Frame Definition and 1000 Threads

I apologize if this has been asked before. I searched numerous times and couldn't find any discussion on this specific topic. Every description I've read of the impossibility of FTL signaling uses some variation of this diagram: http://www.theculture.org/rich/sharpblue/archives/000089.html...

Consider I am in the train with a ball traveling at normal speed of a train. I drop the ball, it follows a straight path of descent and falls in front of my feet. For an observer on the platform, the ball follows a parabolic path and falls in front of my feet. (Please go to this...

A recent forum thread went into a long disussion of simultaneity. The term "ansible line" was used (later referred to as a "simultaneity line.") Einstein demonstrated with a thought experiment with regards to lightning and a moving train that events can be simultaneous in one time frame but...

Is it possible to deifine local inertial frame which is Poincare invariant (in general relativity) (every manifold is locally flat, so we can chose coordinates which are almost pseudoeuclidean, but in what sense they might be Poincare invariant) Thanks.

I was just working on my knowledge of the twin paradox, and had a question that I couldn't find an answer to anywhere: If I understand it correctly the paradox is resolved because the two frames are not symmetrical, one is non-inertial, so that frame has it's clock run slower. So if you carry...

I understand the Michelson–Morley experiment and its result; but what I don't know yet is the REASON. Example: A torch in free space is moving at a velocity [v] w.r.t me. Considering the material nature of light, shouldn't the speed of photons emitted from the torch be [v+c] w.r.t ME? According...

It seems clear that all inertial frames would agree that a frame was accelerating based on instantaneous (short interval) relative velocity measurements. That all frames would agree that the velocity was changing over time relative to their own frame but it is not so clear if they would all...

Homework Statement Consider an elastic collision of two particles in the centre of mass frame. Briefly explain why the speed of EACH particle after the collision is the same as before the collision. (FYI this is exam revision so it isn't worth any marks) The Attempt at a Solution...

Here is the problem: (Question 5-2 in Binney&Tremaine Galactic Dynamics) Consider a homogeneous self-gravitating fluid of uniform density \rho_0 contained within a rotating cylinder of radius R_0. The cylinder and the fluid rotate at angular speed \Omega about the axis of the cylinder, which...

Take the following setup: A series of pulses of radio signal is relayed around the world, along the equator. There is no "gap", it is a continuous loop along numerous relay stations build along the equator. The total number of pulses is fixed at 648,000 - I'll explain in a minute why that...

I'm trying to get a metric in the frame of a boosted observer. The spacetime in question has coframe and frame basis vectors \begin{align*} \vec{\sigma}^0 = \frac{-1}{\sqrt{F}}dt\ \ \ \ & \vec{e}_0 = -\sqrt{F}\partial_t \\ \vec{\sigma}^1 = \sqrt{F}dz\ \ \ \ & \vec{e}_1 =...

Exterior commercial frames (.053") embedded in a concrete wall 8" thick with 3" layers of polystryrene (3# density) on each side of concrete cavity. Frame rests on foam inside and outside of building. Frame is grouted solid with poured in place concrete. Is there an appreciable (to be...

Considerer a closed box into space: • In constant acceleration. • Turning around its axis. Einstein used the first case as a thought experiment (http://galileo.phys.virginia.edu/classes/252/mass_and_energy.html) that led to the general theory of relativity: the occupant of the box could...

Does the graviton move at the speed of light in any reference frame? Thanks, Jake

If velocity is subjective to an observers frame of reference, then isn't energy (kinetic) also subjective? How can we define energy as objective if it changes depending on your frame of reference?

https://www.physicsforums.com/attachment.php?attachmentid=25852&d=1274225973 The A side, move down ward. The O is a pin, with no friction. The A and B have their own mass. The length of the stick or beam or frame is known. How to describe the energy of A down word until reach high h? i...

Could an observer in a gravity well perceive a particle to be a differnt type of particle than an obsever who is outside of the gravity well? Can an observer in one frame see a hydrogen atom and an observer in another frame see a neutron?

Homework Statement Hey guys and girls I have tried to solve this one but I got part (b) wrong any help would be awesome :) A picture hangs on the wall suspended by two strings, as shown in Figure 6-24, with θ = 72°. The tension in string 1 is 2.0 N there is a picture with two strings...

See "linear frame dragging" here: http://en.wikipedia.org/wiki/Frame-dragging Two small masses, initially the same distance from a large mass. One of the small masses has a propulsion system that keeps it at a constant distance from the large mass. The other small mass has no propulsion...

I have came up some question asking the velocity change of the rocket in its instantaneous rest frame. And I have been taught that in the instantaneous rest frame, v=0, dgamma/dt =0, gamma = 1. if v is always zero, how come to talk about the change in velocity? Thanks in advance

Let's consider flat 4D Minkowski spacetime. Is it possible to define (local) coordinate system for any observer (its natural reference frame) so that these coordinates posses interpretation of time and spatial position measured by this observer? It can be done in two dimensional Minkowski...

After picking up passengers, a train accelerates uniformly until its speed is 100 km/hr at t= 300 s. If during this time it is traveling on a planar path that approximates the circle and line shown in the figure, find the magnitude of the train's acceleration when (a) t = 1 min and (b) t = 2...

Homework Statement I'm using MATLAB show the path of a projectile fired directly up(directly out from the center of the earth) from 41 degrees north latitude. Air resistance, variation of gravity cause by height, and the centrifugal force are for now ignored. What I'm trying to figure out...

Hi, my question is this, say you’re in a lift that is accelerating downwards at 5ms and you were to drop a 200g wallet from say 1.3m off the floor of the lift, assuming gravity is 9.8ms, how long would it take the wallet to hit the floor of the lift? Does the downwards acceleration of the...

Now then, this is a past paper question for only 3 marks but its annoying me. 2 identical spheres undergoing an elastic relativistic collision. The spheres move with a speed such that their CM frame kinetic energy is equal to their rest energy. Calculate the speed the spheres in the CM...

Problem: Calculate the velocity and acceleration from an inertial reference frame of a particle whose motion functions (in Cartesian's coordinates) are known from a moving referential. The motion of such a referential is in accelerated translation and rotation with respect to the inertial one...

we generally study the concept of Inertial reference frame in case of translation motion (for non-accelerated frames) what happen if motion is rotational?

Does the concept of Inertial reference frame also applicable for 2nd & 3rd law of motion?

Hi just a quick question, I've been searching online to find out if there is any measurable frame dragging effect on a high rpm massive rotating disc, but havnt been able to find anything. I've read a bit about gravity probe B but in my limited understanding of the effect and the physics around...

I'm not a physicist and not a mathematician. I just want to understand things, and have read "advanced layman" books. It's often touted that Noether's theorem shows that the uniformity of space (the same everywhere; no preferred origin) implies conservation of momentum. More properly, the...

In theory the set of Inertial Reference Frames could consist of an infinite set of rectangular grids and distributed clocks, overlaid and sliding through one another without interference. Let us say we are initially at rest at the Origin of IRF K. Relative to K, the grid of moving frame K’...

Why an accelerated frame of reference is non-inertial?

The other day, I was arguing that a car traveling 70mph rear-ending a car traveling 55mph is the same as a car traveling 15mph rear-ending a stationary car. My argument was that, from the frame of reference of the car that was traveling 55mph, the energy of the other car is k(152), where k =...

Homework Statement Granted, I may be thinking too much into this. You are sitting in a jet airplane as it accelerates at a constant rate down the runway. Being a good physics student you hold the string of a small pendulum of length l = 0.75m and mass m = 1 kg. You then measure the...

The fact that the relativity of simultaneity causes events to not happen at the same time, dependent on reference frame, seems to imply a separate universe or world for each and every thing in the universe. Different events at different times due to the relativity of simultaneity would lead to...

This question may be nonsensical, but I have to ask. I'm a noob to relativity so please bear with me. All observers measure the same speed of light, correct? We also know that there is no favored frame of reference. So... what is to stop an object from accelerating to 0.95c, taking a...

Does the principle of invariant light speed still hold in a non Inertial frame of reference? Thank you!

STUPID QUESTION ALERT! Is spacetime an absolute reference frame?

hello forum, i am struggling with the conceptual understanding of this problem: Given two blocks, one on top of the other. There is friction between the two blocks. The upper block is pulled with a force F. Thanks to friction, as long as F is smaller or equal to the static friction...

How can i find out aircraft's bank angle knowing it's local frame in horizon frame? Specifically, the horizon frame is y for up, z for north, x for east, the plane frame is x for right wing-wards, z for nose-wards, y for up. I know unit vectors of plane frame in horizon frame, and want to...

Hi there, Could anyone explain to me what is the different between the two terms (i) Original rest frame (ii) Instantaneous rest frame When do we prefer to work in the original rest frame but not the instantaneous one and why? And when do we prefer to work in the instantaneous rest...

I have a thought experiment I cannot resolve. Maybe someone smarter than I can resolve this. Suppose we have a long, thin rod, rotating in the counter-clockwise direction around a pivot axis which is at the end of the rod with an initial angular velocity equal to w. The axis is connected to a...

If the universe is finite and unbounded why can not we think of the frame that sits with it's origin at the center of the 4-D sphere as a preferred frame? The preferred frame?

What is a definition in GR that correctly captures the concept that a frame is rotating? Is it enough to say that it's stationary but not static?

hi all of u WHAT IS INERTIA? and Earth is a inertial frame of reference or non inertial frame of reference? tell me briefly.

Hi all, if I have the velocities and rotations of an object with respect to a moving frame. Are there relations that I can obtain the velocities and rotations of the object with respect to a fixed frame?

A square rigid metal frame PQRS, of side 12 cm, forms a closed circuit with an ammeter. It is moved through an enclosed region of uniform magnetic field of flux density 2.0 × 10–2 T, from left to right. The field is confined to this area and directed into the page. PQRS --> magnetic field -->...

So if I'm a fast object moving in a sphere, in my frame of reference the sphere begins to contract along the direction I'm moving. As I approach the speed of light, the sphere begins to deform into a disk. If I'm a photon, the sphere is a disk. Rather than requiring requiring 4 coordinates to...

I'm trying to wrap my head around how rotational frame dragging affects the centrifugal force of a massive, rotating body and was hoping someone could explain this concept to me better. If I am confused on any of the points below please let me know. It is my understanding that there is no...

Homework Statement A neutron with kinetic energy T= 2mc^2 (m=rest mass),strikes another stationary neutron.What will be the combined kinetic energy of both the neutrons in the frame of their centre of inertia and the momentum p of each neutron in that frame.what is the velocity of the...