Constants Definition and 458 Threads

Hi. First off, sorry about the title, its not very descriptive but I had no clue on how to sum my question. I'm reading Sakurais' Modern Quantum Mechanics. In the discussion of the K operators (p47) he compares it to the classical momentum operator, states that K = p/(some constant) , and...

Has there been a debate as to whether fundamental constants can be chosen freely for a theory or some constraints make it unlikely that to be the case. for example the dimentionful parameters don't have a specific value, only combinations give FSC, that means(to my mind) that there is unlikely...

Am am presented with the problem: $$ h(t) = c - (d - 4t)^2 $$ At time t = 0, a ball was thrown upward from an initial height of 6 feet. Until the ball hit the ground, its height, in feet, after $$t$$ seconds was given by the function $$h$$ above, in which $$c$$ and $$d$$ are positive constants...

After two time constants of time have elapsed, the current in the circuit is how many times the final current?

Homework Statement I have got this circuit: I have to find coefficients k1 and k2, and time constants T1 and T2. Actually, we can see that T1 =R1*C1 and T2=R2*C2, but is it possible in this circuit or it's just theoretically time constants? I'm not sure, but as there is no amplifier in...

hello, I'm not a physicist, just a goofy gent with some far fetched ideas is it safe to say that all the energy and matter in the universe has been constant since big bang? would it be ok to assume that all the time and information has also been constant since the big bang? Been...

Eliminate the constants $y=c_1 e^{ax}cosbx +c_2e^{ax}sinbx$ since there's two constants I took the derivative twice $y'=c_1\left ( -e^{ax}b\sin{bx} + ae^{ax}\cos{bx}\right )+ c_2\left ( e^{ax}b\cos{bx} +ae^{ax}\sin{bx}\right )$ $y''=c_1\left [ \left (...

Homework Statement Let ##a>0## and y(x)=\left\{\begin{matrix} -x ;& x<-a\\ Cx^2+D;& -a<x<a\\ x;& x>a \end{matrix}\right. a) Find ##C## and ##D## so that ##y\in C^1(\mathbb{R})## b) For A>a calculate ##\int_{-A}^{A}(1-({y}')^2)dx## c) Is it possible to find ##C## and ##D## so that ##y\in...

So I have this question: And I just want to check my answer. Am I right? I think that the first formula is the theorem of integration so a and b are limits o integration and I'm not sure about the second formula, I think it's the anti derivative formula making that the anti derivative...

Homework Statement Let μ represent a positive constant. Find the derivatives of: (x^2)/(2μ) Please check work. I am confused about the "constant" part. Can't you just set μ = some positive number and find the derivative that way? Homework Equations (x^2)/(2μ) The Attempt at a Solution...

eliminate the arbitrary constant, 1. $\displaystyle y=mx+\frac{h}{m}$ h is a parameter, m to be eliminated.2. $cxy+c^2x+4=0$ eliminate c I don't know where to start please help me get started. thanks!

1. eliminate B and $\alpha$ from the relation $\displaystyle x=B cos(\omega+\alpha)$ in which $\omega$ is a parameter(not to be eliminated). I first took the two derivatives of x with respect to t: $\displaystyle \frac{dx}{dt}=-\omega B\sin(\omega+\alpha)$ $\displaystyle...

Homework Statement NaCl (a0 = 5.64A° ), NaBr (a0 = 5.98A° ) and KCl (a0 = 6.30A° ) all have the same structure, which is the NaCl structure. (a) Assuming the spacings are determined by the ionic radii of the relevant ions, what would value would you expect for the lattice constant of...

Homework Statement A 10V supple is connected to a 2.2μF capacitor in series with a 10kΩ resistor. To what value will it have charged after three time constants? Homework Equations I know that T=RC but I have no idea beyond this point The Attempt at a Solution T=RC T=2.2μF*10kΩ...

So I was revising elementary classical physics and Newton's equations of motion. When you apply a force on an object in free space, far from gravitational fields, you find that the object accelerates. By conducting experiments where you vary the force or the mass and look at the acceleration...

When normalising the S.E. in spherical coordinates you split it up into 3 integrals, with respect to r, theta and phi. My question is, once you have found the constants for each, when writing out the normalised PSI do you simply place them as a product in the solution? i..e PSI...

How would it make any sense to use dimensionless numbers to represent physical things? From wikipedia: If you are comparing the strength of forces, and you are using these numbers to do so, I would have thought that these numbers would represent units of - well, force. Clearly I must...

Hello , so the question is basically like that , I did some thinking about evolution and so I came to this question. Now the universe today with it's proton size and mass and particle charges , gravitational constant and all other things we know and yet don't know about , seems kinda precise...

Homework Statement if a value has a variables that cancel out can it be considered a constant? looking to make an equation out of proportionality statements Homework Equations this is the equation that we are supposed to get: f=√((F)/(4∏2mr)) the 3 proportionality where f2=kF ...

OK, so for starters, I'm not asking anyone to re-post results found in other books, papers, etc. That'd be entirely contrary to the basic idea of this 'ere thread. What I'm really interested in is this: have you - yes YOU, personally - found any new or presumably unique series acceleration...

Spring Constants and Conservation?? Homework Statement In the dangerous “sport” of bungee-jumping, a daring student jumps from a balloon with a specially designed elastic cord attached to his waist. The unstretched length of the cord is 22.2 m, the student weighs 326 N, and the balloon is...

Homework Statement This was an electrical engineering lab, dealing with the steady state response of an RLC circuit (diagram attached). The main part of the lab consisted of experimentally determining the circuit's critical resistance value, and viewing the overdamped and underdamped...

I am studying QFT and got stuck on one question which may be simple. Why is structure constants (in Lie algebra) real and independent on representations? Can you give me a detailed proof? Thanks!

I'm reading Peter Woit book "Not Even Wrong" and have been contemplating on the constants of nature or the parameters. I have some questions. 1. Which of the Constants of Nature do you think can be calculated by principles? Should they in principle be calculable? 2. Should a Unified...

The given family of functions is the general solution of the D.E. on the indicated interval. Find a member of the family that is a solution of the initial-value problem. y=c_1x+c_2x\ln{x} on (0, \infty) and x^2y''-xy'+y=0 and y(1)=3, y'(1)=-1 So plugging in y(1)=3 gives 3=c_1+c_2\ln{1} and...

Homework Statement A force Fext(t)=F0[1-e(-a*t)] acts, for time t>0, on an oscillator which is at rest at x=0 at time 0. The mass is m; the spring constant is k; and the damping force id -b dx/dt. The parameters satisfy these relations: b=mq and k=4mq2 where q is a constant with units...

L \frac{di}{dt}+Ri=E and we're given i(0)=i_o I,R,E,i_o are constants. So I rewrite equation as \frac{di}{dt}+\frac{R}{L}i=\frac{E}{L} therefore P(i)=\frac{R}{L} let \mu(x)=e^{\int \frac{R}{L}dt}=e^{\frac{tr}{L}+C} multiply equation by integrating factor to get e^{\frac{tR}{L}}...

Hi, everyone. I once saw a science program with the danish astrophycisist Jens Martin Knudsen, who said that there exists seven absolutely fundamental constants of nature, and if one of these were changed ever so slightly, it would lead to drastic changes in the whole universe. So my...

Homework Statement The problem calls for finding the relationship between the constants A and B in the following equation of an instantaneous electric field: E=[A(x+y)\widehat{a}_{x}+B(x-y)\widehat{a}_{y}]cos(wt) The details of the medium in which the field exists are that it is...

Hello, I am reading Planck's Unit. What I understand is that what is the need for Planck's unit. Kilogram, meter and second are measurement, rather arbitrary measurement, which humans have done in the past. The question is what do we know that is constant throught the universe? We know (1)...

Homework Statement Wow LaTex fail... anyone know how i make this look like not ****? I had it looking all pretty on http://www.codecogs.com/latex/eqneditor.php and it gave me these codes as my latex markup but it didn't come out right... why do they look like source code and not the pretty...

I was thinking about units and started wondering about coupling constants. In unit-independent form, the fine-structure constant is defined as \alpha = \frac{k_e e^2}{\hbar c} I don't have a deep knowledge of particle physics but I know that there are weak and strong charges which enter the...

Differential Equations--Finding Constants Homework Statement I uploaded a pdf document, which contains the problem I am currently working on, namely, problem number 7Homework Equations The Attempt at a Solution I am having particular difficulty with this portion of the solution: "(ii) At y=3...

Homework Statement In Exercises 49 and 50, find values of a, b, and c(if possible) such that the system of linear equations has (a) a unique solution, (b) no solution, and (c) an infinite number of solutions. 49. x+y ~ = 2 ~y+z =2 x+ ~ z =2 ax + by + cz=0 Homework Equations...

It's fairly straight forward to find information on how to solve a system of equations like this: 2x + 3y + 4z = 1 3x + 4y + 3z = 2 4x + 5y + 3z = 3 It has numerical constants in front of each term. You could use Gaussian elimination and solve for one, infinite, or no solutions. (The above...

Homework Statement Evaluate ∫-x/(x+1) dxHomework Equations The Attempt at a Solution I do a U-sub u=x+1 du=dx x=u-1 -∫(u-1)/u du -∫[u/u - 1/u] du -∫1 - 1/u du -[∫1du - ∫1\u du] -[u - ln(u) + C] ln(u)-u+C ln(x+1)-(x+1)+C ln(x+1)-x-1+C I combine -1 and C into a single C to get the...

I am wondering ? is it possible that the constants that govern the laws of physics was different during other periods of our universe history ?

Homework Statement Calculate the energy for 1S->2P transition in lithium and carbon. We had to calculate the energy and eigenvalue equations (though I verified these are correct) Homework Equations E = mc^2/sqrt(1+(Za/lambda)^2) lambda = n + 1/2 + sqrt((l+1/2)^2- (Za)^2) The...

I understand that by uncertainty relations, it is possible use an EFT to a range of energy, forgotten the interactions for bigger energies. But, ¿ why change the values of coupling costants? And, ¿ how can tell that there is no intermediate particle that happens with low probability in...

Folks, I remember once seeing an equation that linked all the important fundamental constants - electron charge/alpha, gravitational constant, planks constant, speed of light, electron mass etc - in a dimensionless relationship. But for the life of me I cannot find it -google doesn't know...

Suppose you have a function y = f(x) such that the domain of f(x) is 1 ≤ x ≤ 6 and the range of f(x) is −3 ≤ y ≤ 5. a) Find constants B and C so that the domain of f(B(x − C)) is 8 ≤ x ≤ 9 B= C= b) Find constants A and D so that the range of Af(x) + D is 0 ≤ y ≤ 1 A= D= I'm working on...

How is the effective (or renormalized) coupling constant at a given momentum scale scale measured? If one wants a definition which makes it easy to measure I would think it would be natural to use the LSZ formula which connects the measurable Feynman amplitude with the amputated greens...

Homework Statement How many time constants must elapse if an initially charged capacitor is to discharge 55% of its stored energy through a resistor? Homework Equations The Attempt at a Solution I don't even know where to start, so please a nudge in the right direction would help...

Homework Statement gas impingement flux density is given by ∅=P/\sqrt{}2mkT where m- mass of a molecule show that ∅=3.513*1022P/\sqrt{}MT where pressure in torr and M-molar mass of molecule then ∅ in molecules per cm2 per second Homework Equations ∅=3.513*1022P/\sqrt{}MT...

Homework Statement Suppose for some unexplained reason you are skateboarding and wanted to use a spring to launch you off a ramp. Assuming you have a mass of 70 kg, if the spring has a spring constant k = 625N/m and is compresed 5m. 1.If the ramp has a 60° and is 10m long, will you make it...

Homework Statement For the circuit below, the switch has been closed for a period of time long enough for steady state conditions to have been reached. a: Determine the time constant before the switch is opened b: Determine the time constant after the switch is closed c: Determine the...

Homework Statement Find the units of k1, k2, k3, k4, and k5. Write rate reactions for dA/dt a. A\leftrightarrowB k1 (forward) k2 (backward) b. A + B \rightarrow C k3 (forward) c. A + R \rightarrow 2R k4 (forward) d. A \rightarrow B k5 (forward) Homework Equations...

Hi, How can I calculate such terms d^Aae d^ebD f^AaE f^EbD d^Aae d^EbD f^AaE f^ebD Cheers, Safinaz

Homework Statement yy''+(y')2 = 0 Homework Equations yv(dv/dy)+v2=0 The Attempt at a Solution Variable separable when solving for the first step the result is: - ln |v| = ln |y| + C1 Now, I've looked at the remainder of the solution with a few other sources and the cause of...

Homework Statement What are the cases in which constants of integration can and cannot absorb terms and operations and just be redefined as c. Homework Equations The Attempt at a Solution As long as I keep redefining my constant of integration I can say -c=k ac=k where...