Constant Definition and 1000 Threads

Why can we always drop any constant term in a Lagrangian density in quantum field theory? This issue is somehow related to the constant term being some kind of cosmological constant? Can you please explain this issue?

Homework Statement I wrote an exam today and a question worth quite a bit of points asked Determine the value of a capacitor in a series circuit that will give a time constant of 4.0 ms and is isn series with an inductance of 3mH Homework EquationsThe Attempt at a Solution I do not believe...

The pion decay constant f_{\pi} is defined by <0|\overline{d}\gamma^{0}\gamma^{5}u|\pi^{+}>=f_{\pi}m_{\pi} where I have set the momentum \boldsymbol{p}=0 (and used the temporal component of the axial vector). Now, at the right-hand-side the dimension is two (the decay constant and the mass are...

How does one find the normal force when the object is not at constant movement or at rest.

Homework Statement A uniform chain lies in a heap on a table. If one end is raised vertically with uniform velocity v, show that the upward force that mus be exerted on the end of the chain is equal to the weight of a length z + (v^2/g) of the chain, where z is the length that has been uncoiled...

Homework Statement Deep in space, there is a particle density, p, is 1.01cm^-3. Pressure is extremely low, P, is 5.1 x 10^-17 N/m^2. What is the average temperature of mostly empty space? Answer in K Homework Equations T=P/pKb The Attempt at a Solution I plugged in...

Chaos could appear in the system if there is some nonlinearity. My question is how to explain that there is no chaos in constant acceletating system s(t)=v_0t+\frac{at^2}{2} when equation is nonlinear? Why is important only that difference and differential equation be nonlinear. It confusing me.

This thing has been bugging me lately that can the constant mass density phenomenon of the universe may not be due to inflation? Can it be considered a consequence of the Casimir effect on the ( Supposed) boundaries of the universe?

Hi I'm in high school but what I'm going to ask you is probably being teached in college. General formula: p=(2/3)*(N/V)*Ek p- pressure N- amount of molecules V- volume of the container Ek - AVERAGE kinetic energy I've been told by my physics teacher, that 2/3 constant factor in kinetic theory...

Hi, I am learning ODE and I have some problems that confuse me. In the textbook I am reading, it explains that if we have a separable ODE: ##x'=h(t)g(x(t))## then ##x=k## is the only constant solution iff ##x## is a root of ##g##. Moreover, it says "all other non-constant solutions are separated...

dV/dx=E E*q=F=m*a dq/dt=I v/R=I Say you have a situation where you have a constant DC current in a conductor. Applying the above equations to this situations seems to lead to a contradiction, so I’m confused. -So if you have constant DC current then that indicates dq/dt is a constant -If dq/dt...

Homework Statement Two smooth planes are joined at one end so that they form a V shape. The join is such that a mass placed on one of the planes will slide smoothly down one side of the V and then move up the other side. Find the period of the motion (T) of such a mass in terms of x0 (the...

Homework Statement The separation between energies of an oxygen molecule is 2061 cm-1 (wavenumber). Treating the molecule as a simple harmonic oscillator whose fundamental frequency is related to its spring constant and reduced mass, calculate the spring constant for an O2 molecule. meff =...

Homework Statement Proving PV^gamma = constant In adiabatic expansion. Q = 0 Homework Equations N/A The Attempt at a Solution ΔEint = W nCvdT = PdV = nRT / V dV ∫Cv/T dT = ∫R/V dV Cv ln(T2/T1) = R ln(V2/V1) ln(T2/T1) = (R/Cv) ln(V2/V1) T2/T1 = (V2/V1)R⋅gamma / Cp P2V2 / P1V1 =...

How about proper length in curved spacetime? Let's consider the radial distance between two spherical shells in Schwarzschild spacetime. The proper distance between them follows from the spacelike form of the metric with ##dt=0## for simultaneity. So I think having the r-values of the shells the...

Homework Statement Find the general solution to the differential equation: Homework Equations Separation of variables for solving 1st order separable differential equation. The Attempt at a Solution Using separation of variables, I can write: My questions are: 1) Am I correct to...

Homework Statement When Voltage is oscillating (A/C), then in a simple circle with steady resistance, the current will be proportional to the voltage. When voltage increases, current will increase. And when voltage decreases, voltage will decrease. Is it also true that in a simple circuit...

Homework Statement A sample of iodine contains 1 atom of the radioactive isotope iodine 131 (131I) for every 5 * 107 atoms of the stable isotope iodine-127. Iodine has a proton number of 52 and the radioactive isotope decays into xenon 131 (131Xe) with the emission of a single negatively...

Homework Statement Homework Equations F=m*a ΣF=0 The Attempt at a Solution Firstly, I tried to work on the normal force of bowling ball. But I can't get the answer. I don't get the idea that bowling ball could be kept at constant height, I didn't really understand the question guess. Can...

Is the light constant (3*10^8 m/s) the maximum speed for a beam of light or its photons which travel in waves?

(Moderator note: moved from technical forums, so no template) Does anyone know how to answer this question? A 1 meter spring lies horizontally on a table. You hang it vertically being held by one of its ends. Because of the mass of the spring itself it now extends to 1.1 meter. You hang a...

Imagine that we wanted to build a slingshot, using one piece of rubber attached to two hooks - each on a side. We use a rubber, whose spring constant is k. My questions are: 1. If we began to string that slingshot and the rubber would begin to fold, what would happen with the string...

Homework Statement the trajectory γ: ℝ→ℝ3 of a charged particle moving in a uniform magnetic field satisfies the differential equation γ''= B x γ'(t) . where B = (B1, B2, B3) is a constant 3-vector describing the magnetic field, and × denotes the vector product. (a) Show that the particle...

Hey! I have a question and a drew up a diagram to help out. I drew up a circuit that includes just a voltage source and a resistor. I know the voltage is constant in each of the circled portions of the circuit. As in, as you move through the wiring, the voltage doesn't change from one point to...

Homework Statement A cockroach crawls with constant speed in a circular path of radius b on a phonograph turntable rotating with constant angular speed omega. The circle path is concentric with the center of the turntable. If the mass of the insect is m and the coefficient of static friction...

Guys,, please check my own way to get Drag coefficient and Terminal Velocity by given Drag force,.. okay,, lets for example: we know drag force is Fd= Cd*pf*v^2*A/2,, ill give little example (Cd=.02)*(pf=1027kg/m^3)*(v^2=.0025m/s)*(A=24m)/2 =( Fd .6162N) so drag force is .6162N,, okay..according...

Despite being a constant, It has both dimensions and a unit, can someone kindly explain why ?

Homework Statement The Spherical region a<r<b carries a charge per unit volume of $$\frac{A}{r}$$, where A is constant. At the center there is a point charge q. Find A such that the Electric field in a<r<b is constant. Homework Equations Law of superposition and $$E=\frac{kq}{r^2}$$ The...

I have read that Young's Modulus, like spring constant, is a measure of stiffness (how hard it is to deform a material). Though apparently, Young's Modulus is a way of doing so that applies only to the material and not its shape, where a spring constant value depends on the dimensions of the...

Homework Statement For a model of a proton's charge distribution, : [/B] I have to find the constant of normalisation for rho. Homework EquationsThe Attempt at a Solution [/B] I wrote p(r)=p_0 * (e^-r/R)/r I then wrote it as p_0^2 * integral from -infinity to +infinity of (e^-(r/)^2)/r^2 =...

Homework Statement I work as a supplemental instructor for an intro physics class. As I was preparing my worksheet for this week I came across this problem. A basketball player can jump to a height of 55cm. How far above the floor can he jump in an elevator that is descending at a constant...

Homework Statement A 747 Jumbo Jet must reach a speed of 290km/h by the end of the runway to lift off. The 15L-33R runway at Toronto International Airport is 2,770 meters long. The main Toronto Island Airport runway 08-26 is 1216 meters long. Assuming the jet has a constant acceleration, for...

Given: ##\textbf{E}=\hbar \textbf{k}## where ##\textbf{k} = [\vec{k}_1, \vec{k}_2,\vec{k}_3, i c \omega]## If ##\textbf{k}## can vary continuously, how does the equation imply that energy is quantized? For example, ##y = m x +b## where ##m = \hbar## does not imply quantized ##y##. For...

HOMEWORK POSTED IN WRONG FORUM, SO NO TEMPLATE I have encountered a problem at the university in which there is a thermally isolated container of constant volume in which the number of particles and temperature change with time(the temperature increases). The change in particle number ensures...

In 1-dimensions, the final orientation after undergoing constant angular acceleration is: \theta_f = \theta_0 + \omega_0 t + 0.5 \alpha t^2 What is an analogous equation in the 3D case? In other words, if I know the initial orientation (say, as a quaternion), angular velocity (as a 3-vector...

Hi there, I am currently studying charge transfer reactions between metallic electrodes and redox couples in aqueous electrolytes (in a diffusion limited system), and I was wondering about the influence of the rate constant on the reduction/oxidation peak maximum. Typically, it is assumed that...

Homework Statement Im trying to understand what would be the correct approach for calculating the constant pressure specific heat for an ideal gas undergoing a process where the temperature is changing. The reason I am asking is because the equation used to calculate Cp0 is dependent on the...

Considering special relativity, let us take an object accelerating at a rate of 6m/s^2. Let's say that this object is large enough for an observer to securely stand on it while it is accelerating. Would this object be able to accelerate at this rate forever without reaching the speed of light...

I have an example: Let us say you are on a large object with a mass of 5x10^10kg accelerating upwards at a constant velocity of 5m/s^-2, and there is a ball 0.1kg on top of that object. This ball should be accelerating at the same pace. The ball is then held up 5m from the surface of that...

Hello everyone, I have a very simple question but for some reason, I couldn't find the exact answer to it on the internet. Let's say we have a formula y = k/x where k is constant and x and y are variables. Assume that I am given the absolute uncertainty in x how should I calculate the...

Hi, I've been dsicussing this with som friends, and would be thankful if someone took the time to explain it to me :) The scenario: Car A travels at constant velocity (80km/h) along the road and hits a brick wall. Car B acellerates upward towards 100km/h, and at excactly the moment it passes...

Hi everyone, I am working on some problem relating to radars. The problem boils down to finding the frequency of the complex exponential in a constant + complex exponential + noise model. I found some papers on sinusoid recognition but they use the sinusoid + noise model only. I tried to come...

Homework Statement A lossless transmission line has an inductance of 9.0 nH / m and a capacitance of 3.6 pF / m. a) What is the line's characteristic impedance? b) Calculate the phase constant of a frequency of 1 GHz. Homework Equations Equation of characteristic impedance of a transmission...

1) If I vary charge densities, but keep current density constant, do I get any sort of electromagnetic wave? 2) If the answer to question 1 is no, then if I vary charge densities, but keep current density constant, could I conceivably have a two isolated "open circuit" current elements of...

Hello, I am finding this questions quite difficult, can someone please offer some insight as to what needs to be done. Do we need to do limit tests to the left and right of x = 7?

1. Question to problem A car moving with constant acceleration covered the distance between two points 57.9 m apart in 5.02 s. Its speed as it passes the second point was 14.4 m/s. (a) What was the speed at the first point? (b) What was the acceleration? (c) At what prior distance from the first...

I have never had to use the English Engineering System so I am having a bit of a struggle here. I understand the concept of an inconsistent system of units. I understand the following 2 statements: 1lbf = 1lbm x 32 ft/sec^2 1lbf = 1slug x 1 ft/sec^2 When given a problem that is asking for the...

Homework Statement A = 20 cm Given the graph, what is the phase constant(in degrees)? (I have already solved for amplitude and frequency) Homework Equations x(t) = A cos (wt + ϕ) The Attempt at a Solution x(t) = A cos (wt + ϕ) Taking from t = 0, we find: 10 = 20cos(w*0 + ϕ) 10 = 20cos(ϕ) 1/2...

Hello... Can the cosmological constant become so rigid as to resist the 120 magnitude quantum contribution? Where is the mathematical terms for it in GR EFEs? is the effect like contraction instead of expansion? Because the 120 magnitude quantum contribution should immediately warp spacetime...

Compute a Lipschitz constant K as in (3.7) $$f(t, y_2)-f(t, y_1)=K(y_2-y_1) \space\space (3.7)$$, and then show that the function f satisfies the Lipschitz condition in the region indicated: $$f(t, y)=p(t)\cos{y}+q(t)\sin{y},\space {(t, y) | \space |t|\leq 100, |y|<\infty}$$ where p,q are...