Frame Definition and 1000 Threads

TL;DR Summary: about the Special Relativity Can a rest frame be chosen for the center of momentum for a system of two photos?

Hi all, I am working on the following Moment Resisting Frame: The frame has the following structural properties: E = 2.1E+08 % Modulus of elasticity; I = 0.000117 % Second moment of area L = 5; % Frame width h = 3; % Frame height I want to compute the total static stiffness of the...

All three questions concern general relativity. 1. Does the curvature of spacetime depend on the frame of reference? 2. Does kinetic energy exist? 3. If it exists, does it contribute to the curvature of spacetime?

Hi there, everyone, I have been working on a problem in which I would like to calculate the load shares and deflections of structural elements in a multi-storey building. These elements include moment-resisting rigid frames, diagonally braced frames, concrete cores, and shear walls. Thus far...

Hi, I'd like to find the easiest way to solve the following braced portal frame statically (at least for deflection and maybe stress if possible, no need to account for buckling here - reason explained below): Of course, I could utilize symmetry: But the problem is still that it's a...

Hello! Is there any work which looks at the frame dragging effect due to a rotating quantum object (e.g. in an eigenstate which is a spherical harmonic)? I would appreciate any reference on that.

Some Machian theories propose that its the relative acceleration of the universe opposite to the acceleration of an object that causes dragging linear inertial forces on the object. But how do they explain deacceleration of the object when the relative motion of the universe is de-accelerating...

Picture of the problem: I wanted to use this formula: (From Classical dynamics of particles and systems Book by Stephen Thornton) O is inertial observer. O' is non-inertial observer. I think ##F## and ##\ddot R## and ##\dot \omega## are ##0##. According to O' the point mass has velocity of...

In the case of two rulers of equal rest length moving past one another ibex posted the minkowski diagram and I have a question about the one diagram that follows the following comment by him: Note that, in the primed frame, "State 2" is after "State 3"! This is the relativity of simultaneity...

I'm looking into center of mass and I saw the derivation of: ## V = \frac{\sum\limits_{i = 1}^{n} m_iv_i}{\sum\limits_{i = 1}^{n} m_i} ## I understand how it's derived, so no need to explain this further. It's a velocity of the frame in which total momentum of our objects is zero. Forget...

When an object is in freefall, it is in a locally inertial frame of reference. If two objects are in freefall, can their locally inertial frames of reference have different relative velocities?

This was a practice question, so it had the answer with it, which is 31 minutes. However, I'm confused as to why Lisa experiences T0. It isn't exactly an event happening in Lisa's rocket, but rather her just moving through space. From her perspective, it should look like Earth is moving at the...

I'm building an aluminum tandem axle (7k total capacity) trailer. Boat (18'/1300#) on the rear and a Ryker Can Am 3 wheel (750#) on the front. It's a 23'-6" x 6'-8" bed. Max live load will be approx 2250#. 900# frame weight. 230# axles. I'm testing beam sizes with online calculators and need...

So for this problem I have already solved for the Y forces: Dy = 171.43 N, Cy = 228.57 N, and By = -428.57 N. For the X forces I split up the frame and took the moment of DE. Me = 1.5(300) + 3.5(300) - 5(Dx), Dx = 300 For CD Dx = -Cx fo I got Cx = 300, as when you forces are two member Dx =...

Hello! I have a radially pointing electric field i.e. at a given radius, R, the electric field has the same magnitude and points radially around that circle of radius R. I have a particle moving around that circle of radius R, with uniform velocity (ignore for now how it gets to move like that)...

The first thing I did is to get the value of ##N_A## by the equaiton of ##\sum{}^{} M_B=0 \rightarrow 650*0.4+450*0.45+400=N_A*0.6 \rightarrow N_A = 104.2N## This is the first. The magnitude of the reaction at B: ##\sum{}^{} F_y=0 \rightarrow B_y=450+650,\sum{}^{} F_x=0 \rightarrow...

can you check if I sketched it correctly? And please if you know any good resources refrence it.

Well people i want to go from my steel/aluminum frame to the best material in the market. I have seen that exist a relation between Mpa(Yield strenght-elastic limit)/density but i get a very weird relation in a strange unit (m^2)/(s^2) which is the expansion of a growing area in the time, but...

I have a rocket and it is moving straight from a point P with a velocity ##v##. When I say that ##x'=0## is at the place we sit in the rocket, then when the event happened outside his rocket at the point P, can I say that the coordinate of the event is for him negative, so ##x'=-vt'##, although...

Why force at D need to be parallel to force at E and F?

So i solved this question through non inertial frame but how do i solve this through inertial frame , when i used to solve only translation question when i observed through non inertial frame the main difference was in inertial frame Fnet = 0 and in non inertial frame Fnet -ma =0 (ma being...

SR interpreted as having no absolute frame of reference and an absolute frame type version of SR, where the speed of light is isotropic only in one undetectable frame are considered equivalent, since they use the same math. But here is a scenario in which I don't see how the physical predictions...

what would be the y'-x' ##\vec r## vector be? I think it is ##\vec r = (8t - 1) \hat i + (6t - 2) \hat j## (not sure whether it is correct or not.) I thought about it as at t = 0 the position needs to be -1i -2j so that is why I took the signs in the y'-x' frame position vector as a - instead...

My question is about the precise definition of what is being referred to as “physical frame”, in particular in the context of cosmology. Is it simply the observational frame in which physical units are held constant? Is the FLRW frame physical? A good reference would also be helpful. Thanks for...

From the top of my head, I would say that yes, the very moment our clocks are aligned, and the two bullets are launched it is perfectly ok to use the relativistic velocity addition formula to determine the speed of the bullets from my reference frame. But the more the disk keeps rotating, the...

I'm trying to make sure I understand how the traveling twin tracks the time of his stationary earthbound sibling and the time of another stationary observer who's farther away. From what I've understood until now, it's pretty straightforward with the earthbound twin: In the traveler's frame, the...

Have identified what i need to find, but not sure how to proceed since there is a pin in the centre, do I treat it as two separate structures?

I have tried to solve this problem using the lagrangean approach: $$L = T - V = m((\dot r)^2 + (r \dot \theta)^2)/2 - 0 = m((\dot r)^2 + (r \delta)^2)/2 - 0 $$ The problem is that the answer i got is the right answer at the smooth rod referencial, that is, at the non inertial frame. Now we can...

Summary:: 12 ton rectangular frame is lowered by a 4 point crane attached to each corner of the frame. Frame will be lowered onto plastic supports, these supports have guiding ramps of 60 degrees to help the operator lower the frame in the correct spot. The frame has 4 feet, one on each corner...

Just wondering, is there a frame of reference, among all of the different frames of reference, where someone dies before they are born?

I was starting out some problems on force and motion at 10+2 level. I was told you don’t need to know about frame of reference. But I want to. So which books are there to understand frames? Is it a part of relativity? If yes then which books? Thank you guys.

Hello all, I have a question on a pivotal concept of GR that I've never managed to fully grasp. In what coordinate system is the Einstein's Field Equation set up and solved? I've always assumed it's an Euclidean 4D space, whose metric is irrelevant because we are dealing with scalar...

There are some question involving the statement. One of them is about the charge density in S' frame. It asks to calc it. I thought that i could calculate the electric field in the referencial frame S' and, then, use the formula $$ E = \lambda / 2 \pi \epsilon l $$ In that way, i would obtain...

It's frequently discussed Galilean transformation brings one inertial frame to another inertial frame, and such a transformation leaves Newton's second law invariant (of the same form). I wonder what happens for non-inertial frame? If we start with a non-inertial frame, and Galilean transform...

Two clocks with photo detectors are 100 kilometers apart at A and B. On the center of AB axis two light pulses are sent to the clocks , synchronizing them. Then a light signal is sent from A to B. The two stationary observers record the time from event at A to event at B. Is there a one way...

My answer is (A) since I think the motion of the spacecraft will alter the length of the spacecraft (length contraction) but not changing the orientation so the angle will stay the same But my teacher said my answer is wrong. What is my mistake? Thanks

Just want to clarify some concepts. There seems to be difference between reference frame and coordinate system. See https://en.wikipedia.org/wiki/Frame_of_reference#Definition . A reference frame is something has physical meaning and is related to physical laws, whereas coordinate system...

In learning about translational and rotational motion, I solved a problem involving a wheel rolling down an inclined plane without slipping. There are multiple ways to solve this problem, but I want to focus on solutions using energy. Now to my questions. The reference frame in the posted...

Hi all, Currently I am working on a home-project, making a trike. Now just for fun and because I like to calculate things, I calculated the deflection of a frame with a load. The frame is shown in the picture below, I added the force for clarity. With my analytical calculation I found a...

If I have fluid with area 10 and velocity 10, if the velocity increases to 20 the area will become 5. But if we switch to a reference frame moving at velocity 1 opposite this motion, then it would be 10 and 11 to 5 and 21, violating the continuity equation. What is wrong?

v1 - velocity of the rain with respect to the ground v2 - velocity of the man with respect to the ground v3 - velocity of the rain with respect to the man So, v1 = v3 + v2 is this right ? So, for the man moving with a velocity v2 with respect to the ground, the rain will have a horizontal...

Say 2 cars are traveling side by side at 10 m/s in some flat, wide open space. Relative to each other they are stationary. Relative to someone on the ground they are both moving at 10 m/s. Now say you're in 1 of the cars and you see the other car accelerate, changing his velocity by 10 m/s in...

I'm having trouble with Rovelli's new book, partly because the info in it is pretty condensed, but also because his subjects are often very different from those in other books on GR like the one by Schutz. For one thing, he never uses the term "manifold", but talks about frame fields, which seem...

Take this video as an example. Its an attempt to humanize the hypothetical experience of free falling into a black hole.When I consider this video, the proper time of the traveler in crossing the EH is intuitively preferred for me, and the proper time of an observer on the spaceship as they...

Hi, reading the Landau book 'The Classical theory of Field - vol 2' a doubt arised to me about the definition of synchronous reference system (a.k.a. synchronous coordinate chart). Consider a generic spacetime endowed with a metric ##g_{ab}## and take the (unique) covariant derivative operator...

Here's what I did so far. The velocity of the first car is ##v = v_0 +at## Frame of reference S = the road Frame of reference S' = the second car thus, v' is the speed of the first car in the frame of reference S' and v the speed in the frame of reference S. Here's what make me doubt. The...

Is energy always conserved in a co-rotating/accelerating frame?

If a train is moving at some constant V with a bed sitting still on top. When the train decelerates at some rate -A then the bed will move at some acceleration A. I can't seem to get an intuition for how this comes to be. I have looked online and find no help.

Hi, starting from this old thread GPS clock synchronization I've a doubt about the physical process employed to synchronize clocks bolted on GPS system satellites. We said that clock synchronization is frame dependent. In other words we must select a coordinate chart (aka reference frame) that...