Basics Definition and 371 Threads

What is a wave, phase, phase velocity and group velocity? I don't need the defination but understanding in such a way that i can form an image in the mind.

Right, I'm sure this is bread and butter to a lot of you but I have just been introduced to the SFEE. mgz+0.5mC^2+H +Q = mgz + 0.5mC^2 +H+W Where Q is the heat transfer, W is work done and H is enthalpy. Where is it assumed that the heat energy is in the energy balance? If heat is added where...

Why is Vab = Van -Vbn? I'm doing this after a while so maybe I'm getting something basic wrong but surely the potential difference between lines A and B is the voltage drop across phase a (Van) plus (rather than minus) the voltage drop across phase b (Vbn)?? So Vab = Van + Vbn? Thanks

I need help. I have no physics background so need the simplest of answers. I have a question to answer - about the damage that might be caused to a person falling 0.4m off a step. The questions doesn't ask for specific calculations but ask for concepts of force, acceleration and gravity to be...

Homework Statement Hello people, I am trying to understand a problem statement as well as the density operator, but I still don't get it, desperation is making me posting here. The problem comes as The problem then continues with other questions but I'm having troubles with the very first one...

This will probably end up being a stupid question with a simple answer, but if you don't ask and just accept things then where's the understanding? Anyway, the spectrum of emission is usually shown as some form of Intensity vs Wavelength, my question is how does it relate to time and how is it...

Can someone please tell me the basics to how a cystal radio works? And also what are all the components that makes up a crystal radio? Thank you!

[SIZE="4"]Definition/Summary Stress is force per area, and is a tensor. It is measured in pascals (Pa), with dimensions of mass per length per time squared (ML^{-1}T^{-2}). By comparison, load is force per length, and strain is a dimensionless ratio, stressed length per original length...

I'm a non-electrical engineering student however want to gain knowledge and experience with different electrical programming systems. I'm confused however as to all the different components and their differences. For example, why/when would you choose a PLC over an Arduino board or do these two...

Homework Statement Hello guys, I have to solve one basic problem, but I got the result twice smaller that it should be. So, I am thinking that I must have missed something basic. The problem is f\left(x\right) = 2x-1 for ##0<x<1##. I have to find the Fourier coefficients. I have found A_n...

The Little Rocket That Could [Figure 1. Check this out.] This post illustrates an example of KSP rocket design. The following are the rocket's design goals: Get three kerbals and a bunch of science items to the Mun, in an Apollo style mission: such that two kerbals (and science) land on the...

So, usually I like to give a long description of how/why I am asking such a question, but I think this time, I'll be quick and to the point. Truth is when I first came to this site, I think I started asking questions that were well beyond my current knowledge, so I would like to take the time...

Homework Statement Hello I'm trying to self study A First Course in General Relativity (2E) by Schutz and I've come across a problem that I need some advice on. Here it is: Use the identity Tμ\nu,\nu=0 to prove the following results for a bounded system (ie. a system for which Tμ\nu=0...

So I have been interested in learning about electronics for a while but I can only find good reading sources for learning. I have a load of trouble learning from reading and I best learn from things like experimentation or being taught. I would like to experiment but at the same time I don't...

While trying to learn kalman filters, I see contradictory info for a simple gyro State Space representation. Please be patient with this post, I've put a fair bit of time trying to make it easy to follow and read! My goal is to understand how a moving IMU's orientation can be found. I'd...

Hello! In my studying of work I've always been told that work done (by what? ) = Force (component along its path) times the distance it moves. Mathematically, W=F.s ... My question here is what is the geometrical presentation of saying Force x Distance ... In other words, when we multiply...

The mass is released at height h above the spring, how far will the spring move? Ei=mgh,Ef=kx2/2+mgx...why the second equation isn't Ef=kx2/2−mgx? Since it is below the "zero".

I'm trying to get get a good base for learning further mathematics. Would an intro abstract algebra, analysis, and category theory text be good places to start? There are so many different places you could start and I'd like to first learn about those areas of math which help most when learning...

Hello I am having difficulty in comprehending the basics of fluid mechanics . I have few questions which I would like to put one at a time , so as not to create any confusion . In the following attachment , a container with a liquid rests on a surface .I would like to understand what are...

Hello, I have a theoretical question, I am struggling to understand the meaning of differential. I know the formula, I read it all in the calculus textbook. I don't understand what is the meaning, maybe geometric interpretation and use. In addition, I don't understand the difference between dz...

Before I begin, I apologize for any bad English, it isn't my first language. I'm a medical student who didn't do any mathematics for 3 years. However, after finding out the "plug 'n chug" approach isn't really what mathematics is about, I became interested in learning it from the basics all...

I feel retarded because I'm not understanding this equation despite getting A's in all my math classes. i(t) = \frac{dq(t)}{dt} some how becomes q(t) = \int^{t}_{t_{0}} i(t)dt + q(t_{0}) I'm guessing we apply the integral operator \int dt to both sides. so where is the q(t_{0}) term on...

Homework Statement The question in short: If the resultant force acting on the bracket is 750N along the x positive axis, what is the magnitude of F and the direction (theta) The Attempt at a Solution I have tried for several hours now trying to get this done. I have made a table for...

We don't have rigorous approach to statistical mechanics but have an intuitive one.We follow Concepts of Modern Physics by Sir Arthur Beiser. It is given that n(ε)=g(ε)f(ε) Here ε is the energy state. where according to my understanding n(ε)=number of particles which are present in an...

what is fermi energy?

Homework Statement This problem has analogies in the game of pool. Puck 1 slides on a horizontal, frictionless surface with velocity v and collides elastically with stationary puck 2; each puck has the same mass, m. The pucks move off with velocities v1 and v2, as shown. The angles θ1 and θ2...

which books are best for learning whole stuff about QM(also advanced)?anybody refer me?

In the Millikan oil drop experiment, was the oil particles positively or negatively charged. and what were the charges of the plates. My textbook and what my gr.10 notes say is that the oil droplets and the bottom plate were positive, but every source online says that they were negative and that...

Hi guys! I've got 2 extremely simple questions, hence a single thread. First, I want to know whether the conservation of the 4-momentum in a closed system implies the conservation of the energy and of the 3-momentum. Let's assume we consider 2 different times, ##t_i## and ##t_f##. Then...

Electric Circuits and Gadgets -- Basics Please Well, when I lived in India, I remembered a neighbor whose occupation was creating little gadgets, such as watches, lasers, etc. I am now living in Pakistan, and missed the chance of asking the guy how he learned what he knew. I am curious to...

Why does node analysis have a ground node?

Hi all, I have recently started my machine design course in engineering and I am finding the topic of bearings difficult to follow. I understand the need for bearing.What I cannot understand is what axial,radial and tangential loads will try to do with the bearing (especially the tangential...

If you want, see how this would work as really beginner-level introduction. I'm hearing misconceptions about expansion---not necessarily from the present company, more generally in lay public. People ask what is expanding? how can galaxies recede faster than light? if space is boundaryless then...

I would appreciate some advice from "old hand" heat exchanger guys regarding "good design practice" on approach temperature for tube and shell . Here's what's up: A friend works in a solar plant. Oil is heated in parabolic reflectors and used to preheat feedwater for a traditional...

I am just introduced to basics of superconductivity in Engineering Physics. My lecturer asked a question: Is the resistance of a superconductor zero or close to zero? And my answer was close to zero. I have read that the resistance of a superconductor is exactly zero, but then when I put some...

I would like some help in understanding the basics of a blast caused by an explosion. The company I work for supply instrumentation systems which are then connected to accelerometers to measure shock and air blast sensors to measure the pressure wave caused by any ballistic blast. I would like...

I missed my class that introduced us to moment generating functions, and my notes are missing some pretty essential parts to helping me understand them, so here it is: Homework Statement Find the moment generating function of f_X(x)=e^{-x}, x>0 Homework Equations...

well i am a starter in QM, i have 2 big doubts ! let me first tell what i understood , there is phsi which defines a state of a system, phsi times x is a position operator and phsi 's derivative of x multiplied by i h is its momentum operator ... well then i operator these in phsi and what do...

I'm an M.E. and I want to learn about electronics to the point where I can design and build circuits that do what I want. Right now I have only a very basic background from undergrad EE courses, I know a bit about opamps and transistors and diodes and transformers and the E&M physics theory and...

good afternoon i want to learn the following topics in the lucid way: eigen value,eigen function and related problems of particle in a box, harmonic oscillator,tunneling through barrier,wave function in cordinate and momentum representation,commutators

Hi, I am interested in purchasing a telescope, although I am not very familiar with the parts and overall structure. introductory feedback, and recommendations would be much appreciated, and also I don't want a budget of $500 (preferably price range $350-$450).

I am trying to follow examples solved by the publisher of my book in order to understand the problem. However, I can't understand why he is solving it like this. What is confusing me, is why v1=(12+8)*1/8 why is v1 not 12*(1/8). Why is he adding the 8ohm resistor in there? Any help would be...

how are cdf and pdf related in statistics? please help i have a test tomorrow

I'm hoping for verification here that I'm not crazy on some very very basic chemistry questions. I've worked 7 problems on a practice test (the real thing is next Tuesday). Only 2 of my answers agree with the answer key. Here are the most dramatic examples. Please tell me I'm not crazy...

I am going to major in chemical engineering next year, but I feel like I don't have a great base in math, chemistry, or physics. Sure, I got "good" grades at the time, but I took a year off the subjects and now I feel like I am helpless. What would be the best way to go about learning this on...

I am a young student striving to learn more about science. I'm quite a nerd, I study all day long and I'm matriculating this year at the age of 16... I've chosen to study more into Quantum Chemistry and I need a book!

I was trying to study the inductor role in Flyback converters and all, they seem to rely on the principle that the inductor is first energized while the switch is closed and then, it acts as a voltage source itself when the switch is opened. All that is good, but I am confused with the...

I am idly curious about induction heating; specifically for heating 80L-100L of water from 20C to 100C as efficiently as possible with an emphasis on as little waste heat going to the surrounding environment as possible. I have done some precursory reading (...

The other day one of our power labs we were using rather large inductors; that is, approximately 10"x4" in the shape of a doughnut. There were 4 connections into the inductor. We connected a wire from one to the other, and then used the other two connections as any other inductor. Does that...