Frames Definition and 610 Threads

Let me set the stage for a thought experiment. 1. A physicist in an elevator at some arbitrary height above Earth holding an accelerometer oriented in a direction pointing toward the center of the Earth. 2. No atmospheric drag. Drop the elevator car and make a measurement. The...

If I stand on the surface of the Earth holding an object from my frame of reference I do no work because the object is at rest and the displacement is zero. However from the frame of reference of a second object moving toward the Earth the first object would be moving up and I would be doing...

By a frame I mean four orthogonal vectors for which one is timelike and the others are spacelike. In a bypassing some time ago I read something about the basis vectors in a frame representing sticks and and a clock. However, the author also noted that this interpretation was problematic. I...

hello i want to derive the Transformation of acceleration between two reference frames i searched in internet and found a book but i don't understand just one step i attach a picture so you can see what i found in the internet my problem is eq. (1.10) \begin{align}du=\frac{dU}{\gamma...

Homework Statement An astronaut is traveling in a space vehicle moving at 0.500c relative to the Earth. The astronaut measures her pulse rate at 75.0 beats per minute. Signals generated by the astronaut’s pulse are radioed to the Earth when the vehicle is moving in a direction perpendicular to...

Hi All Let me start by saying that I am new to this forum and I am new to physics. I've always had an interest in getting an entry level understanding of Newton's Laws of Motion. I also apologize if these questions are a bit stupid or overly covered in other posts. I watched a Yale video...

Hi, I'm going deeper in basics points on general relativity but, instead of swimming directly between the differential geometry, I'm trying to base my knowledge on strong physics bases first. I'm studying both on Wheeler's stuff ( I'm collecting almost all his books ), directly on Einstein's...

Homework Statement Two clocks located at the origins of the K and K' systems (which have a relative speed v) are synchronized when the origins coincide. After a time t, an observer at the origin of the K system observes the K' clock by means of a telescope. What time does the K' clock...

Hello to everybody, the question seems trivial in my mind, yet, is it legal to say that there is not unique frame of 0 total momentum in the Minkowski spacetime plane? I am thinking of two non-accelerating equal masses on a horizontal plane, one is moving horizontally, the other...

I was just wondering what would the definition of the inertial frame be, since as I've understood the description it seems that an inertial frame seems to be 'free' from any external forces, correct me please if I'm wrong. Can something be an inertial frame even if gravity acts upon it? For...

This paper discusses the Bell spaceship paradox: Petkov, "Accelerating spaceships paradox and physical meaning of length contraction," http://arxiv.org/abs/0903.5128 PF has a FAQ on this paradox: https://www.physicsforums.com/showthread.php?t=742729 My purpose in creating this thread is *not*...

Hi I am working on a robot that has a spinning 3D laser scanner. It rotates about two axis and collects data. In one axis it has full 3D rotation and in another axis it has limit rotation. Now the read world points collect by this laser scanner is not unifomaly distributed but if...

Homework Statement So I'm having some trouble understanding this paragraph from my textbook. I was hoping that maybe someone could explain it to me. For example, we can assume that the ground is an inertial frame provided we can neglect Earth's astronomical motions(such as its rotation)...

Bit confused regarding how non-inertial frames can be treated in GR (and by non-inertial i mean affected by some kind of four-force). Can anyone give a brief summary or link to some good sources?

I was wondering how is our perception created according to relativity, since what we perceive depends on the perspective we have on the space-time around us. If two events are simultaneous in our frame by deduction from our perception we will realize that they are, and that the causal process...

A racquet ball with mass m = 0.245 kg is moving toward the wall at v = 15.4 m/s and at an angle of θ = 28° with respect to the horizontal. The ball makes a perfectly elastic collision with the solid, frictionless wall and rebounds at the same angle with respect to the horizontal. The ball is in...

I was reading a little about the behavior of non-inertial frames in relativity, since I'm interested in knowing how can we measure time on Earth and the sequence of events here. So as we know Earth is rotating and therefore the clocks on surface that are mutually at rest get desynchronized. Can...

Hi guys, this is my first post, I'm a newbie regarding physics and relativity so I hope you can help me here. I've just recently started learning about relativity, and my question will be about the relative simultaneity, or precisely Andromeda paradox. So in the original setup, if an...

I know there are many wavefunction collapse models - but with regards to the Copenhagen interpretation the idea is that a measurement will cause something to collapse into a particular state. What does the term "measurement" refer to? It makes one think of only something that a conscious being...

Hello, Lately I have been wondering about the implications of the speed of light being constant for all observers, to me this seems to imply that there are different versions of reality for different observers. I will use a scenario to illustrate my reasoning. After you read this I would like...

A person is inside a car. This person is not using the seat belt. The car crashes with a solid wall and decelerates quickly. The person, due to inertia, keeps moving until stopped by the wind shield. I want to analyze the movement of this person after the crash, but I am troubled...

Hello, I would like to prove that the time experienced in a moving reference frame is longer than in a stationary frame. Here is my solution: Suppose that at time t = 0 two reference frames, S and S', origins coincide; similarly, the x,y, and z axes of the S-frame overlap with the...

https://www.amazon.com/dp/3642372759/?tag=pfamazon01-20 http://www.springer.com/physics/theoretical,+mathematical+%26+computational+physics/book/978-3-642-37275-9 I have just ordered (actually, my wife did, but she has yet to realize this :biggrin:) this new, comprehensive, advanced book on...

I was trying to do some studying regarding the definitions of energy, and I've hit a road block. I know that since velocity is frame-dependent, an object's kinetic energy as observed in two different frames will yield two different results. My initial expectation was that changes in...

Hi all, think this might be a silly or trivial question but I've got myself in a bother so thought I'd get some help. Best to illustrate my question with an example. Take a vector expressed in some chart, then we can find the components of that vector in another chart in the standard way by...

Hi, I've been trying to understand the (lack of) simultaneity between events in reference frames moving wrt each other. I'd be grateful if someone could confirm that I've got things right: If two events are simultaneous in one reference frame (S'), then they will not be simultaneous in a...

My question stems from a conversation I had recently with another physics buddy of mine and has to do with rotating reference frames and acceleration. Say, in a non-rotating reference frame you have an object with a known position. For the sake of argument, say it has a position A of 0i + 2j +...

Sorry if this is a frequent topic, but I think it's interesting and probably worth repeating if it's come up often before. Let me lay out my question by example (and if anything is inaccurate feel free to point it out), and then I'll summarize at the end. It's easy to show in Classical...

K'sys=1/2MtotalVcm2+1/2\muVreli2 I understand this equation represents the total kinetic energy in a reference frame. What I'm not getting out of this is the overall concept. I understand that the first part of the equation is supposed to represent the total kinetic energy required to...

Say a ship is coasting in space at an arbitrary speed and velocity with respect to an observer. If a joule of energy (generated on the ship) is used to instantaneously accelerate the ship: From an external observer, the acceleration and delta-v observed is dependent on the ship's initial...

Basic question I'm sure, but here goes; If the following is correct; An object may be considered to be 'at rest' when there are no inertial forces acting upon it (ie; it is not accelerating). A satellite is at rest because it is in freefall. A person standing still on the Earth's...

Hi, before I question let me say I'm new both to this site and Physics in general, as such please forgive any ignorance on my part. I was given an example of time difference in regards to a 'my twin traveling at near the speed of light' scenario and I'm having trouble reconciling some of the...

It's a pretty straight-forward question, and it got me confused since most articles on the internet mention planes of simultaneity in the context of inertial frames. So if rotating frames also have planes of simultaneity, what SR says about it and how does it differ from the planes of...

Hi guys, I was reading some stuff about general relativity and the first impression is that isn't completely the follow-up to SR. In what I've read it has a different assumption about inertial frames, that they are only significant only locally. What does this really mean and what are the...

\vec{r}_a is a positional vector from reference frame a. What is the position of same point from reference frame b ? If required, assume position of origin of frame a is \vec{m} and unit point (i.e. \langle 1,1,1\rangle_a ) is \vec{n} from reference frame b. I am studying Kleppner and Kolenkow...

I have a question about Earth's rotation around its own axis. Earth rotates at around 1000 miles per hour. However, if I stand in an open field and let a balloon float beside me in mid-air, I wouldn't expect the balloon to fall away (or appear to fly away) at that speed when I let go of it. I...

I am currently working on a Python script to simulate motion of reference frames wrt each other, and I need some help with the math. Here is the problem statement- Suppose I have a frame A A frame B frame B's origin has pos-vector PB,A (function of time) wrt A in frame A frame B is...

Homework Statement I am sort of reviving this thread. https://www.physicsforums.com/showthread.php?t=182511 My question is the same. I understand and agree with what fisix responded a few years ago. Homework Equations cos( θ)= v_cart / v_bullet The Attempt at a Solution I can...

Overlapping reading frames in influenza viruses allow two proteins to be coded into the same RNA segment, but only by what appears to me as an enormous coincidence. the analogy I came up with is that overlapping reading frames are like taking a book, and moving every space one character to the...

Homework Statement A bug of inertia m_B collides with the windshield of a Mack truck of inertia m_T \gg m_B at an instant when the relative velocity of the two is \boldsymbol v_{BT}. (a) Express the system momentum in the truck’s reference frame, then transform that expression to the bug’s...

Hi, Basic question. I'm confused by a time dilation example (37.3 in Young and Freedman 11th ed.). Mavis is moving at .600c relative to earth-bound Stanley, and at the instant she passes, both start timers. Part b asks "At the instant when Mavis reads .400 s on her timer, what does Stanley...

Do we measure different frequencies of light in frames moving relatively at constant velocities? Because when we look at an annihilation reaction from the view of different frames, we see different energies of the reactants which seem to affect the frequency of the produced photons. your kind...

I'm hoping you can help with a debate I'm having with a friend regarding whether throwing a ball in a headwind is the same or different from throwing a ball from a moving platform (lets say an open boat). If you want some numbers, could you please work with these: For the static throw, can...

Homework Statement (a) Show that E2 - p2c2 is a Lorentz invariant, where E is the total energy, p is the momentum, c is speed of light. (b) In the lab frame, an utlra-relativistic electron with γ = 100 collides head-on with a photon of energy E. Find the threshold energy E required to...

Homework Statement Homework Equations The Attempt at a Solution E2 - p2c2 = E02 I know that this is true. But how do i relate p1 to p1'? and same for energy as well. I expanded the LHS= E0,12 + E0,22 + 2E1E2 - 2(p1c)(p2c) for the RHS = E0,12 + E0,22 + 2E'1E'2 -...

Hey guys. I'm having doubts about something in a GR text I read (Gravitation - T.Padmanabhan). In general, for Lorentzian 4-manifolds, we call a basis of smooth vector fields ##(e_{\mu})^{a}## (that is, a set of smooth vector fields that define a basis for the tangent space at each event of...

Previously, before getting into relativity, I've always thought of a 'reference frame' of basically an "observer carrying a coordinate system" - where I thought of an observer as anything which could record information of positions and velocities of particles etc. Now, however, I'm reading a...

If any of you have the Third Edition of Classical Electrodynamics by John David Jackson, turn to section 11.8, as that's where I'm getting all this from. If not, you should still be able to follow along. In said section, Jackson gives us this equation that relates any physical vector G in a...

Homework Statement In frame F there are two lights on the x-axis at D and -D (D=0.6x10^9 m ) which flash simultaneously when t=0. There is another frame F' which moves at v=0.8c in standard configuration with F. I need to work out when observers standing at the origin of both frame F and F'...

Homework Statement (see attachment, ignore those marks done with the pen) Homework Equations The Attempt at a Solution I think this has to do with calculating torques and forces but I don't know about which point to calculate torque about. I know this is a very less attempt...