A small coin, initially at rest, begins falling. If the clock starts when the coin begins to fall, what is the magnitude of the coin's displacement between t1 = 0.188 s and t2 = 0.845 s?

You're a consultant on a movie set, and the producer wants a car to drop so that it crosses the camera's field of view in time t. The field of view has height h. Derive an expression for the height above the top of the field of view from which the car should be released.Express your answer in terms of the variables h, t, and appropriate constants.

on the wikipedia article about the equivalence principle there is a mention about testing the EP against parity-violating masses;

"The equivalence principle is untested against opposite geometric parity (chirality in all directions) mass distributions. A parity E

I'm interested in the meaning of the phrase "continuum limit" specifically as it is often used in expressions relating to the ability of a quantum gravity theory to recover GR in the continuum limit.

I believe I understand the meaning but want to make sure I am not missing some important part of the precise definition as my intuition may be off and I have not seen it defined anywhere.

Pointers to a place where it is defined in an online resource would be appreciated. A google search just turned up many references to it being used in papers and articles and such.

I recently heard about jet quenching concerning data taken by the experiments at the LHC. Apparently it is related to the existence to the quark-gluon plasma. As far as I understood this interpretation is an analogy to hydrodynamics (the jet is "blocked" by the plasma).

I would like to understand that in more details: why is this analogy a "good" one, how far can it go and how do we detect that experimentaly.

There are many stories about radioactivity and the relative danger of it in the news lately, but very little actual information. The radioactivity levels around Fukushima Daiichi are high, but seem negligible in just somewhat removed locations.

The real danger seems to stem from ingesting radioactive particles. Just how likely is it for that to happen in any considerable distance from the reactor, say in Tokyo, and how dangerous for the human body is it really? How far can these particles travel in any dangerous concentration?

Is it something unexpected?Why universality in cold atomic gases is important?What researches are looking for?Can this be useful for topological quantum computers?

Can we expect a whole myriad of these states?

http://arxiv.org/abs/1012.2698

thanks

There have been a lot of sci-fi shows recently using the "rotating space station" explanation for gravity on space stations.

After watching these videos:

http://www.youtube.com/watch?v=49JwbrXcPjc&NR=1
http://www.youtube.com/watch?v=_36MiCUS1ro

I was wondering what would happen, if you were facing the direction of rotation, while standing on the "floor" of a rotating space station and tossed a ball "up". From the video it looks like the ball should land in front of you. Is this in fact what would happen and if you dropped a ball would it land behind you?

Extending my previous question Angular moment and EM wave, does it make sense to talk about the angular momentum of electromagnetic waves in an anisotropic medium? It is not obvious that the angular momentum is conserved in this case. However, if the anisotropy is introduced by the external magnetic field (eg, magnetized plasmas), the projection of the angular momentum of a wave packet on the direction of the magnetic field might be conserved

Just wondering about the definitions and usage of these three terms.

To my understanding so far, "covariant" and "form-invariant" are used when referring to physical laws, and these words are synonyms?

"Invariant" on the other hand refers to physical quantities?

Would you ever use "invariant" when talking about a law? I ask as I'm slightly confused over a sentence in my undergrad modern physics textbook:

"In general, Newton's laws must be replaced by Einstein's relativistic laws...which hold for all speeds and are invariant, as are all physical laws, under the Lorentz transformations." [emphasis added]

~ Serway, Moses & Moyer. Modern Physics, 3rd ed.

Did they just use the wrong word?

I'd like to create a very rough animation of a wave crashing on a beach. I'm guessing it would have to be a particle simulator, where you code in the forces between the particles and then integrate forward in time. I've done similar things, like simulations of charged particles, but there the forces are pretty straightforward, whereas here I guess I'd have to account for 1) tides 2) gravity 3) water surface tension. These seem like widely different forces acting on different scales. I don't even know where to begin. Any hints or links to papers related to this topic?

illustrated a procedure to forecast the decay rates of isotopes with known long average lifetimes. Lifetimes of the many U isotopes vary from micoseconds to gigayears. F has only one stable isotope while Sn has 10. Can Standard Model principles be used to predict the stability of isotopes and the average lifetimes for unstable isotopes, or can this only be done by measurement?

I need to create an online service displaying latest Kp index.

Where I can take the data?

The data should be in machine-readable format, i.e. text files, XML, or CGI gateways, for instance. No graphical plots!

I found this: http://www.swpc.noaa.gov/wingkp/wingkp_list.txt

Is Est. Kp what I need? I compared the data with plots covering several last days and found that kp values in this file are lower that on the charts.

A-Calculate the speed of a proton after it accelerates from rest through a potential difference of 220V .

B-Calculate the speed of an electron after it accelerates from rest through a potential difference of 220V .

I'm interested in the extent to which quantum physical effects are seen at a macroscopic level. I might get some of the physics wrong, but I think I'll get it close enough that I can ask the question:

Let's sat that we create a bonfire and let it burn until it burns out. As the smoke rises from the fire, turbulence takes over and the smoke particles and steam and hot air all mixed together. By the end of the night when the fire has burned out, the collection of molecules in the system are in some position/velocity X.

My question: Let's assume the multiverse interpretation of quantum physics. How many possible end state superpositions can there be in this situation? Ok, that's imprecise and incorrect because it would actually be an uncountable infinitude of possible end states. How about this: Given the end state that we observed, what percentage of the end state superposition would be "visually" indiscernable from the end state that we observed so that each molecule would be in nearly the same end state across that portion of the multiverse?

Or put another way: Do quantum effects sneak into everyday life fast enough that we can observe them? If we are effected by quantum physics at all, I imagine this is roughly a function of the timescale of the chaos effects.