Reference Definition and 1000 Threads

I tried asking a similar question in cosmology but got no answer there so here goes... Suppose I am on a windowless spacecraft in the middle of an intergalactic void. I know that the spacecraft is spinning from measuring the centrifugal forces but have no way of observing the outside...

I don't have too much of a clue of how to begin the problem. I first wrote the angular moementum of the system of particles: →M=∑mi(→ri×→vi)M→=∑mi(r→i×v→i). Then I know that the angular momentum from of the moving reference frame would have the velocity as the sum of the velocity of the frame...

I am currently studying quantum synchronization. I am reviewing a https://www.researchgate.net/publication/251232415_Quantum_Synchronization_of_Two_Ensembles_of_Atoms which describes quantum synchronization of two ensembles in a cavity. As such, I have a query regarding a cavity physics related...

I have lately been working with Numerical Analysis and I am using Finite Difference Methods for Ordinary and Partial Differential Equations by Randall J. LeVeque. It was recommended to me by a friend of mine (physicist) https://epubs.siam.org/doi/book/10.1137/1.9780898717839?mobileUi=0&...

Back in the day, when Perl was my go to language, Programming Perl, the Camel Book, from O'Reilly was The Reference. It was the quick and concise way to get an answer. And you'd probably learn something you weren't necessarily looking for and get a chuckle along the way. Now that Python is my...

Hello Is it even possible to have an answer for D given condition #4 ? i need help in just for question D, and not everything else . Thanks :] The Attempt at a Solution Because Either S or S' Could be accelerating, and depending on which one and how much is accelerating, there will be different...

Hi everyone. Please be gentle with me, I am not a physicist! I am a layperson with an interest in learning more, and I’m reading a book called ‘How to Teach Relativity to Your Dog’ by Chad Orzel. It’s supposed to be physics for dummies, but it’s clearly not dumbed down enough for me because...

Hi. If 2 bodies with charge q are in rest then both have electric force ##F_1=\frac{q*q*k_q}{|\vec{r}|^2}##. But in another frame of reference, that is moving with velocity v relative to first frame of reference, they feel both magnetic and electric force...

Can light photons be considered as a privileged inertial frame?

Peeling this out into its own thread for clarity: How is time dilation of extreme reference frames (photons, black holes, intergalactic space-time) taken into account in Big Bang cosmology? Since from the POV of a singularity or a photon, their clocks have effectively stopped and any lower...

A reference please to a review paper, textbook, or website for an expression, or development of an expression for the field in Electro weak, similar to the A field in EM.

I know this is a basic question, but I haven't understood deeply what a inertial frame of reference is, to be more specific, its relation with the first law of motion.

What is the rate of expansion of the universe and what is it's acceleration rate of expansion? Exactly? I recall it's about 67km/s at 1 mega parsecs? But then what's the acceleration rate? This exact information I cannot find. If the universe is expanding, and this expanding is accelerating...

Hey PF, I am working on a problem set, and one of the problems is proving that the Christoffel symbols vanish at the origin of the coordinates ##y^{\alpha}## given by the coordinate transformation: $$y^\alpha (x) = x^\alpha - x^\alpha_{(0)} + \frac {1} {2} (x^\mu - x^\mu_{(0)} )(x^\nu -...

Homework Statement Two images are attached. The first image details the problem. The second image has an x',y' coordinate system depiction of the problem. Homework Equations The total energy of a particle is defined as E = mc^2, with m = γ*m_0. The Attempt at a Solution If the x', y'...

Homework Statement I am having a issue relating part of this question to the Galilean transformation. Question Relative to the laboratory, a rod of rest length ##l_0## moves in its own line with velocity u. A particle moves in the same line with equal and opposite velocity . How long dose it...

hello everyone, i just want to know about some good reference to learn high energy physics, maybe with some examples for real world practical application... and i heard that old books with this topic is far better than the new ones, can anyone here recommend a book or two? thanks before and i am...

I'd like to learn about the MWI. I know undergraduate level QM (Copenhagen) and can, within reason, cope with a mathematical formulation of it. What's the best reference for learning the MWI? Thanks

I am looking for articles or books that would clearly and succinctly state the open problem of and issues with computing hadron masses and spins in QCD from first principles, preferably in relation to the open problem of confinement and the general open problem of non-perturbative QCD. Any...

Let's suppose we are given a set of requirements and we are to design a motor that meets them. Requirements are: 3 phase synchronous, 480v, 50Hz and of hysteresis type and alnico is the only available option and it should deliver a 0.6N.m output torque. Dimensions should not exceed 150 mm and...

I have a ball of mass m that is situated on horizontal plane on the northern Hampshire. I am asked to show that the ball is moving, clockwise, in a manner of r = v / ( 2Ω*sin(λ) ) where v is the ball's velocity, Ω is Earth's angular velocity, and λ is the terrestrial latitude So here's what...

Hi here is the situation; There's a spherical particle contained with a MEMS sensor (3D accelerometer and gyroscope) moving down a bed. What we want is to estimate the total kinetic energy of the particle. The total kinetic energy has two parts, translational part and rotational part. for the...

Homework Statement The position of a participle in a fixed inertial frame of reference is given by the vector r = i(x0 + Rcos(Ωt)) +j(Rsin(Ωt))where x0, R and Ω are constants. a) Show that the particle moves in a circle with constant speed Homework Equations F = mv2/r The Attempt at a...

Homework Statement 3. (a) If an object's acceleration is zero in one inertial reference frame then is its acceleration zero in all other inertial reference frames? (b) If an object's velocity is zero in one inertial reference frame then is its velocity zero in all other inertial reference...

Homework Statement Which of these situations describes you observing from an inertial reference frame? a. you are in the car of a train, seated at a table, and the train suddenly slows down b. you are in the car of a train, going north, and the train goes around a curve to go west c. you are in...

Do you really need to absorb an advanced paper to answer the question? Let's view the problem this way: The ship is traveling at a constant .999c relative to Earth just prior to reaching Earth The ship puts on the brakes moments before reaching Earth, so that it is now at rest relative to Earth...

Homework Statement a) Alice is observing a small ball of mass m in relativistic motion bouncing elastically back and forth between two parallel walls separated by a distance L with speed u. After each collision it reverses direction, thereby creating a clock. What does Alice observe as the...

This must be a basic question. :) Bob and Alice have the same age. So in special relativity Bob leaves Alice and travels at very high speed and when it returns is younger than Alice. Bob's time is dilated and his space is contracted from Alice frame of reference. But now, if I take Bob's frame...

Can someone please show that calculation of gravitational potential energy at a point R+h from the centre of the Earth by choosing the centre of the Earth to be at zero potential. Here R is the radius of the Earth and h is not very small wrt to R

I am reading through a textbook on AP Physics, and I came across a few references to non-inertial frames of reference. It doesn't clearly say what a non-inertial frame of reference is. Based on the examples it gives, I assume that it is a frame of reference where the observer is experiencing...

The SI definition of a second was originally based on 1/86 400 of a day - but the Earth's rotation is a) unsteady and b) changing so it was changed to a defined number of cycles of an atomic clock. Was there a specific day for which the atomic clock was calibrated? Put another way, why were 9...

I want to make a comment on the Oppenheimer Snyder collapse, and before doing so want to read the original Oppenheimer Snyder paper. All I have been able to find is the paper "On continued gravitational contraction" in the Sept '39 Physical Review, but I get the impression that to most people...

Homework Statement Imagine that you are flying on an airliner on a long flight to Europe, at a constant speed of 300 m/s. a) You throw a ball towards the back of the plane at 20 m/s. You then shine a beam of light towards the back of the plane. How will these two things—the ball and the...

I don't know what's the appropriate title for my question but here it is: What's the reference we consider to measure the speed with respect to when we say that as the speed of a moving object approaches the speed of light the time becomes slower in the frame of this moving object.

Hi, Sorry for this weird question. My computer crashed and also the notes in it. I had a book wherein I'd written all the formulae. There is one formula in notes of Power System. X = cube root of R. I remember there was a website that even had its derivation, but I don't have the bookmarks...

Hi there guys, I was wondering does anyone have a layman's explanation of the GCRS as defined in the title. I am confused as to whether this is an inertial or non inertial system. In text modern reference books such as this (chapter 10, section 10.3.2) they define rotating/non rotating...

Hello, i need help with my code please , i have a file named 'bic' which contain only 2 columns . I want to plot this two columns. Data=importdata('bic.dat'); g=Data.data(:,2) r=Data.data(:,1); delta=r-g; plot(r,delta,'b*'); And i have this error struct contents reference from a non-struct...

Imagine such situation: A bus is moving at constant speed, a man is standing on the bus and is not holding to anything - he is simply standing. Now, the bus starts breaking with constant negative acceleration and so the man will change his relative position due to the force of inertia. Now...

Hi. Can anyone recommend a text introducing differential forms along with all the necessary pre-requisites for understanding them? For example, I'm not really familiar with tensor calculus but would like to shortcut studying it completely separately to learning differential forms. If that's too...

I'm aware that there are definitions of how reference frames translates to mathematics. But I've came to the following. How incomplete would be to say that, mathematically speaking, two Lorentz (or whatever) inertial frames are two subspaces of a given vector space whose span is the same vector...

Homework Statement 1. Two skateboarders start from rest on opposite sides of a ramp like the one in the image, roll down and collide elastically on the level part of the ramp. The masses of the skateboarders are m1 = 48 kg and m2 = 55 kg and they both start from the height h = 4.70m. Ignoring...

Homework Statement My professor gave us a werid question which is as follows In the laboratory frame, two clocks are synchronized and measure two light sources at the same time situated at 3 years in time axis and 3 light years and 2 light years in x-axis >At what velocity is the frame ##S'##...

Given -5π/6, find the reference number. Let r = reference number I decided to graph -5π/6. r = -π - (-5π/6) r = -π + 5π/6 r = -π/6 Book's answer for r is π/6.

1. Find the reference angle given 60°. Let R = reference angle I decided to graph 60°. We are in Quadrant 1. R = 90° - 60° R = 30° Book's answer for R is 60°. 2. Find the reference angle given - 60°. I decided to graph - 60°. We are in Quadrant 4. R = -90° - (-60°) R = -90° + 60° R...

Homework Statement Imagine that you are flying on an airliner on a long flight to Europe, at a constant speed of 300 m/s. a) You throw a ball towards the back of the plane at 20 m/s. You then shine a beam of light towards the back of the plane. How will these two things-the ball and the...

Entangled states are only separable relative to certain basis states. So does that mean that reference frames have importance beyond those in spacetime?

Hi! Can anyone recommend a good introductory book for measure theory? I've found Terence Tao's online book to be a good start, but would I be asking too much if I wanted something even more introductory? Ultimately I'm working toward Ergodic theory (and probability theory along the way) with...

Suppose we have a rotating frictionless disk and there is a rotating observer on the center of it. Furthermore, suppose a very small ball on the disk's edge. Now we clearly know that the ball is not moving but the rotating observer sees the ball following a circular path with an angular velocity...

Mod note: Moved from a Homework section, as this is more of a conceptual question than an actual homework problem. I can't really memorize the unit circle, but I do remember my instructor teaching us how to use reference angles to evaluate any trig function without needing the unit circle. I was...

In the past, many others have asked this same question. Some teachers and professors have discouraged using Wikipedia. Articles in Wikipedia are followed by a list of books and references for further study. Except for string theory and loop quantum gravity theory, physics is less "political"...