Frame Definition and 1000 Threads

To my understanding the Relativistic Doppler shift is a product of the classical velocity shift and the dilation factor arising from that velocity. The classical effect can be red or blue depending on whether the emitter and receiver are receding or closing respectively. The dilation...

I have never understood why it's beneficial to do a collision in the cm frame, but then I did an example for myself and it was easier. I just don't understand why. I had two objects with masses m1 and m2 and velocities v1 and v2. I found the velocity of the centre of mass: vcm =...

I understand that the ~14.6 billion year age of the universe is in the cosmological frame, i.e., representing the coordinate time elapsed in a comoving reference frame. Of course this means (as has been discussed plenty of times here) observers in different frames would measure a different age...

Homework Statement http://img811.imageshack.us/img811/9092/captureykj.png The Attempt at a Solution The answer is also in the image above. I have no clue how to start this question. Could anyone be so kind to give me a hint on how I should approach this question? Thanks!

I have a regular curve, \underline{a}(s), in ℝN (parameterised by its arc length, s). To a running point on the curve, I want to attach the (Frenet) frame of orthonormal vectors \underline{u}_1(s),\underline{u}_2(s),\dots, \underline{u}_N(s). However, looking in different books, I find...

I had this as an exam question in my first Structural Analysis course, and couldn't figure it out. The frame is supported by 2 cantilevers at points A and D. The top member is perfectly rigid, that is EI=infinity. E is constant. Solve for the deflection at point B and the reactions at A and D...

It must be, right? Obviously, if you're pushing a block by exerting a force F on it over a distance D on the ground, if you are in the frame of you or the block, your distance is 0 so it appears you're doing no work. I ask this question because I was doing a practice problem that should be...

In studying SR, I've been subscribing to a particular definition of a Frame of Reference that makes sense to me. Recently, I've been made aware by another PF member that there may be other, broader, definitions that are valid and that people use. I would like to know more about these broader...

Practicing Lorentz transformations but still not absolutely clear about conditions for observer's frame of reference. For example: Suppose that just as one of Einstein's long and surreally fast trains is passing a station platform, lightning strikes the platform at two points making scorch...

One can easily prove that \nabla \cdot f is invariant under a rotation of the reference frame, however I would like to prove that the divergence operator itself is invariant (same principle, different approach). In other words I want to prove that \mathbf \nabla = \mathbf e_x...

\inthi all, I need just little bit of confirmation about what I'm doing. Normally I know how the stiffness matrix is composed for 2 node frame element in 3D space. which creates 12x12 matrix for that element, if there is also thermal loading on frame element additional...

I want to put a hammock in my room but don't want to damage the walls from putting too much lateral pull on a 2X4 stud. So I decided that I need a hammock stand, but don't want a huge ugly thing spanning my room. Do you think its possible to build two separate free standing supports that can...

Homework Statement I wanted to know if I consider the frame of reference as a rotating body itself, then will the points lying on the body rotating be stationary with respect to the rotating frame of reference? Homework Equations None The Attempt at a Solution As per me, if I am...

Hi there. I need help to work this out. A particle with mass m is studied over a rotating reference frame, which rotates along the OZ axis with angular velocity \dot\phi=\omega, directed along OZ. It is possible to prove that the potential (due to inertial forces) can be written as: V=\omega...

This discussion started as a side clarification of something in this thread https://www.physicsforums.com/showthread.php?p=3971013#post3971013 and although tangentially related it probably deserves a thread of its own so anyone can participate without reservations. Please keep in mind I am not...

Hello everyone, I am a new member here. Nice place you have; I have been reading on here again and again and figured it would be the right place to ask you about a problem I just can't get sorted out myself. It is about bicycles and disc brakes. I have an aluminum track frame that I want a...

Why is there no redshift in a freely falling frame? The photon in a freely falling frame also rises in the gravitational field, so isn't it supposed to be redshifted?

An elevator slows down with a 6 m/s2 acceleration and an object m=3 kg is freely released as shown in figure There is no friction between object an semispherical shape. The object reaches L point what is the force which the object exerts L point? A)120 N B)240 N C)360 N D)480 N E)600 N...

Is there any other object except photon which moves at the speed of light? Why can't an object moving at the speed of light be taken as reference frame? Can we use the equation m=m(0)/sqrt(1-v^2/c^2) for an object moving with speed of light?

In my book on waves, it is said that, given a flexible string under tension, a derivation of the transverse velocity v can be given by viewing the string in a frame moving uniformly with a velocity equal to that of the wave itself. The velocity can be found by requiring the uniform tension of...

Now, I've read that frame dragging will cause an effect likened to planetary gears, where the spinning source is the sun gear and the object is the planetary gear. Here's where I get confused. Suppose you had a straight meter stick aimed directly at a massive rotating object from an...

I meant which frames distance divided by which frames time gives the velocity of frame 2 wrt frame 1..I guess the 'v' measured from rest frame is different from v measured from other frame right(concerning time dilution since time always dilutes in frame 2 only).? Btw do u think their is a...

What significant features are present in the five or six most recent geological layers? In other words what is the basis for determining how much time has elapsed in these layers? Is it mostly based on the types of fossils or the types of soil or rocks in these layers? Also, is it easier or...

Please explain the concept of pseudo forces by considering an example of two cars say A and B, accelerating in the same direction. How will Newton's law applied to the man in car B as noted by the man in car A differs from that of the man standing on the earth? And how will the man in car A...

Does anyone know of a standard way of calculating the com frame velocity for two particles moving at arbitary velocities in the lab frame? It's strange that this standard result isn't even in Goldstein's et al book

I have no background in relativity. Recently I started reading some introduction to special relativity in Griffith's EM book, where he vaguely defined an inertial reference frame as one in which Newton's first law holds. Now according to this definition, does such frame exist in nature? On...

Hello friends Iam naveen and new to this forum.I have a question regarding the transformation matrix from world frame to the base frame of a Spatial serial manipulator. The frames are attached like this. The Z-axes are along the link lengths. The Xi axis is oriented such that Xi = Zi X Zi+1...

[b]1. every member is 0.45m and all the angle is 45degree... C is fixed support, D is roller support [b]3. Ʃfx = 0 , Cx = 0 Ʃfy = 0 , Cy + Dy = 20N ƩMc = 0 , 20(0.45) + Dy(0.45) = 0 Dy = -20N...

Can someone please explain to me (it can only be brief, I'll try to do the dirty work myself ^.^): Frame dragging in terms of: What is a frame, What are it's dimensions (2d/3d(x,y,z)) What does this have in relation to the Schwarzschild radius in terms of astrophysics; With that...

Homework Statement You are flying your personal rocketcraft at 0.9c from Star A toward Star B. The distance between the stars, in the stars' reference frame, is 1.0 ly. Both stars happen to explode simultaneously in your reference frame at the instant you are exactly halfway between them...

Homework Statement Specify and explain whether the following is an inertial or non-inertial observer: An observer is placed on a rock between Andromeda and the Milky Way. Homework Equations N/a The Attempt at a Solution So here is my understanding, the observer would be situated...

Hi, Physics Forums! This is my first post here and I know just about zero physics, so I apologize in advance if the question is a little daft/naïve. Ok, so here's what I'm wondering: suppose you have a light source that produces EM waves in all directions at some frequency ν, and a camera set...

Homework Statement Find CM energy of a mu+ mu- collider, with each beam having an energy E of 500 GeV. The beams cross at a small angle of 250 mrad.Homework Equations E^2 - p^2c^2 = m^2c^4The Attempt at a Solution So I have a diagram for the lab frame which has the mu- coming in at a small...

People tell me that we cannot extend our inertial frame, as defined in special relativity, across the Universe because that would be in violation of general relativity. The problem is that general relativity says that space-time can be curved whereas a global inertial frame assumes flat...

Homework Statement Determine the reactions at rocker support A and pin support B.Homework Equations ƩF = 0 ƩM = 0 The Attempt at a Solution ƩFx = 0: -Asin(25) - (800lb) + Bx ƩFy = 0: Acos(25) - (500lb) + By I'm getting thrown off because of the rocker on an incline.

Hi there! I'm working on a couple of problems regarding simultaneity. For one I'm given events X_a = (ct,x,y,z) = (2,1,-3,2) and X_b = (6,3,-1,5) I want to find out if there's a frame of reference where the events are simultaneous. I find the change vector X_b - X_a = (Δct,Δx,Δy,Δz) =...

Hello, The three clocks A, B and C is at rest in S frame. The clocks unsimultaneously change its frame from S to S'. The frame change events is simultaneous in S' frame. Now, clocks is moving in S frame and at rest in S' frame. I am struggling with this. The events on A clock displayed by...

Homework Statement When the box is at the bottom of the incline it will have a velocity of vf The person is an inertial frame of reference with a velocity of vf When the person starts moving, the box is moving backwards with the velocity of vf. This means at the top of the hill the box has...

We know that we can't say whether we are at rest or uniformly moving if we're in a einstein cage..but if the same medium is accelerating/decelerating can we being inside(and can't see outside) claim abt state of cage..?I ve read that a non-inertial can be converted to inertial by incorporating a...

The question: Suppose two identical particles, each with mass m and kinetic energy T, collide head-on. What is the kinetic energy of one in the rest system of the other? The solution: Is given on pg 109 of Griffiths' Introduction to Elementary Particles. Griffiths writes down the total...

Hi there, I am confused about the relationship between coordinate systems and reference frame in GR. I understand the coordinate systems can be used to describe reference frames, for example, Local inertial frames in GR can be defined by Riemann Normal Coordinates. However, take the...

Homework Statement An unstable particle called the pion has a mean lifetime of 25ns in its own rest frame. A beam of of pions travels through the lab with a speed of 0.60c. a) what is the mean lifetime of the pions as measured in the lab frame? b) how far does a pion travel ( as measured...

A charged particle is placed next to a current-carrying wire. The wire produces a magnetic field, but if the particle is at rest, the field exerts no force on it. However, in a different inertial reference frame moving at speed v parallel to the wire, the particle is seen to be in motion, and so...

I have just completed my class 10th. I was presently reading the class 11th H.C Verma physics textbook and here is what I confronted which seems to me as if I am unable to fathom : Now I can't understand that how come acceleration of book with respect to Earth isn't 0 ?! Please see bold part...

Suppose, a long object is at rest in S frame. There is A (On the long object) and B (Near the long object, on the ground) observer in the middle of the long object. There are two clocks located on both end of long object. We suppose, both A and B is at origin of S frame and clocks at some -x and...

Hi, This is partly inspired by the questions in the thread about normal forces on a cornering car but I thought I'd post here instead of mix that thread up with my question. So suppose we have a biker leaning into a corner. There are the normal force and the force of friction which act at the...

I have a Plot using Frame, and AxesOrigin set to a convenient value. The plot process offsets the physical origin of the Frame so that the specified AxesOrigin is just inside the Frame border - ie there is an offset introduced for both axes. Is there a way to tell Mathematica not to set any...

If we have light, any particle, and maybe car, the particles travel at 0.98c and car let say 50m/s. Let them start moving at the same time to the given point let say 300 metres away. The difference between times of arrival of light and particle will be small compared to that between light and...

Is it possible to have a center of momentum frame in a system with a photon and a massive particle? If you were to do so in a system with two massive particles, this would involve redefining the velocity of the particles in the CM frame. E.g. if A moves towards B with speed 2v, in the CM...

Homework Statement Two photons in the laboratory system have frequencies \nu_1 and \nu_2. The angle between the propagation directions is \theta. a) Write down the expressions for the total energy and momentum of the photons in the laboratory system. b) Find the photons’ frequency...