are all you'd get from the non-relativistic collision of lighter particles, like electrons and positrons. Higher mass particles ... well, think if it this way. One of the guidelines in particle physics is that if it's not forbidden, it's mandatory. When a proton annihilates with an...

Diamond.

I'm struggling to answer this, because I'm having a hard time figuring out what sort of material could be used for the hypothetical engine bell. For 'pure' annihilation, the material has to be able to reflect gamma rays ... darn hard to do. So if you're going to posit some new technology that...

Calculus (books 1 and 2) by Tom M. Apostol

Then there's the uncertainty principle itself. When you translate it from position and momentum to energy and time, you get \Delta E \Delta t \ge \frac{\hbar}{2} So, if we could force the energy level to be more precisely defined, delta E would go down. But since it has to multiply...

That is one of the coolest things I've seen in a long time. Thanks to both of you!

1e looks reeaall suspicious. If I multiplied both numbers by 10^7 (for my convenience), I'd see 390.1 + 1.0 I don't have to convert it back to the proper decimal place to see there's a problem with saying 400

Then there is the unfortunate possibility that your teacher was the one with the wires crossed. It happens. Even Einstein accidentally wrote E = MC hammer before he got it right. Well, no, but you get the point.

Weather has a lot of interesting physics. When lightning strikes, for instance, there are strange upper-atmospheric phenomena . . . flashes of light that shoot up in the opposite direction, called sprites. Also, on a somewhat inexplicable front, it's been found thunderstorms can emit gamma...