Physical Definition and 1000 Threads

hi, I am a novice to quantum mechanics and get a lot of troubles with operators. I cannot explain why: - why QM uses operators for observables such as position, momentum, energy, ..ect, but classical physics does not? - what are physical interpretations of operators? - why are operators needed...

Homework Statement What physical and chemical changes occur when a wax candle burns? Homework Equations The Attempt at a Solution

We know the the generalized momentum is P=mu + qA Can someone explain to me, what's the physical meaning of the quantity 'qA'? The particle's momentum that we measure is just 'mu', right?

1. A square object of mass m is constructed of four identical uniform thin sticks, each of length L, attached together. This object is hung on a hook at its upper corner. If it is rotated slightly and then released, at what frequency will it swing back and forth? Homework Equations...

physical pendulum--thin rod Why do you have to divide the length L by 2 in these cases? The explanation that's provided in my book says "the distance L between the pivot and the center of gravity is .5 the length L." This makes no sense whatsoever. The length should be the same regardless of...

I, as with Albert Einstein, shall always side with Issac Newton; that is to say, that light is corpuscular. There is no such thing as a light 'wave'. Sure, Thomas Young threw the world of physics a curveball in 1802, backed by Huygens and his somewhat sound reasoning (for the time). But who...

Hello. Today I came across a physical phenomenon .. I played badminton in France, at the swimming pool. So I lost my paddle in the pool. (A badminton racket looks like a tennis racket) In the water, no matter how I throw the racket down, balancing it on the head in the bottom of the pool...

in the nodal analysis -one of ways of analysis DC circuit - i couldn't understand the physical roots of this way . i mean how could i make the voltage of a node equal to zero by make it as a reference point without having any effects on the voltage(electric potential) of the rest nodes ...

My understanding of how AC current works is that the current changes direction, so essentially the charges are oscillating back and forth along the direction of the cable. Then since accelerating charges radiate, this produces an EM wave which is what carries the energy. But my problem is...

I just finished my first Linear Algebra class and loved it. There is one thing we didn't go over much though. What exactly IS a determinate? Is there a physical interpretation? Or is it just an operator that has these special properties? Thanks! ~Matt

What would happen to the universe if the physical constant of Big G was changed?

http://www.cbsnews.com/stories/2010/06/10/60minutes/main6568387.shtml?tag=contentMain;contentBody" https://www.youtube.com/watch?v=<object width="480" height="385"><param name="movie" value="http://www.youtube.com/v/FZUzB8uC9bs&hl=en_US&fs=1&"></param><param name="allowFullScreen"...

Im planning on taking physical chemistry in the fall. My G. Chem has always been strong, but this past spring I took modern physics (using Taylor/Zafiratos) and feel like I have A TON to learn. So this summer I want to study up the materials where I feel weakest at: FOr Diff Eq's I am...

I was wondering whether any members of this PF sub-forum would help me towards some physical interpretation of Maxwell’s time-dependent equations, which must ultimately underpin any classical description of EM wave propagation. I know that some might simply suggest reading a good textbook, but I...

Ya know, rare Earth magnets and crap like that. Anybody know of some other cool things to have sitting around the house?

Hey guys! When I was on a trip in Cambridge I took a picture of the famous apple tree, that is supposed (so the turist office claims:-p) to be the one, where Isaac Newton got the idea for his most importaint work. In the back there are two windows and one of them (I think it's the right one)...

I wanted to hear suggestions for the...roughly...5 most essential physical problems that a serious working physicist should understand how to solve. Like the conceptual goals for someone who is just getting into the center of my study of physics (headed towards graduate school in a year.) Thanks...

Homework Statement Compute the \mu=0 component of the Minkowski force law K^\mu=q\eta_\nu F^{\mu\nu}. (Einstien summation convention applies.) Homework Equations \eta_\nu=\frac{1}{\sqrt{1-u^2/c^2}}(-c,u_x,u_y,u_z) F^{\mu\nu} is the field tensor where...

I am required to simulate the propagation of a the wavefront produced by a laser light (about 633 nm) passing through a system of lens and undergoes a few reflection. What I did at the moment is to do ray tracing, record the optical path length of each ray, then connect every point of the same...

Homework Statement Ok worked out the time period of a physical pendulum (T) to be (in terms of constant a, and variable length x): T^2 = 4pi (1/2a^2 + x^2)/(gx) Now asked how i could use a measurement of T(x) to measure g. Homework Equations The Attempt at a Solution I...

Hello. I am making a small induction motor and have been wondering about it's limits. I have googled a lot and can't find a helpful answer. Is there a maximum length of coil that a magnetic flux of specific strength can excite ? Thank you, Gary.

I was reading about products of inertia in my dynamics book, it was defined really well, however it did not explain the physical meaning of the product of inertia. Is it still resistance to rotation? However products of inertia can be negative. Are they simply mathematical artefacts with no...

Homework Statement Two ports along a coastline are 300 km apart. One port has high tides 30 minutes later than the other. How deep is the effective depth for the tidal propagation? Homework Equations I am thinking I need the following equation: V = square root (g*H). V = velocity. g...

I want to dig a little bit into the idea of geometry and how it relates to physical theorization. It is my feeling that there is profound ambiguity as regards the "ontological status" of geometry, and that this ambiguity only serves to muddy the waters as far as the way in which mathematics...

Hello, I am going to be taking the ACS physical chemistry exam in a few days and am trying to find out the materrial that will be on it. The ACS website leaves out a lot of stuff in there description.

I am taking an undergrad course P Chem II: Quantum Chemistry and Spectroscopy...and the final is a standardized exam from the ACS. I was just wondering if you guys had any tips or knew where to find old exams to practice with. I just was looking for any advice in general too. Thanks a bunch!

Homework Statement The typical walking speed of a person walking at a relaxed pace can be estimated by modelling their legs as a physical pendulum. Assume that the length of a person's leg is L and it pivots about the hip and the leg is tapered (more mass towards the hip and less towards the...

When monochromatic light propagates through a material other than a vacuum, we observe that its phase velocity has moved away from c. By relativity, we know that massless particles like the photon must move at the c however the pragmatics of classical optics ask of us to overlook this fact in...

Hi Guys, I seem to have gone in circles YET AGAIN! When discussing the expansion of the Universe I was told by friends that masses and objects do not expand with space because the forces within the mass are so much stronger than the inflationary force. When discussing General relativity we...

Homework Statement The motion of various shaped objects that bob in a pool of water can be modeled by a second order differential equation derived from F = ma. The forces acting on the object are: 1)force due to gravity, 2)a frictional force by water, 3)and a buoyant force based on...

I've been trying to think of a really good experiment in which the data gathered would be non-linear. The only ideas I've managed to come up with were either way to simple and boring, or way to hard for me to set up and measure accurately. Some examples of experiments include splash radius of a...

exam practise question: what are the physical observables determined by the quantum numbers n, l, ml and ms of the electron in a hydrogen atom. most places just give the equation or the name not the physical observable determined. so is this right?:- n = principal number determines the...

Homework Statement 5. [1pt] For each of the following, indicate whether the statement describes a physical (P) or a chemical (C) change. Answer, in order, with a single string, e.g. CPCPC -- NO SPACES, NO PUNCTUATION. a) A grease spot is removed with cleaning fluid. b) Sodium...

Do you think it would be possible for a ipod sized device or small notebook to project an image rather then have an actual screen? So you could carry it in your pocket & when turned on the desplay could be massive like 50inches. Something holographic or what youd expect in the movies...

I have always had trouble appreciating E=mc^2 because I can't relate C^2 to a physical process, like velocity or acceleration. How should one imagine the dimensional characteristics of C^2? Along the same vein, is E=mc^2 a mathematical conversion only, or does C^2 describe an actual process by...

Why does the laplacian vanish for harmonic functions? Can someone explain this in physical terms?

Maxwell: -"The ratio of m to mu varies in different substances; but in a medium whose elasticity depend entirely upon forces acting between pairs of particles, this ratio is that of 6 to 5, and in this case E^2= Pi*m" Q1: What is this 6:5 ratio and how did he make that conclusion? Q2: What...

Homework Statement A stick of mass M, length L, stands upright on a table, pivoted to the table. What is the angular velocity as it hits the table? Homework Equations ang. accel = (3g/2L)cos theta w = (3g/2L) integral cos theta dt The Attempt at a Solution theta (t) = ...

Homework Statement A stick of mass M, length L is standing upright on a table, pivoted at the bottom. What is its angular velocity as it hits the table? Homework Equations ang. accel = (3g/2L)cos theta (theta is zero with stick laying on table) The Attempt at a Solution...

All -- With a meter stick standing straight up and pivoted at the *bottom*, what is the final angular velocity as it hits the table? I've found plenty of standard stuff on physical pendulums (meter stick pendulum), where I = 1/12 MR^2, period, etc, but I can't find velocity info...

hey, What is physical intuition? How do we use it in physics?

"physical" degrees of freedom Starting with the Lagrangian for EM, it looks like there are four degrees of freedom for the four-vector potential. But one term is not physical in that it can be expressed completely in terms of the other degrees of freedom (so it is not a freedom itself), and...

Hi, I've just been thinking (saw another thread about light). Is light a physical item (Ie a brick..- Though on a atomic level).. what causes light to go "fast", & as it hits us, why aren't we crushed with all the weight ? (or is light weightless ?? ) as light doesn't pass through...

I understand that certain vectors in space-time (spacelike vectors) present a non-causal situation where E2 which takes place at a time after E1 in the rest frame cannot physically be a consequence in a different frame at sufficient speed. but there is also the relationship that arises from the...

No, I don't mean the kind where you use equations to describe physical systems, I mean the kind where they take your picture. People have often told me that I could be a model if I wanted to be and probably make good money doing it. The whole idea of doing any kind of modeling repulses me but I...

My doubt is on the angular wave number 'k' in case of a sinusodal wave on a string, the angular wave number k = (2*pi)/lambda lambda being the wave length of the wave. What does 'k' signify in physical terms ? for e.g. general wave number = 1/lambda again, lambda being...

I'm not sure whether to just take Physical Chemistry because I'm interested in it or should I just take Quantum Mechanics? I've already taken Thermodynamics and I heard P-Chem is Thermo and Quantum combined. Is Quantum more in-depth than P-chem?

Hi all, Sorry if this is a dumb question, but what exactly do we mean by the term parallel transport? Is it just the physicist's way of saying isometry? Also, in my class we have just defined geodesics, and we're told that having a geodesic curve cis equivalent to demanding that the unit...

what is inductance?...i need a physical meaning and not equations!

Homework Statement A sample consisting of 1.0 mol of calcium carbonate CaCO3(s) was heated to 800°C, when it decomposed (CaCO3 → CaO + CO2). The heating was carried out in a container fitted with a piston which was initially resting on the solid. Calculate the work done during complete...