Physical Definition and 1000 Threads

What is the physical meaning of raising/lowering indexes? From a mathematical standpoint, I clearly understand what an expression like v_a = v^bg_{ab} means. But let's assume that v^a is, say, a 4-velocity: can I say that v_a is a 4-velocity as well? Or is it something different? Not to...

I have recently been reading on the topic of the philosophy of relativity and the nature of spacetime. An interesting example of the difficulty of understanding the physical reality of the relativity of simultaneity has me very much at a loss to explain how the theory of relativity really...

Hi to all, I've to write differential equation for desciribe system in attached file. The system is intended: from force f as input to position x2 as output. Initial condition are the following x1=0 and x2=0. In the attached file I've included all formula for descrive relationship between...

[SIZE="3"]1. Homework Statement Hi, I've been thinking about a formulation regarding "physical quantities" (that is, the quantities that specifically constitute the object of measurement for Physics), energy, and the conservation of energy. It would be very helpful for me that you could...

Homework Statement a hoop of radius R=.18m and mass=.44kg is suspended by a point on its perimeter. If the hoop is allowed to oscillate side to side, what is the period of oscillation? Homework Equations I=MR^2 plus an offset? MR^2 so I=2(MR^2)? PE=1/2kx^2 w=(2pi)/T KErot=1/2Iw^2...

The metric due to the gravitational field of a spherical mass is described by the schwarzschild metric ds2 = c2 (1 - R/r) dt2 - (1 - R/r)-1 dr2 - r2 d\Omega 2 Where \Omega is the solid angle, and R is the schwarzschild radius. What are the physical meanings of the coordinates t and r...

Physical state to subjective "Qualia" and evolution - why? I'll try to make the points I'm getting at as concise and clear as possible. We all have sensations/emotions of pain, joy, hot, warm, cold, fear, curiosity, and the direct senses of light, sound, etc. Let us for the moment...

Hey all! Just a very short question: May I interpret the Lorenz invariant quantity \bar\psi\psi as being the probability density of a fermion field? Thanks! Blue2script

What effects do the physical properties (size of atom etc.) of an elemental metal have on the threshold frequency for that metal? I haven't been able to find a correlation between a physical property and the size of the threshold frequency myself; maybe I haven't looked hard enough, or maybe...

We keep searching for the Physical Laws but is anyone looking for the Laws that brought them about? Is it not inconsistent to expect Physical Laws to have no cause? Foundations of The Quantum Logic

This is the question i have to answer... And i really need help with it! Please help me=) If equal masses of iron and water absorb the same amount of energy, then which one of them will have a smaller temperature change? Thank u! Daniel!

Homework Statement A long, straight, and massless rod pivots about one end in a vertical plane. In configuration I, two small identical masses are attached to the free end; in configuration II, one mass is moved to the center of the rod. What is the ratio of the frequency of small oscillations...

Hello I want to ask for something I have a theory and I want to write the equations for this theory How can someone invent a physical equation? I didn't find any sites on the internet Are there any resources about equations and their philosophy? Thank you

Books to build "physical intuition" All physicists say that it is very important to have this thing called physical intuition. I have a general idea what it means but I don't quite fully get the subtleties between physical intuition about a topic in physics versus understanding the equations...

I know that placing a paramagnetic molecule inside a magnetic field will induce a magnetic force on the molecule from the unpaired electrons, but what will the effect be on the physical properties on the molecule (of any?) Specifically will the size of the molecule be changed? My understanding...

Can someone please explain to me why it is that the direction of a cross product is perpendicular to the plane of the original vectors? What is the physical significance of this? I mean, if I take torque as an example, what the hell does it mean to say that the direction of the torque is...

Homework Statement Can anyone verify what a physical quadrapole looks like? I'm trying to do a multipole expansion on one Homework Equations I understand what a physical dipole is and how to do a multipole extension on one The Attempt at a Solution My best guess is that a physical...

When I take the fft of a set of data and plot it, there is a reflection around the nyquist. Everybody knows this, but I would like to know what the physical meaning of the second half (the reflected half) is. The real component is the same as the first half, and the imaginary component has...

Hi, I've used complex numbers before for contour integration, circuit theory, and analysis; the only problem is, I have no idea how to think of complex numbers, physically - no teacher, book, or website seems to offer me any adequate solution. Can anyone please help me ? I hate doing...

Calculate the final temperature of a sample of carbon dioxide of mass 16.0g that is expanded reversibly and adiabatically from 500mL at 298,15K to 2.00L. I know the answer and understand how to do the problem except for 1 part. The equation to get the solution is : Tf = Ti (Vi/Vf)^(1/c)...

this is one of my pchem class homework... and I have no idea how to solve this... compute \tau for and electron in the double square well potential of width L = 2 Bohr, and depth \bar{V} = 4 and separation R = 3. Use atomic units for your computation... and in his lecture notes... he gave...

Hi! I would appreciate your thoughts on something. :smile: Let's say you have a ring with radius R rotating with angular velocity \omega about a vertical axis. A little bead is threaded onto the ring, and the friction between the bead and the ring is negligible. The bead follows the ring's...

This is a quick question. Is it correct to say that the change in color of iron to a reddish-brown color when the iron rusts is a physical change?

I know,that my question is bizarre,but i m interesting for answer. To create formula,i mean,that scientist makes experiment and formula is result of it.And I have sometimes problem to understand,what physical formula means. For example:Average speed is simple to make scheme.Just speed...

I suddenly realized that the very notion of a directrix seems odd to me. (1) I don't know any physical significance of such a thing (2) How anyone came to define the parabola as such Any help? I read some older posts about the history of the directrix/focus definitions of the conic...

Hello, What is the physical meanining of rational and irrational numbers? In the same sense, what is the physical meanining of complex quantities? Thanks in advance

In the past I have worked with scalar and vecor fields. I get vector fields. at each point the field has a magnitude and direction. With tensor fields, from what I have seen in diagrams, each point has three vectors assigned to it, and they appear to be orthogonal to each other. What is the...

I am wondering if anyone knows of research being done, or theories that are related to the actual structure of space-time as they are related to physical constants such as the speed of light, Planck's constant, and the cosmological constant. I'm far from being a expert, but I've been playing...

Hello friends. I simply couldn't find an easier way to explain what I'm looking for, so here's a drawing. And my questions are: 1. Does something similar even exists, and how is it called? 2. With the proper masses/ratios/calculations/whatever & control system, is this device able to...

Hello There, I'm a senior at the University of Illinois Chicago, studying mathematics and chemistry; I'm at the point where I need to become familiar with a computer programming language that will not only be useful down the road but help with the admission process into graduate school...

Can the circulation about some closed (rigid) path in a force field be interpreted as the work done by the force field on the path over an infinitesimal time?

i have read about wigner rotation but i think i can't understand it well , i want to know the physical meaning of it .

What physical quantities are these differential forms in classical electrodynamics? I read the paper ofhttp://arxiv.org/abs/physics/0005084" (A gentle introduction to the foundations of classical electrodynamics: The meaning of the excitations (D,H) and the field strengths (E, B)). The...

Homework Statement at 20 degree celcius, the solubility of a solid substance x in water is 42g/L. There are 3 solutions containing x kept at this temperature: S1 contains 5.1g/L,S2 contains 39g/L, and S3 contains 57g/L.so, how to make a saturated solution containing 45g x per litre overall for...

Abstract This post introduces a holistic approach to the description of the physical reality. The solution, referred to as the Dynamic Universe (DU) [1], is based on a zero-energy balance of motion and gravitation in spherically closed space. The Dynamic Universe allows the derivation of all of...

at 20 degree celcius, the solubility of a solid substance x in water is 42g/L. There are 3 solutions containing x kept at this temperature: S1 5.1g/L, S2 contains 39g/L, and S3 contains 57g/L. if we want to make S1 saturated with x, is it possible that we can add an equal volume of S2 and S1...

Homework Statement A rigid container,maintained at 50 degree celcius, is evacuated by a vacuum pump. After this, some liquid n-propanol is introduced into the container. part of the liquid will flash off inside the vacuum,but eventually the system will settle into equilibrium. what is the...

I have maintained here several times , amid howls of objection from a few, that spacetime IS something more than a mathematical construct or that at least we should maintain an open mind about that possibility. I have been thinking WHY I have that view and a significant reason is the presence of...

Hi there, In all text of QM I have, they tells that the density operator is hermitian. But without considering the math, from the physics base, why density operator must be hermitian? What's the physical significane of the eigenvalue of density matrix? Thanks

I wasn't quite sure which forum to use for this, as it covers QM, relativity and geometric algebra, but I'm trying QM for a start. The Dirac equation can be expressed surprisingly simply in the Algebra of Physical Space, as has been shown by W Baylis, and I worked the same thing out...

Hello, I'm currently living in Florida, but I'm planning to stay at my aunt place in New York for a couple of weeks this summer. Also, I'm no longer living in the apartment where I was living and will be looking for one while staying there. I'm applying for jobs these days, and I'm wondering...

Homework Statement how can i have a feel of pressure ... i mean how much is 1 psi and how much is 10 psi pressure ... can you please give an example ! Homework Equations i think pressure = force / area but still i don't undersatnd how much is 1 Newton ... i mean i don't get a feel of...

I am having trouble clearly/completely understanding the main cause of a transfer of thermal energy into the environment as a result of a bond formation. In terms of a very simple, generic, exothermic reaction... What I know...I can picture the atoms coming together through electrical...

Given the volume of a sphere V is given by V=\frac{4}{3}\pi r^3 Taking the derivative of the V wrt r gives \frac{dV}{dr}=4\pi r^2 which is the Surface Area of the sphere: \frac{dV}{dr}=A_s Taking the derivative of As wrt r gives \frac{dA_s}{dr}=8\pi r which I don't recognise as...

Hi I'm trying to get an opinion if Mathematical Methods in the Physical Sciences by Mary Boas is a good book to learn physics mathematics with a background in Calculus. I've been seeing people like it as a reference book, not so much as a learning tool. Opinions? Thank you

http://www.eurekalert.org/pub_releases/2009-07/lu-pro070309.php Well, according to this article, at least. http://www.sciencemag.org/cgi/content/abstract/1174962 Just thought I'd share. Problem is, they didn't entirely describe high temp superconductivity. O well.

Currently we see to about 15 billions years, determining that to be the edge of the universe. Could that just be the limit of what we detect can travel? It experiencing "friction" or other obstacles along it's travels.

I was reading on the net about 800m distance running to try and improve myself in the event, and then happened to come across this ~ Yes I know this is common sense and again backed up by medical science's experiments on lactic acid build-up and also since the professionals are far from...

Homework Statement A uniform circular disk whose radius R is 40.0 cm is suspended as a physical pendulum from a point on its rim. (a) What is its period of oscillation? (b) At what radial distance r < R is there a point of suspension that gives the same period? R = .40 m g = 9.81...

Imagine, You have dug a hole clear through the Earth. From one side to the other. Don't ask me how, you just did. Let's pretend that the hole is totally perfect: Same diameter thoughtout, no cave-ins, and it somehow doesn't get hot or filled with magma in the center. It's just a clear shot of...