Physical Definition and 1000 Threads

How much overlap is there between physical chemistry and chemical engineering with regards to thermodynamics, kinetics, and transport phenomena? Would it be beneficial for a chemical engineering student to take the physical chemistry courses that deal with these topics? Or would it be redundant...

We all know what it means to be homogeneous in a "hand waving" sort of way. And, of course, there are abstract mathematical definitions for a homogeneous space. I have been unable to find a physical measure of homogeneity which could be applied to a ensemble of particles, box of rocks, or the...

I only just discovered this today: http://what-if.xkcd.com/1/ I didn't know about it before. My question is simple: what do you think of Randall's analysis of the physics here? Is he "on the ball?"

I'm having a weird problem with my computer. I used to be able to leave my computer on for extended periods of time, and it would run fine. Now, I find that if my computer is on for too long, my svchost.exe processes get incredibly bloated and end up using 70% of my physical memory even when no...

I don't think it’s possible, but just wanted to confirm since there are some lofty IQ's floating around the forum that would know for certain. More of a fundamental Astrobiology question. Can we determine life 'from a distance' with a spectrometer or by any other means? I believe we have...

I have a little confusion in my head when I want to imagine time. Time is a bit more abstract then space dimensions for me. So I began from definition of time, and it is defined through motion of electrons in Cs atom. Therefore, I thought if the Universe was so simple, such that there are only...

For undergraduate college, would you guys suggest purchasing a regular graphing calculator such as an HP 50g or TI-Nspire NX CAS, or something like Mathematica 8 for Students at the same price?

[FONT=Lucida Grande]Hello everyone. [FONT=Lucida Grande]I wish to get the solution to the following: [FONT=Lucida Grande]x'(t) = [A*exp(B*t)-C]^(m) [FONT=Lucida Grande]I can get the plotted solution by Matlab, but I wish to find the analytic solution by myself. [FONT=Lucida Grande]Does anyone...

I keep hearing about new and more efficient batteries. Is there a hard limit on the amount of energy that could be extracted from a stored chemical energy source? Obviously the absolute maximum amount of energy would be given by E = mc^2, but I think that would be far beyond any...

I'm currently preparing for a classical prelim and am concerned that this problem may not be correct. I'm second guessing myself due to the hint given in the problem, which I did not use. Any help is more than appreciated. A picture of the pendulum is included. Homework Statement A...

How can we distinguish scalars from vectors?If we are given a certain physical quantity how can we justify whether it is scalar or vector?

I'm wondering if their are any unified physical theories that predict our universe to be a part of a multiverse in our own dimension? I'm looking for anything along the lines of stating that our universe is a star in a 'galaxy' of other universes that we can theoretically travel to if we could...

When a vector field representing a physical quantity (e.g. B) has ∇\cdotB = 0 what is then the physical interpretation of this? Some people have said that the field doesn't diverge away from anything, but as far as I can tell magnetic field can easily get weaker and weaker the further you go...

Hey guys, first post so be gentle. Just thought I would share this short skateboarding clip. Very impressive stunts done by Aaron Homoki (yes it's all real). I would be very curious to see what the physics community thinks about it. Is there a way to work out the maximum...

I have been reading on Galerkins method of weighted residuals according to which an approximate solution to a differential equation is expressed as: y^*(x)=Ʃc_iN_i(x) where i lies between 1 and n where y* is the approximate solution expressed as the product of ci unknown, constant...

Please forgive such a simple question, but how does a particle 'remember' what direction to travel in from instant to instant? I mean, say we take 2 particles way out in space, we kick one say along a +x axis, and the other with the same force along the -x axis... How is the Direction...

I am majoring in chemistry at UCLA with physical chemistry concentration (transferring as a junior next semester), intent on pursuing research in the field in the future. I would like to minor in mathematics (if a double major is not possible), but I'm having a hard time deciding what classes I...

I am trying to build a high frequency analog filter. I don't have the specs quite yet, but I do know how to create the transfer function. The trouble is, once I have that, how do I go about making this into a physical circuit? All the online stuff I can find is either digital or low frequency...

Hi! I'm studying special relativity and relativistic dynamics and I'm struggeling a little bit with the concept of 'covariance' of physical equations. As far as I understand so far 'covariance' is related to the 'form invariance' of the equations of motions in relativity and the concept is...

Most of the people here, who responded to the last thread posted by me, may think of me as someone who does not want to understand Relativity, and instead is just barking at the wrong tree. But I'm posting the same Logical contradiction of using Lorentz Transformation to conclude Time Dilation...

A little background: I am 22 years old, 3 years ago I got sick and lost a lot of weight. My physical condition deteriorated until I finally found someone who diagnosed me correctly (or at least correctly enough) and the physical deterioration halted. At the time I was in a lot of physical pain...

1. An electric space heater draws 15.0 A from a 120 V source. It is operated, on average, for 5.0h (hours) each day. a) How much power does the heater use and b) At $.10 per kWh, what does it cost to operate the heater for 30 days? 2. Suppose each person in the United States uses 12,000 kWh of...

Hi folks I know I'm becoming a bit of a frequenter on this board asking for academic advice, so here I go again. I've just finished a turbulent second semester at my university taking 5 courses at first before dropping Biology as I no longer was into it. I've recently been re-evaluating what I...

I found a website which claimed that 3500 feet of 35mm film was shooting at a maximum speed of 10600000 frames per second, to catch the first millionths of a second after the trinity explosion. I have an issue with how in the world this was done. I know that the camera exploded and the film...

Hey, I am new to this forum hoping that I can get some help with a project. I also hope to be accepted as a new member, hopefully learning from everyone here. I am sorry to ask a simple question that may be easy. I am learning and experimenting as a hobby, I do not have access to super accurate...

The continuous version of the Lorentz force is \mathbf{f}=\rho\mathbf{E}+\mathbf{j}\times\mathbf{B} but what does f mean? In the discrete version F is the force on the charged particle appearing on the RHS. So if x is the position of the charged particle we have that its equation of...

Homework Statement Two pendulums have the same dimensions (length ) L and total mass (m). Pendulum A is a very small ball swinging at the end of a uniform massless bar. In pendulum B , half the mass is in the ball and half is in the uniform bar. A. Find the period of pendulum A for small...

I know this topic has been addressed on this forum ad nauseam and please redirect my post if it is posted incorrectly. The basis for my view is that the scientific method will not be able to distinguish between different views which make the same observational predictions. I do understand...

We are starting to learn about spin in my introductory quantum mechanics course, and I was wondering if anyone could provide a physical interpretation of an electron's spin. I understand its a form of angular momentum which has nothing to do with the motion of the electron in space, but since an...

Dear All, When I have a equation 1/sT its an integrator with time constant i.e Assuming a T of 5s, if I input a unit step function, the output of the integrator reaches unity in 5 seconds atleast I undestand it that way. Please correct me if I am wrong in the same way can someone help...

hey , i want to hear your opinion on good books i could read . I just read "whats life? and mind and matter by Erwin Schröndinger , and I am looking for a book that tries to answer similar questions in a physical or philosophycal way , but from a different perspective, and with some...

Wikipedia: "Reynolds Number is a dimensionless number that gives a measure of the ratio of inertial forces to viscous forces." What is meant by the inertial forces? I have a much better intuition of viscosity. But it seems to be like the Reynolds Number predicts turbulent flow for a...

If I needed to describe a physical object it would be necessary to associate certain properties to it, properties I perceive as being related to this object. For example, when someone describes a massive soft blue ball bouncing in a white room what I would imagine is: a white background; a blue...

Is it known if space: 1. is "grainy" or smooth ?, 2. has singular points ?, 3. is like R^3 ?

Hey everyone, I'm brand new here, so please bare with me if my question doesn't come out right. Homework Statement So for my senior design class I am working with a control system that balances an inverted pendulum. Here is my SIMULINK diagram...

Given that the Classification Theorem says that every finite simple group is isomorphic to one of 4 broad categories of (specific) finite simple groups, does this mean that any conceivable symmetric: i) 2D form; or ii) 3D object is also isomorphic to one of these 4 categories. Otherwise...

I know how to use a commutator as a mathematical formula but I really don't understand what it means. Can anyone explain it to me. Is a commutator nothing more than a check to see if it commutes or not since I know that if you use a commutator with a wave function and the result equals zero...

"economic physical methods" for surface treatment of plastics I am a material science student, working on a plastic based composite (reprocessed polyethylene solid form, mixed with cement). Initially, the mechanical strength of composite was lesser, probably because of the poor bond...

Hi there! I saw this exercise that we have to calculate the covariant derivative of a vector field (in polar coordinates). Most of them equals zero, but two of them are non-zero, sugesting that this vector field is not constant. What i want to understand is the physical meaning of this values...

Homework Statement I trying to learn general relativity and ran into a few questions while learning about the expansion of the universe. I found a really good intuitive explanation of the expansion of the universe here: http://curious.astro.cornell.edu/question.php?number=274 However...

Reason I posted this in the maths help forum is that an equation of this form randomly popped up in a homework I was doing on differential geometry. I started with a one-form ω=dβ (β is a scalar function) and found that if for a random vector v, ω(v) = 0, then \frac{d}{dt} \left(...

Homework Statement This isn't strictly a homework question as I've already graduated and now work as a web developer. However, I'm attempting to recover my ability to do physics (it's been a few months now) by working my way through the problems in Analytical Mechanics (Hand and Finch) in my...

i.e. "A F = <0,0,10> is exerted at the point (1,1,1) what is the moment about the X axis?" i know the answer is <sqrt(3),sqrt(3),sqrt(3),> DOT (<1,1,1>x<0,0,10>) but the physical meaning of that escapes me. in what applications would an axis be more useful than a point? thanks!

How many meters will light travel in 83.8 hours? what I came up with is (3x10 m/s) (83.8hr) = 2.5 14 x 10 answer 2.5 14x10 m teacher marked it wrong very confused.

Physical laws ... are they material?! There was an old question about physical laws , where do they come from? as they are considered separated from the material of the universe. Of course I know that they are produced by the human brain or human consciousness (which is material in turn) , but...

Hello PF! (Not sure this is in the right section.) I've learned very little about maths/physics in school, but went back to uni last year to do maths. Physics is still a bit of an alien territory, but nevertheless I like exploring it in my own amateur way. One of the things that started...

As far as I have seen, all physical models begin with space, and then put matter that live in space and modify it somehow. Basically the models works fine and describe reality farily well. But at some point they arrive to problems, as infinite curvatures, that prevents them to be unified. It...

Hello experts (or even the not so experts) in QFT. Have you encountered before the following stuff on QFT? http://www.scribd.com/doc/58635278/Introduction-to-a-Realistic-Quantum-Physics The following is an example of what it's saying: The basic idea is that: Please find critical...

I was wondering what were the fundamental physical units of measurement, ie those from which all other units can be derived. To my mind, there are only two things which exist in the universe and from which all units of measurement can be derived : space and matter. The reasoning is as follows ...

How does a CPU send information to memory locations - physically? I know in software you can reference memory locations. I'd like to know how a CPU references them? I understand that it symbolizes a memory location using bits (00000101 = 5) but - how does that string of bits work in the...