Approach Definition and 565 Threads

Studying QFT on curved spacetimes I've found the algebraic approach, based on ##\ast##-algebras. In that setting, a quantum system has one associated ##\ast##-algebra ##\mathscr{A}## generated by its observables. Here we have the algebraic states. These are defined as linear functionals...

Homework Statement 14.102 A comet at its closest approach is 125 x 106 km from the center of the sun (between the orbits of the Earth and Venus), where its speed is 45.5 km/s. (a) Show that the comet has an elliptical orbit around the sun. (b) Determine the period of the orbit in years (1 year...

[Moderator's note: spin off from previous thread.] Have you read Ohanian? He uses an entirely different approach much more in line with the Standard model type of equations and Lagrangian's, and shows how - first you get from an analogy with EM the linearised gravitational equations then how...

$\textsf{Two locomotives approach each other on parallel tracks.}\\$ $\textsf{Each has a speed of 155 km/h with respect to the ground.}\\ $ $\textsf{If they are initially 8.5 km apart}\\$ $\textsf{a. how long will it be before they reach each other?}\\$ \begin{align*}\displaystyle...

This is an IB problem from November 2017. Two rockets are separated by 6E8m (2 sec x c, or two light-seconds), w.r.t. Earth, and are approaching Earth from opposite directions. Rocket A approaches from left at 0.6c. Rocket B approaches form right at 0.4c. According to Earth, when do they...

Homework Statement The stream function Ψ(x,y) = Asin(πnx)*sin(πmy) where m and n are consitive integers and A is a constant, describes circular flow in the region R = {(x,y): 0≤x≤1, 0≤y≤1 }. Graph several streamlines with A=10 and m=n=1 and describe the flow. Explain why the flow is confined to...

Homework Statement Two cars approach each other on a straight road. Car A is moving at 16m/s and car B at 8m/s. When they are 45m apart both drivers apply their brakes. Car A slows down at a rate of 2m/s^2 while car B slows down at 4m/s^2. Where and when do the cars collide? Homework Equations...

I wonder how an object, like our sun, can approach a more perfect blackbody. We know that by the wiki definition, blackbody is something that absorb all radiation and is in thermal equilibrium. Its spectrum only depends on T. We also know that, our Sun's spectrum is blackbody like, while a...

Homework Statement A screenshot of the problem: imgur link: https://i.imgur.com/ljtoclm.png Homework EquationsThe Attempt at a Solution My first attempt at the solution was this: imgur link: https://i.imgur.com/TJcvOzy.jpg However, I have access to the worked solution, and it is...

Hello, I am dealing with a function f(x) involving various complicated trig functions. I took the first derivative of the function f(x), which is doable, and set it to zero to find the at which value x the function f(x) would be maximum. However, once I have the derivative of f(x), it does not...

Homework Statement Homework Equations friction force = F_v m=m1 The Attempt at a Solution is method 1 correct? if so, why method 2 came out with a totally incorrect answer. I understand that you can also set up acceleration equations for m1 and m2, since their acceleration are equal, and...

Homework Statement A bicycle of mass m is traveling at constant speed v around a curve of radius r without slipping. You can take the acceleration due to gravity as g. Calculate the angle of tilt, θ, that will enable it to balance. Homework Equations R=mg Rsintheeta (Length)=Fcostheeta...

I looked at the other threads that have discussed retrocausality, but a scan of the article https://phys.org/news/2017-07-physicists-retrocausal-quantum-theory-future.html?google_editors_picks=true seems to take a new approach. The paper also gives two references. Proceedings of The Royal...

Homework Statement A ball is dropped from somewhere above a window that is 2.00 m in height. As it falls, it is visible to a person looking through the window for 200 ms as it passes by the 2.00 m height of the window. From what height above the top of the window was the ball dropped? Is...

Hello, I have metrology in my 4 semester in Bachelor's of Engineering in Mechanical Engineering. However, the books that we get (Engineering Metrology, R.K Jain,) give only a brief principle of how the instruments work. I want to further my study of this subject with an intention to design...

Suppose i have an equilateral triangle and i want to find the principal axes of rotation passing through one of the vertex. How can i do that? I am thinking along the following lines but I'm not too sure: 1)Since the equilateral triangle has symmetry about a median, that definitely is one...

Hello everyone! I've been curious about this for a while and couldn't come to a conclusion on my own so I've decided to ask it here. I'm wondering if it's possible for a function, f(x), to have a rule which would allow it and it's derivative to both approach a constant value as x approaches...

In the context of General Relativity spacetime is a four-dimensional Lorentzian manifold M with metric tensor g, its Levi-Civita connection \nabla and a time orientation vector field T \in \Gamma(TM). In this context I've seem the following three definitions: A coordinate system is a chart...

In hydraulic lift utilising pascal law, larger piston area is A1 and the smaller piston area is A2 mass in = mass out and volume in = volume out (in-compressible),so A1*x1=A2*x2 (let x1 and x2 are displacements of respective pistons) A1*V1 =A2*V2 (on differentiation gives continuity...

Charles Link submitted a new PF Insights post Fabry-Perot and Michelson Interferometry: A Fundamental Approach Continue reading the Original PF Insights Post.

Hello all, I require your expertise on building an approach or a framework to identify and measure the jerk or vibration in a mechanical system with a slider. What I have is a slider (S) with a vertical link (L1) attached to it and another horizontal link (L2) attached at the tip of the link...

I was trying to finish the assignments of this link https://ocw.mit.edu/courses/electrical-engineering-and-computer-science/6-034-artificial-intelligence-fall-2010/assignments/MIT6_034F10_lab0.pdf unfortunately they are not numbered, but I dealt with the Tree reference one. In particular, given...

Hello. Suppose there are two objects that are traveling at the speed of light, and that the observer is in an inertial frame of reference. These two objects are say, a light-second apart, and are approaching each other. From the frame of the observer, each object covers half a light-second...

Homework Statement A cube of 8cm x 8cm x 8cm is divided into smaller cubes of 1cm x 1cm x 1cm and all the smaller cubes are numbered and arranged to form the larger cube. The smaller cubes are numbered such that the number on the cube represents the smallest volume enclosed by extending the...

What is the equation for a curve where x approaches infinity as y approaches infinity?

I have followed several derivations to obtain the formula for tunnelling probability in a finite square potential well. the standard result that is actually an approximation to a more complex result is; I get the derivation of this result shown in many standard texts. what I do not get is...

I have spent hours on the web and in libraries to obtain a general and careful approach to the notion of capacitance, without success. Please, read carefully the question: I already know the usual blabla about capacitance. Also, I appologize in advance for the length of this question. I...

is there a directly knowing the moment if the moment of inertia would be lower for an object? I am emphasizing on knowing the value of the constant value. For a sphere is 2/5 and for a cylinder 1/2, this constant values will be placed at c of cMR^2 without directly going into calculus. A...

Super moon Monday 11/14/16 . Full moon's closest approach in 70 years.

Homework Statement A swimmer jumps into a 5.1 km river and swims straight to the other side at 0.87 km/h [N]. There is a current in the river of 2.0 km/h [W] a)How long does it take the swimmer to reach the other side? b)How far downstream has the current moved her by the time she reaches the...

I feel like my approach to mathematics is strange, sometimes I just think about memorizing something when I see something new. I feel like memorizing something is the fastest way to learn because once you memorize it the logic seems to reveal itself. I'm trying to learn trigonometric...

Homework Statement Homework Equations C = q / voltage The Attempt at a Solution OK. [/B] By Kirchoff's Voltage Law, we have: EMF - ( q / Capacitance)x - (q/Capacitance)y = 0 Now. I know that having the dielectric increases the capacitance of X, so the voltage drop across it is smaller...

Homework Statement [/B] My problem is in figuring out how to solve number 22 through 23, particularly getting the set-up done. Homework Equations Newton's law of gravitation and coulomb's law of accelerationThe Attempt at a Solution [/B] I initially misread the question and thought that...

Homework Statement Determine the output voltage Vo(t) in terms of Vs Homework EquationsThe Attempt at a Solution If I were to use Nodal Analysis to solve this, would these be the proper nodal equations?\frac{V1}{-j1.6} + \frac{V1-Vs}{175} = 0 \frac{V_{I2}-Vo}{10k} + \frac{V_{I2}}{1k} = 0

Suppose there are a number of objects on top of each other and the bottom one being on top of a frictionless surface. The masses of all of them are given. The coefficients of friction between all surfaces of contact are given. And, the forces acting on each block are given (It's not necessary...

The sun's rotational period is 25 days at the equator. Given that the radius of the sun is 700,000 km, calculate the max velocity of approach or recession of the Sun's equator as viewed from Earth. Find the max change in wavelength of a spectral line due to the rotation and express it as a...

Homework Statement Homework Equations I know that U = q * V, so my attempted approach will rely on that method The Attempt at a Solution I was wondering if people could help me solve the problem and help me figure out why B is the correct answer and what the pitfall in my problem solving...

Hi everyone. I am told to find the equation of the tangent plane to the surface x^2 + 2xy^2 -3z^3 = 6. I do not know how to approach this problem, and I was wondering if anyone would be kind enough to help. I know that for example if I had an equation z = x^2 + y^2, with a point P(x0,y0) and...

I think I am missing something painfully obvious, but what exactly is the difference in algorithms used to solve PDEs vs ODEs? For example, I've been looking at finite difference methods and the general steps (from what I've seen, although particular approaches may vary) used to numerically...

Homework Statement Hi, I am studying gauss's law via this book below.[/B] http://faculty.polytechnic.org/cfletcher/Phys%20With%20Calc_Vol_2_web_pdfs_2010/i-Ch14-PCALC--GAUSS'S%20LAW.pdf On page 8, and 9, the book describes the shell method of finding the volume of the sphere and then using...

Homework Statement An object is in uniform circular horizontal motion at the end of a chord of length L. Its tangential speed is v. The chord is pulled into length 0.5L in such a way that the tension in the chord remains constant. As a result, the tangential speed: a) remains constant b)...

With basic fractions, the limits of 1/x as x approaches infinity or zero is easily determine: For example, \begin{equation} \lim_{x\to\infty} \frac{1}{x} = 0 \end{equation} \begin{equation} \lim_{x\to 0} \frac{1}{x} = \infty \end{equation} But, we with a operation like ##\frac{f(x)}{g(x)}##...

So far I have seen Sakurai, Townsend, Cohen Tannoudji, Feynman, and McIntyre. Are there any other books that take this approach? Just curious.

Hello everyone, I am a first year student taking electrical engineering and am looking for a systematic approach to doing these problems. If you guys (or gals) can offer any hints or tips to help me understand what this is, that would be great. Thanks

What do Physics Forums members regard as the best first introduction to differential forms ...?

Can anyone suggest a good text or a good online set of notes from which to make a first approach to the topic of differential forms ... ? Similarly a first approach to to tensors ... ? The thought is to use these notions in order to gain an understanding of differential geometry and ... later...

I saw a YouTube video presenting what seemed like a clever solution to ##x^{x^{x^{.^{.}}}} = 2## (which is to say: an infinite tower of exponents of x = 2). He said to consider just the exponents and ignore the base and realize that those exponents themselves become a restatement of the whole...

If there is a large mass near a black hole, is the event horizon teardrop shaped? Today I was thinking if it was possible to violate the idea that anything that passes the event horizon is gone forever. I forgot to label my picture, Figure 1 is the top and Figure 2 is the bottom. I imagine a...

Homework Statement imgur link: http://i.imgur.com/G9RKEH1.png Homework EquationsThe Attempt at a Solution [/B] Should I just consider that A and B are parallel with each voltage source respectively and so therefore that's the voltage drop that they experience individually? The ground...

There is charge ##q_0## which is fixed.from a distance far away another charge ##q_1## is fired towards it with speed ##V_0## then we know as both of these are positive charges these will repel each other as the charge ##q_1## comes closer. While coming closer to ##q_0##, it's speed decreases...