Relationship Definition and 999 Threads

Hi all, I have in mind that an engineering project tends to be quite "integrated", as in, it envolves different engineers. So, for instance, in order to build an aircraft, you need not only a mechanical engineer, but also an EE, Materials, managers, etc etc. So lots of teamwork. However, I'd...

I know that in a closed parcel of air, if we increase temperature then pressure rises and density remains constant If we warm a parcel of air that is open i.e not enclosed, such as the atmosphere. What happens to pressure? do we say it increases or decreases? The book I have states; If the...

Hello, I've noticed that some professors will jump between second quantized creation/annihilation operators and wavefunctions rather easily. For instance \Psi_k \propto c_k + ac_k^{\dagger} with "a" some constant (complex possibly). I'm fairly familiar with the second quantized notation, and...

What is the relationship between negative energy, negative mass and antiparticles? I have read some articles but I am still confused. Does negative mass exist? Does negative energy exist with the exception of the Kasimir effect which I understand. Are antiparticles really only the negatice...

Hello, I can not understand that a motor (pumping) requires a current of 63 A under a voltage of 390 vac, and requires a current of 72 A under a voltage of 365 vac. Normally when the voltage increases the current increases with (ohm law). Is that the power delivered by the engine which is 37 kw...

Hello PhysicsForum, There is something I don't get at the end of this course notes PDF file. In the last section, titled "Comoving distance and redshift", which I have copied below, we have a short derivation of the comoving distance and redshift relation. Almost all is well, the only thing...

< Mentor Note -- two threads merged and new user reminded not to multiple-post threads at the PF > i'm experimenting about refractive index and i can't figure out the relationship between concentration of the solution and Refractive index. What i found about this is that RI is connected to...

This is just a question that has been bothering me. I am not a student of physics, which is probably clear from my question. Hope it at least makes sense: You have a windmill with no friction. The wind is blowing at a constant speed causing the windmill to spin at 100 RPM.(a) The windmill...

I'm just looking for conceptual clarification re: the relationship between matter density and the Hubble parameter in the Friedmann equation. Just for quick reference, the equation I'm looking at is H2 = 8πGρ/3 - ka-2 (I'm working through Liddle's Intro text, and for now we're ignoring the...

In trying to understand the relationship between Higgs particles and gravitons, I would like to pose a question on hypothetical question: What would happen if you increase the Higgs field around a planet? It seems it would mean its mass increases, which would mean its gravitation increases...

Homework Statement For an engineering assessment (first year with no electrical background), we are using a solar panel to power an element for a distillation system. we have calculated our heat energy output requirement that we need from our heating element as being 800 J/s. For simplicity we...

Homework Statement The Higher Heating Value (HHV) of gaseous propane is given as 2220.0 kJ/mol. What is the value of the Lower Heating Value (LHV) of gaseous propane? Data for water (all in kJ/mol): H(g, 25 deg. C) = 45.85 ; H(g, 100 deg. C) = 48.17 ; H(l, 25 deg. C) = 1.886 ; H(l, 100 deg. C)...

Why the mass of disc does not changes according to Einstein's equation(e=mc^2) when we insert it inside a disc player and it shows us energy in the form of video on a tv/monitor screen. I think there's something wrong in this question, can anybody point out the error with reasoning.

I am currently enrolled in a statistics course, and the following is stated in my course book with no attempt at an explanation: Suppose that f is the probability density function for the random variable (X,Y), and that F is the distribution function. Then, f_{X,Y}(x,y)=\frac{\partial^{2}...

Homework Statement Given the transfer function: Find the phase relationship between the input and output voltage at high frequencies Homework Equations NA The Attempt at a Solution My approach was to find the phase of the transfer function, which I got to be: I assumed that "very high...

Then it goes on explaining how Gauss law would fail because for a very large surface, E field would be vanish with flux through it and though we can calculate div for this field it won't depend on source density. But I don't get what makes this particular function so evil that it would break...

Homework Statement Find the general solution to the equation: ##{u}\times{(i+4j)}=3k## Homework Equations ##u=(ai+bj+ck)## The Attempt at a Solution I am having trouble visualising what to do here. So my throught so far is that, if i do ##(ai+bj+ck)\times {(i+4j)}=(0i-0j+(4a-b)k) ## now if I...

More thermal conductivity means there's more energy?...

Hello, I did a calculation to determine whether a liquid with a fixed volume ##V##, would be spread over a larger surface area ##A## on the inside mantle of a cylinder, if the cylinder has a larger radius ##r##. So I’d like to find a relationship between the radius ##r## and the area ##A## over...

Can someone explain the terms viscoelasticity, creep and strain and their relationship to each other? Especially the difference between creep and strain. Any help would be greatly appreciated, thank you!

Hi, The Circuit I am referring to is a simple series circuit with the resistance of the wire is negligible. I am confused about the fact that if we increase the resistance of a resistor in a circuit, the PD across the component will also increase. From my understanding I thought increasing the...

Homework Statement If the amplitude of a weakly damped oscillator decreased to 1/e of its initial value after n periods, show that the frequency of the oscillator must be approximately [1 − (8π2n2)-1] times the frequency of an undamped oscillator with the same natural frequency. Homework...

Hello, quick question here I am studying mathematical astronomy / the history of , and I have noted that by raising the average sidereal period of any planet in our solar system, to the power .666666, that you are left with the average distance of that planet from the Sun, in AU I was told...

Hey guys, Can the use of mathematics even describe or determines the real world? I mean, mathematical physicists always used and rely on math equations to abstract math "entities" like quantum field, virtual particles, quarks, gluons, etc. Can a physicist used math to determine the existence...

Homework Statement Imagine a thin tower 4000 miles tall; ı.e. as tall as the earth’s own radius Re, placed at the north pole of the earth. Suppose you start at rest at the base of the tower and climb to the top (wearing a spacesuit and carrying supplies you need, so that your total mass is M)...

If air resistance increases with velocity, then if a ball is thrown upwards, does air resistance decrease as the upward velocity of the ball decreases or does it only increase and remains constant when the upward velocity of the ball decreases?

Why is the M-sigma relationship so tight, but the M-M_bulge relationship much looser? Don't the theories that black hole growth and star formation are coupled only explain why M_BH would be correlated with M_bulge? We might expect sigma to follow to an extent due to the stars having roughly...

What is nucleation and how it works? In cosmology, which is the relationship that nucleation have with quantum tunneling, vacuums and Big Bang?

Homework Statement An AC source was connected to a capacitor and an inductor (ignoring its ohmic resistance) in series. If the inductive reactance was equal to twice the capacitive reactance, and then the frequency duplicated, determine: 1. the relationship between the the current before and...

As gravity increases time slows, hypothetically if you were at a point with extremely low gravity would time run any faster?

Okay here's the question: If you sell widgets for 2 dollars, you sell 300 per day. If you sell them for 4 dollars, you sell 200 per day. assume linear relat., between price (x) and # widgets sold per day (y), write linear equation relating x and y I'm thinking I plot the x,y pairs, then...

im doing some personal research into building my own generator. i am looking for info on how wire diameter affects the power produced by the generator. specificaly: what AWG of wire is best for coils that are being used to generate as clost to the statdard killowatt/hour as possible.

Homework Statement See image below. Homework Equations motional emf = induced voltage = B L v The Attempt at a Solution I thought the answer would be A since there's a direct relationship between EMF and magnetic field strength. The answer is D.

Homework Statement I am currently trying to find a way to determine the relationship between launch height and range for a projectile launched at less than horizontal. Would vary launch height to and measure range. I need a directly proportional equation or at least a linear relationship...

What is relationship between discharge coefficient and minor loss coefficient. Am I right with that equations? hl – minor head loss k – minor loss coefficient ρ – air density A – pipe cross section area Cd – discharge coefficient Δp – pressure drop u – air velocity m – mass flow here is...

I'm currently studying wavelength and frequency and I've learned about the equation v= f*Lambda. What will happen if temperature is changed? I know that speed of the sound will increase. Does it mean that wavelength will also increase? I was curious because if temp. increases, the frequency...

Hy, If we double the voltage than what will be double A. power B. Current C. Resistance D. Both a & b

Homework Statement I am a rookie to the QFT extension in Mathematica called FeynCalc, and tried to use that into solving some quiz. Soon I met a problem upon some condition presented in a problem which declares an relation of two same tensor with different indices results in some value when...

Homework Statement Example 5.3 from The Marion Thornton book (fifth edition) of Classical Dynamics states the following problem: Consider a thin uniform circular ring of radius a and mass M. A mass m is placed in the plane of the ring. Find a position of equilibrium and determine whether it...

how demonstrate the formula ? the relationship between Force and Voltage and Torque? how to prove that this formula? << e-mail address deleted by Mentor >>

Homework Statement Prove that ##TdS = C_vdT + \alpha T / \kappa dV## Homework Equations ##T dS = dU - pdV## ##\alpha = \frac{1}{v}\left(\frac{\partial v}{\partial T}\right )_P## ##\kappa = -\frac{1}{v}\left(\frac{\partial v}{\partial P}\right)_T## The Attempt at a Solution The ##C_vdT## part...

Homework Statement Why is the following set of electric and magnetic fields invalid? ##E(x, y, z, t)= E_0 \sin{(kz-wt)} \hat{i}## ##B(x, y, z, t) = B_0 \sin{(kz+wt)} \hat{j}##Homework EquationsThe Attempt at a Solution So, I understand that either both should have (kz-wt) or both should have...

Q.1 Will time for an object be slowed ONLY when it travels VERY NEAR TO the speed of light? Or should it be EXACTLY in speed of light?

Cv = (∂U/∂T)v = T(∂S/∂T)v I can prove this by using the Maxwell relations, but I have trouble deriving it from the first law. dU = TdS - pdV (∂U/∂T)v = T(∂S/∂T)v + ∂S(∂T/∂T)v = T(∂S/∂T)v + ∂S Is there a problem with my derivation?

Homework Statement Coherent electromagnetic radiation is sent through a slit of width 0.01 mm. For which of the following wavelengths will there be no points in the diffraction pattern where the intensity is zero? A. Blue light of wavelength ##\lambda=500 nm## B. Infrared light of wavelength...

Hello I am interested in the Frenet-Serret Formulas (theory of curves?) relationship to theory of surfaces. 1) Can one arrive to the Frenet-Serret Formulas starting from the theory of surfaces? Any advice on where to begin? 2) For a surface that contain a space curve: if the unit tangent...

http://www.physicspages.com/2014/08/22/electromagnetic-waves-in-vacuum/ Sorry i have no idea how to get the last step in the vector form how to convert and mix it?thank you

I need 250 m/s of airflow speed in a wind tunnel. I can assume for this purpose, the test section of the wind tunnel has uniform flow. However, the wind tunnel can only generate a flow rate of 100 m/s but the pressure can be increased. I am drawing a blank on how could a generic boundary layer...

Hi, I got admitted into a graduate program in physics. My prospective supervisor pulled through my application and got me admitted. I was asked later by my supervisor which other programs I got admitted into? Is this a common question for a supervisor to ask?

Can someone explain why the GPS on my phone is improved when Bluetooth is on?