swansont

"I do not feel obliged to believe that the same God who has endowed us with sense, reason, and intellect has intended us to forego their use." -- Galileo Galilei

Energy is a property that things have. "We can have a metre of string or a kilo of jam or the energy of mass" is ill-formed, but that doesn't become "We can have a metre of string or a kilo of jam or a joule of energy" because you have to go further and describe what has the energy as that's what you've done before. You didn't say "We can have a metre of length or a kilo of mass" whioch would be the equivalent formation of the statement "a joule of energy." You might also have to describe what type of energy, as we make distinctions between them. (which you would have to do if it turned out that gravitational and inertial mass were different) So, is this anything but semantic games?

Along its length. If you plucked the strings you'd get some sound in the cans. Normally the ends of a string in guitar are fixed, so you get a standing wave in the string (and there's a whole bunch of physics in the different ways you can get sound: strummed, plucked, struck, etc. — you get different waveforms) with the bridge vibrating perpendicular (more or less) to the sound board. With the speaking into the can, then end of the can acts like a diaphragm, and sends the compression wave along the string, which is picked up by the other can. If you were to pluck the string between the cans, the ends wouldn't be strictly fixed, which should change the sound somewhat, and you might get an interesting effect, because the resonance of the cans would give you a sound that could be different than the normal sound of a similar guitar string.

FYI, from http://en.wikipedia.org/wiki/Sodium_acetate Sodium acetate is also used in consumer heating pads or hand warmers and is also used in "hot ice". When sodium acetate trihydrate crystals (melting point 58 °C) are heated to around 100 °C, they melt. When this melt cools, it gives a supersaturated solution of sodium acetate in water. This solution is capable of supercooling to room temperature, well below its melting point, without forming crystals. By clicking on a metal disc in the heating pad, a nucleation center is formed which causes the solution to crystallize into solid sodium acetate trihydrate again. The bond-forming process of crystallization is exothermic, hence heat is emitted.[1] [2][3] The latent heat of fusion is about 264-289 kJ/kg.[4] Which confirms what yourdad said, that you have to supersaturate the solution (though the wiki note that in order to melt them you have to heat them to 100 ºC even though the melting point is 58 ºC is contradictory)

An electron has momentum because of its mass and its velocity. A photon has momentum because it has energy.

"Alas, to wear the mantle of Galileo it is not enough that you be persecuted by an unkind establishment, you must also be right." Robert Park

Ah, that's actually somewhat different. Sound with the tin cans is passing through the string (i.e. longitudinally) and couples to the tin can at the far end, while with the guitar it is a transverse oscillation that couples to the air. But if you play like Clapton or Knopfler, it is magic.

The momentum will be conserved if there are no net external forces (which is usually assumed when analyzing collisions). If one wants an easy example to demonstrate that speed is not conserved, consider a completely inelastic collision. With the target at rest, the final speed is always less than the incoming particle's speed.

That was the big question 100+ years ago. It turns out that electric and magnetic fields do not rquire a medium, and that they can induce each other when they change in time. The result is an electromagnetic wave, which requires no medium.

It's insulting, but then, I enjoyed it. Yourdad has already addressed the first point, and most of the other two points. I would add that you can have radiative heat transfer (which is always at the same speed) and a system with constant static pressure that is free of sound as counterexamples which falsify your claims.

It's just that the third law is so often misunderstood in precisely that way. I didn't want to reinforce the misunderstanding.

The question is ill-formed. kilo and meter are units of measurement, but mass is not. You have quantified a length and a mass, but not the energy.

Light slows down. The individual photons don't.

Without reading the link, I can say that yes, it is possible. Proportional gain only will work to some level of performance.

But that's not a proper application of Newton's third law. If I apply a force, there will always be a force pushing back on me, regardless of the motion of the object. Pushing on a motionless object and having it not move is the result of some second force on the object. Motion of objects are the result of forces on them; the reaction force is exerted on me.

Because qV gives you the energy of the electron accelerated through a potential.

With the changes in demographics since the original observation, it's more like one born every 24 seconds.

The ice skating/medicine ball scenario is exactly what's going on in this case. The reaction force to SM pushing on the block is the block pushing on SM. Action/reaction pairs don't act on the same object (in this case, the masonry; action exerted on it, reaction exerted by it)

Yes, that's the virtual particle pair in QED, and how the interaction is modeled (i.e. the Feynman diagram); one of the links points out "A photon can fluctuate into any pair of charged fermions" — virtual particles are to what "fluctuates" refers. It's photon-photon scattering; that's what goes in and comes out. Otherwise you have to argue that electrons really don't scatter off each other because of the virtual photon that mediates the interaction. But that would just be semantics.

We have the original system out so we could play with it. The later incarnations are much more compact, as we had decided on a design. It's modular and fiber-coupled now; we have tried three different laser sources, and none of the optics had to be reworked — just plug in a different fiber. I'll post some more pics when I get back to the office.

If the cyclic models are correct, it won't be human action that made them so. If heat death is the end result, we won't be able to prevent it.

In short, NO. Mass and speed are not conserved quantities, massless particles have energy, heat is not a measure of particle speed, and sound is not a measure of pressure.

Terminal velocity isn't an absolute limit of speed, just the limit when the forces are limited to gravity and drag. Add in another force, snd the speed will change, so he could (in principle) do this. If the block had sufficient time and distance, it would slow to the terminal speed again afterwards.

old laser layout http://tycho.usno.navy.mil/clockdev/lasertable.jpg newer laser layout (the laser itself is in another part of the rack) http://tycho.usno.navy.mil/clockdev/Rboptics1.html

It was mostly DIO's (that's Direct Input Officer, i.e. directly from college to commission, for anyone trying to follow) for the first-half subjects when I was there. I met a guy who had gone through the program a few years ago (mid-90's) who implied that they had gone away from the DIOs and it was enlisted guys who had done a tour at sea who were teaching everything (when our XO had told him I was a former nuke instructor, he assumed I was former enlisted) And we had a joke about Direct Input Limited Duty Officers back in the day. Also "What's the difference between a seaman (or fireman) apprentice and an ensign? A seaman apprentice has been promoted once."