Concepts Definition and 412 Threads

hi, I was reading an article about graphene and I came across some concepts I am not familiar with. I was just wondering if someone could help me understand them: The article says that charge carriers in graphene are massless fermions that are described with a Dirac-like equation rather than...

Hello! I have just rediscovered this place since a few years back when I first signed up. This will be my first post, so forgive me if it is a bit long. I have been thinking about this for a while. So I have been thinking about buoyancy. I have learned that the buoyancy force is caused by...

Hello there, is there any computer software or programs out there that you can create various Faraday cages simulations

How plausible are these concepts? Thomas Ciesla's Centauri project utilizes a terraformed asteroid with antimatter propulsion that can travel at .30 c Alan Holt's interstellar transport system uses two field generators and 16 field amplifiers to create a space-time bubble around a vessel...

I am a mechanical engineering student who is taking his first chemistry class this upcomming semester. I have a question regarding water and its dilution principles. I have reading up on how Nuclear power plants work. I am curious to how the ocean water disolves and dilutes the radioactive...

My background in linear algebra is pretty basic: high school math and a first year course about matrix math. Now I'm reading a book about finite-dimensional vector spaces and there are a few concepts that are just absolutely bewildering to me: dual spaces, dual bases, reflexivity and...

Homework Statement High blood pressure results from constriction of arteries. To maintain a normal flow rate (flux), the heart has to pump harder, thus increasing the blood pressure. Use Poiseille's Law to show that if R0 and P0 are normal value sof the radius and pressure in an artery and...

Sorry if this is in the wrong section, but its not really homework, just curiosity. I'm a high school student struggling to understand a paper given to me, and search engines don't provide good starting points unless I have a more exact search query. The research is on star formation...

I would like someone to explain to me the correlations between these thermodynamics concepts: 1 State function/conservative force/reversibility 2 State function/exact differential Some functions in the phase space of a system are state function some are not. Is this simply an empirical...

If we have a circuit with one resistor in series with a voltage source like given in the link then at all points before the resistor the voltage is the same, and after the resistor the voltage at all points along the wire is the same, as there is no potential difference between two points before...

Heya, I'm a little confused about the heat equations and the difference in concepts and applications. So there's: Q = UA delta T <- I've used this for general heat transfer, like conduction through walls... Q = UA delta T(log mean temperature difference) <- I've used that for...

I was just reviewing some of my concepts of electrostatics, and I am really confused in some things. 1) Why does E equal the negative gradient of V? I understand the definition of the gradient, but in my mind I am just unable to grasp as to why it should be negative only. 2) Why is the work...

I'm a physics student (undergrad) studying Linear Algebra for the first time. I'm writing down my thought process, hoping that someone with more experience can verify my conclusions. I feel that the narration is more clear than my original attempt to present this as a series of questions. "A...

Homework Statement Which of the following are true for sinusoidal radiation? 1)The radiation pattern does not change with distance. 2)The radiation travels perpendicular to the electric field. 3)Oscillating charges are not accelerating. 4)The electric field and the magnetic field...

I've started reading Gerald Teschl's Ordinary Differential Equations and Dynamical Systems. I'd desperately like to crack these definitions from section 1.2: classical ODE, linear, homogeneous, first order system, autonomous, as they seem pretty fundamental. My plan is to give answers to the...

I have a lot of difficulty when solving problems. I usually don't know what to do, but once i see a similar problem I can follow the structure and solve problem. But i feel I am not learning anything. I've tried reading the book but i usually don't get it and stop reading because of frustration...

I want to know all about nuclear thresholds...where can i learn about them...? (e.g threshold energy and how particles behave under them...different types of threshold energy and their behavior)

Hey everyone, Just a quick question about a few electrodynamic concepts: 1) retarded time: t = t_r - (curly)r/c. Is t = total time, t_r = time elspased since the electromagnetic 'news' reached the point in question, and r/c = time taken to reach the point in question? 2) I'm a bit...

Hi Everyone, quick intro. I am taking thermodynamics (chemical engineering style, college) and am just generally confused by the concepts such as T, U, H, S, fugacity, etc, so I decided to revise my understanding and work my way up from classical physics. and I need some help with that. I...

Homework Statement An upward and downward pulse, otherwise identical in shape are propagating in opposite directions along a stretched string. At the instant they overlap completely, the displacement of the string is exactly zero everywhere. How does this situation differ from true...

I always fail to get the concepts down or not fully state the concepts, so I would appreciate it if someone reviewed my understanding of these concepts and point of the places where I'm not getting the right idea or almost got the right idea but not completely.1. What is wrong with this: "If...

Hi there, Physics lovers. I'm studying "The Classical Theory of Fields" from the "Course of Theoretical Physics" book series by Lev D. Landau, and I'm stuck with simultaneity in General Relativity. In page 251 of the Fourth "revised" english edition, by Butterworth Heinemann, There begins the...

Hi, I have a couple of questions for my general knowledge because I have a test coming up and I'm confused on some stuff 1) For an isothermal process is the \DeltaS=0 because \DeltaT=0? since it equals zero does that mean that the process is irreversible? 2)What makes a process...

Hello experts in diffusion, I am having some trouble understanding some concepts in calculating diffusion. First, I understand activity (or chemical potential) drives diffusion, but where does this come into play in the calculations? Is it in the activation energy (Q) in the Arrhenius...

I am really enjoying learning physics, and I am getting a thorough mathematical treatment of everything, but sometimes I find myself lacking an understanding of what many of the formulas and numerical results mean physically. My goal is to have a deep MATHEMATICAL understanding of how things...

Hi ! Can someone try to explain to me the general concept of potential well. I tried google, but i find it confusing with sea of equations... Thanks

3.A cylinder/piston arrangement contains 5 kg of water at 100°C with x = 20% and the piston, mP = 75 kg, resting on some stops. The outside pressure is 100 kPa, and the cylinder area is A = 24.5 cm2. Heat is now added until the water reaches a saturated vapor state. Find the initial volume...

I was thinking about the design of the Sikorsky X2 and S-69 concepts today, and I thought of an interesting idea. I am by no means an expert, but I guess you could say I know more about this subject than the average person. So anyway, if you know about the S-69 and the new Sikorsky X2...

1. A spherical capacitor consists of two spherical conducting shell centered at the same point, and their radii are R1 and R4, respectively. Between these two shells, a conductive shell with inner and outer radii of R2 and R3 is inserted, as shown in Figure 3. If charge the inner shell ( R1...

I'm trying this question. i know that resistance is the concept of ohms law together with electric potential giving rise to V/I but i can't seem to know how to start. Please advice A material of resistivity r is formed into the shape of a truncated cone of altitude h. The bottom end has...

Momentum, Speed, Acceleration 1. Which of these is constant when a charged particle is placed in a uniform electric field? http://img638.imageshack.us/i/lol025.jpg/ 2. If an electron was placed at P, would it accelerate toward D or E? If you can't see, the bottom left charge is +4q and the...

I was pondering about the following cases and I am wondering if gave a correct description for each case. Do tell me where I have gone wrong. Thanks! Case 1: When you travel near the speed of light and you observe a slow moving object. What do you see? -The object appears squashed (in 1...

I am stuck with some misconceptions about electrostatic potential/ potential difference. Please read what follows and correct me wherever I am wrong. Help appreciated. Thanks. :smile: Consider a dipole-like charge configuration (fixed at their positions by unspecified forces ) with the...

This has been bothering me for a long time. I hope someone in this forum will help me clear my confusions. So the way I approach mathematics is by working carefully over the concepts. I reread the concepts till they become crystal clear.( This has been painful for some of my classes like real...

Hey...i got a confusion @ how a circuit allows the current to flow initially when voltage source is applied across the capacitor.?? U know as per the concept the current flow in the circuit only if the circuit completes...? isn't it like that the dielectric between the plates of the capacitor...

Hello everyone, I'm new to the forum and I'm starting to learn about Relativity. I'm confused about a couple of concept that I've recently been reading up on. If two non-rotating spaceships are floating freely in interstellar space well outside the influence of any other objects in the...

I'm trying to study concepts of fusion...please help in any means possible...Currently I'm studying freidberg's plasma physics but want to know more...

Hi, I haven't done physics since year 10, and will be doing physics next year at college, it is involving the concepts i will list below, with a emphasis on the physics of the human body with them, so if it involves this it'll be great. I want a book that has fairly simple explanations, is...

Homework Statement A car with a mass of 1000kg is at rest at the base of a hill. It accelerates up the incline reaching a speed of 20m/s at a height of 100m.The work done by the frictional force is 450,000N. a)Calculate the change in kinetic energy of the car. b)Calculate the work done by...

It was suggested that this belongs in philosophy so I have moved as I was enjoying the thread. Anyone have any views? ...Is the universe an abstract concept. Is time an abstract concept? Originally Posted by TheAlkemist View Post Yes and yes. An abstract concept = A mental...

Homework Statement how come that if I grab a stone and attach it to a string and then rotate it along the xy axis it won't fall even though there is acceleration from gravity in the z axis where no force is applied? Homework Equations The Attempt at a Solution maybe its the fact...

Hi guys, I was answering some questions on my physics homework and I didn't understand why the answer was what it was... the first question was this: 1.) A hollow uncharged metal ball hangs from a silk thread. A glass rod has been charged by rubbing with rayon. When it is brought close to...

Homework Statement The transfromer equation is given by\frac{Vp}{Vs}=\frac{Np}{Ns} for an ideal transformer. This equation is correct only if there are perfect flux linkage, the resistance of both primary and secondary coil is small and carries negligible current. The notes mention here if the...

I would like to know of anything concepts regarding EMP. It's generation & how to sustain the pulse over long periods of time to create something like "no fly zones". Either to create a temporary block or permanent damage to any electrical items caught within the pulse radius. Also please...

Homework Statement Attached to my forum is my homework. I need help with #9 and #10. I have no clue on where to start. Anything is helpful Homework Equations The Attempt at a Solution

In algebra/trig. what kinds of problems have a domain and a range ? Is this true for anything that can be graphed? Because a lot of the time after you finish a problem in precalc. it then asks for the domain or range, so the question becomes, in mathematics, is it possible to find the domain...

Here I have a question which I'm unfamilar with. I'm not sure how to answer the question by explaining what is involved with the diagram. Discuss the following pictures in terms of work and power outlining any assumptions that you make.

Dedicated to products that work, but are worthless, wasteful, or silly. The inside-the-shell egg scrambler https://www.youtube.com/watch?v=chEPougF_nQ

Hi, I have a few things I don't quite understand in general relativity. In my course we have gone through a lot of mathematical stuff that I have blindly followed without really appreciating its significance and I feel bad about that. The first thing is, where did this idea of the curvature...

1. The use of a flimsy retort stand meant that when the pendulum was in the motion the retort stand was also swaying slightly. Explain this. 2. p=mv, torque=rmg 3. I am a bit stumped on this one. My teacher suggested I look into the torque of the pendulum - the friction at the...