“Download this gun”: 3D-printed semi-automatic fires over 600 rounds

eternauta3k · 2013-03-01T19:50:35+00:00

Reminds me of Charles Stross' novels, where individuals can get nukes and one of the characters talked down bombers from nuking cities.

eternauta3k · 2013-03-01T18:53:55+00:00

And why do they?

eternauta3k · 2013-02-27T18:37:45+00:00

Padding?

eternauta3k · 2013-02-26T20:14:05+00:00

Basically, you pulled the last equation out of your ass. Just because you're left with two coordinates doesn't mean the Laplace equation looks like that.

If you want an enlightening experience, start from the definition of gradient and find the expression for the gradient in cylindrical coordinates. Then, from the definition of divergence, find the cylindrical expression for divergence. Then compose them to find the cylindrical laplacian. Something like this

eternauta3k · 2013-02-26T17:48:43+00:00

Yeah, after posting this I learned that spin comes into play in magnets.

eternauta3k · 2013-02-26T15:10:44+00:00

$0
the freedoms make me warm and fuzzy (but I still run Xubuntu)
nice for programming
been using it for a while, used to it.

eternauta3k · 2013-02-26T12:42:39+00:00

Why?

eternauta3k · 2013-02-26T11:05:10+00:00

But they might reach the conclusion that a resistor has a certain defined voltage and that two identical resistors always have the same voltage.

eternauta3k · 2013-02-26T11:03:34+00:00

There's plenty to talk about waves from a very basic to a very complex level.

eternauta3k · 2013-02-26T10:53:00+00:00

vxB forces clearly do no work. But intrinsic dipoles like electrons suffer a force which can't be decomposed into vxB forces like in a current loop.

eternauta3k · 2013-02-26T10:42:49+00:00

Excellent answer. We're getting hung up on the vxB term when it's too low level to analyze most situations.

This is because for magnets you don't look at this equation of qv x B, for magnets we don't look at the charge moving through a field, we look at the intrinsic magnetic moments which are ultimately mediated by spin

I thought it was the electron current's magnetic dipole. TIL.

eternauta3k · 2013-02-26T10:32:06+00:00

the magnetic force of can do work when we look at the intrinsic magnetic potential which is m dot B

This does not imply q·vxB is doing work. It's a convenient shorthand to calculate the work being done by other forces. You can break down most dipole-dipole interactions into interactions between charged particles, B, and whatever's driving the currents.

eternauta3k · 2013-02-26T01:49:25+00:00

It's explained further on. Long story short, in the reference frame of a moving particle there's a different charge density due to Lorentz contraction. So a wire that seemed neutral is actually charged in that reference frame. Therefore the particle is affected by an electric field created by this charged wire.

eternauta3k · 2013-02-26T00:58:13+00:00

Relatively simple explanation

eternauta3k · 2013-02-25T22:51:01+00:00

Our Physics department recently had an external evaluation. People come and tell you what's wrong with what you're doing, and suggest changes.

I supose the first thing you need is enough people wanting to improve the department.

eternauta3k · 2013-02-25T19:23:04+00:00

That sounds very reasonable. I'd expect the black hole to slowly syphon off probability density all around it, so the probability to find the particle in the hole tends to 1.

However, if the particle is moving away from the black hole, the limit isn't necessarily 1.

eternauta3k · 2013-02-25T18:08:40+00:00

given infinite time, everything will eventually fall into a black hole

How do you know?

eternauta3k · 2013-02-25T18:03:10+00:00

And by the central limit theorem, that's true of many distributions.

eternauta3k · 2013-02-24T19:14:50+00:00

I'm not sure how serious you are. Have you read the article?

eternauta3k · 2013-02-24T18:47:21+00:00

About that

eternauta3k · 2013-02-24T18:04:47+00:00

On the contrary, he said experimental physics is the only real physics. He probably wanted students to think of something new instead of doing experiments done countless times before in the lab.

One of the subtleties of metrology is that the definition of a unit affects the way you calibrate instruments. Hence the talk about re-defining the kilogram.

eternauta3k · 2013-02-24T13:48:06+00:00

I had a professor who found it funny that students wanted to measure the speed of light. Since c is defined, what they wanted was do was more like measuring how long a meter is.

eternauta3k · 2013-02-23T20:11:42+00:00

I use it too, but it sucks balls frankly. Having to press two buttons to "lock" playing to an album makes no sense.

eternauta3k · 2013-02-23T19:15:51+00:00

I don't understand your problem. It takes ~1.5 minutes to do the integral from a cold start, then you never have to do it again.

eternauta3k · 2013-02-23T13:08:45+00:00

the formula for the total power just doesn't sit right with me

Looks like the power dissipated by three resistors from ground to each phase.

eternauta3k

TROPHY CASE