Physical Definition and 1000 Threads

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...

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 I've gone out and measured my changing weight in an elevator using a bathroom scale, taking measurements each second, with the elevator ascending 4 storeys. I am wondering if it is possible to work out the acceleration of the elevator from these results, and if so how they...

i have some question about lagrangian ...here are those 1) what is the physical meaning of L=0 .. from wiki ..i have found .."The Lagrangian, L, of a dynamical system is a function that summarizes the dynamics of the system." that means when L=0 ..the system has no dynamics ..as far as i...

Hi =D I was thinking about the physical units (g, m, s, K, J, A, V, etc). I know we got a thing in physics called dimensional analysis, so you analyse some variable that you know it depends on other variables and the two sides of the "equation" (I mean a equation with the proportional sign...

My understanding of a modern computer is as follows; 'information' is sent from a keyboard as current (I), this signal is sent to the CPU via the appropriate buses (in this instance, USB -> North Bridge -> main bus/cpu bus -> CPU), which is then recognized by a CPU via integrated circuit, and...

I am wondering if there is a physical interpretation of the Laplace operator (also known as Laplacian, Δ, ∇2, or ∇·∇). From my impression a gradient of a function is the vector field in the direction with the greatest change. Also a divergence is volume density of flux from a point source...

I would like to know how can parity be physically interpreted :confused:?

the physical meaning of the PDE?! Homework Statement http://agentsherrya.jeeran.com/qu.JPG Homework Equations How can I know the physical meaning of the following partial differential equation?!

I have so many fundamental questions about physics, i hope they are not considered "speculative" and deleted... Physics convolutes things so much, i wonder what does physics define as a physical property. For instance - an electron has a property (quality) of charge. Hopefully - this means...

Hi, Would appreciate any help anyone has for me. I am building a physical pendulum of sort, which consists of a hollow cylinder, which I am going to fill with sand. I am going to let the sand flow out of the pendulum and investigate the change in period with changing mass. I also am...

I have always been confused by SR and GR in terms of what each observer observes of their own frame of reference. e.g. Does an observer moving at a high v/c measure length contraction in their onw F of R? I assume not since all apparatus would be similarly contracted. Nor do they measure...

As though they also have a mental disability?

I'm doing some senior research into caching algorithms. In order to effectively evaluate some of our algorithms it would be amazing if we had access to physical addresses sent from the CPU to the memory captured in real time under real operating conditions. Does anyone know of a place that might...

What kind of air or water pressures can a human withstand? Approximately when does it become difficult to breathe and eventually impossible to breathe? After this point, would the person being succumb to these extremes be able to hold air in their lungs? What would be the first factor to cause...

Can man-made EM waves produce physical vibrations of objects? Can man-made EM waves vibrate powders like sand or talc? I'm trying to understand if any types of electronic frequencies can cause physical vibrations...thanks.

I don't understand why an x boost followed by a y boost is different from a y boost followed by an x boost. Surely only the resultant velocity matters, and isn't time reversal a symmetry of SR? Similarly, why is the matrix for three simultaneous boosts any different from the product of boosts...

Hello all, I've just started a class in physical chemistry and it seems to be progressing fairly slowly so I thought I'd start a thread so we could discuss some key concepts that are frequent in physical chemistry. Keep in mind I haven't taken any courses in thermal dynamics yet so I am...

This is not a homework problem, I'm going over some notes and seem to have a discrepancy. In a local region with no charge, del.E=0. Since the divergence is zero, there are no sources and sinks (ie charges). In my notes I have; "In cartesian co-ords, a solution of del.E=0 is a uniform...

Just curious, are there any?

it's konwn to all that laplace equation in 3 dimentions have clearly physical meaning,how about that in higher dimentions? I first thought that had something to do with relativity or quantum mechenics with higher dimentions ,but it is hard to figure it out . can anybody explain that ,thanks a lot

The quotes below (in blue) are from another thread https://www.physicsforums.com/showthread.php?t=364893&page=5" , but since they are a slight digression from the topic of the original thread, I have decided to continue the conversation in this new thread. Yes, that it what I am talking...

Hello How are u ? please help me What is Physical Principle for CT ( Computed Tomography ) ?

what actually happens physically ...when we make transpose of a matrix...and in unitary transformation we transpose the matrix and take the conjugate...physically what type of change happens in it.

If the universe is shown to have angular velocity, is this evidence of a physical universe prior to the "Big Bang"? Several studies are being undertaken currently to determine the rotational velocity of the universe. So far they have all indicated a positive velocity although the values...