# What is Relativistic kinematics: Definition and 25 Discussions

The relativistic Doppler effect is the change in frequency (and wavelength) of light, caused by the relative motion of the source and the observer (as in the classical Doppler effect), when taking into account effects described by the special theory of relativity.
The relativistic Doppler effect is different from the non-relativistic Doppler effect as the equations include the time dilation effect of special relativity and do not involve the medium of propagation as a reference point. They describe the total difference in observed frequencies and possess the required Lorentz symmetry.
Astronomers know of three sources of redshift/blueshift: Doppler shifts; gravitational redshifts (due to light exiting a gravitational field); and cosmological expansion (where space itself stretches). This article concerns itself only with Doppler shifts.

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1. ### I Understanding Relativity of Simultaneity in Resnick, Part I

I'm going to go step-by-step through the reasoning. If there is any mistake, then it is a true mistake because I am trying to make each statement that follows as accurate as I can. Unambiguous time scale in a single frame of reference. Consider that we have two inertial frames of reference, 1...

7. ### Scattering angle in relativistic kinematics

Homework Statement Considering 2 scattering particles with momenta ##p_{1}, p_{2}##, where ##p_{2} = 0## in the Lab reference. The momenta of these 2 particles after elastic collision are ##p_{1}', p_{2}'##, respectively. Due to the 4-momentum relation, we have ##p_{1i}p_{1}^{'i} = e_{1}e_{1}'...
8. ### I Relativistic Energy Dispersion Relation: Explained

I'm in the process of learning special relativity (SR), and I'm a bit confused as to why the relativistic energy dispersion relation ##E^{2}=m^{2}c^{4}+p^{2}c^{2}## gives the energy for a free particle? I get that it is the sum of (relativistic) kinetic energy plus the rest mass term (a...
9. ### Special relativity - inverse Compton scattering

Homework Statement In the inverse Compton scattering there is a particle, with energy ##E## in the laboratory frame and mass at rest ##m##, which collide head on with a photon with energy ##E_\gamma##. Finding the maximum energy the photon can have after being scattered. The Attempt at a...
10. ### Special relativity - scattering angle

Homework Statement Finding the maximum scattering angle of a particle whose mass in ##m_1## which hits with relativistic velocity ##v## a particle at rest with mass ##m_2<m_1##. The Attempt at a Solution I've written the 4-momenta (p before the collision, k after the collision and the z-axis...
11. ### I Exploring the Effects of Relativistic Angular Velocity on a Rotating Disk

Let's assume that a disk is rotating with relativistic speed in a frame. We can find the velocity of a particle using v=rw formula. However, what is the r in this formula? is it the radius of the disk in rest frame or in the lab frame?? And Is the magnitude of velocity same for all points of...
12. ### How Do You Calculate the Original Mass in a Relativistic Disintegration Problem?

Homework Statement A body at rest in a frame of reference S disintegrates into two pieces moving in opposite directions. The masses of each fragment are 3.0kg and 4.0kg and their velocities 0.8c and 0.6c, respectively. Find the mass of the body before it disintegrated. (Answer: 10kg) Homework...
13. ### Beta+ meson, decay - Relativistic kinematics

Homework Statement The ##B^+## meson decays through the weak interaction. One of its decay channels is . If a ##B^+## is traveling with a total energy of 9.90 GeV, calculate the range of possible energies the produced may have. (i.e. determine the minimum and maximum values of its energy.)...
14. ### Relativistic kinematics: when will a photon and spaceship meet?

Hello to everyone! I cane across this problem and since I have no training in SR I can't solve it on my own, That is why I would very mutch apprecitate any help I could get. The problem: A photon and a spaceship simultaneously start at planet A and the travel in paralal towards planet B. The...
15. ### Relativistic Kinematics conservation of energy

Homework Statement A particle with rest mass m_{0} and kinetic energy 3m_{0}c^{2} makes a completely inelastic collision with a stationary particle of rest mass 2m_{0}. What are the velocity and rest mass of the composite particle? Homework Equations T = (\gamma - 1)m_{0}c^{2} = E -...
16. ### Relativistic Kinematics questions

Homework Statement The Attempt at a Solution So I don't know where I am supposed to go after I right down the energy conservation equation
17. ### What is the equation for finding the energy of a photon in a Σ0 decay?

Homework Statement The sigma Baryon Σ0 is at rest and decays to form an Λ0 and a ɣ photon. Homework Equations Mass of Σ0 is 1193 MeV/c^2 Mass of Λ0 is 1116 MeV/C^2 The Attempt at a Solution K obviously since the Σ0 is at rest, momentum must be conserved and the Λ0 and ɣ go...
18. ### Answer: What is the angle \alpha in B's frame with relativistic kinematics?

http://img842.imageshack.us/img842/9193/38076308.jpg Uploaded with ImageShack.us Homework Statement The velocity of B w.r.t A is: \vec{v}=0.6c\left ( \frac{\hat{x}-\hat{y}}{\sqrt{2}} \right ). what is \alpha (the 90 degrees of the triangle in A's frame) in B's frame? 2. The...
19. ### Horrible relativistic kinematics problem

Hello my name is Unto I currently study Physics (it's my first year) at the University of Bristol in England. I first came here with a really horrible relativistic kinematics problem, but I got no answers and managed to solve it myself. However you seem like nice guys, and it's always...

Here is the question that i am struggling with. A motorist passes a red traffic-light (wavelength = 650 nm). The motorist’s velocity makes an angle theta to the direction of light from the traffic light. Write down in four- vector and matrix form the relationship between the four-momentum of...
21. ### Understanding Relativistic Kinematics for Proton-Photon Collisions: A Guide

Hi all, I would be very grateful if anyone would be willing to check my understanding of this stuff as it has been several years since I used it in undergrad calculations. If a proton and a photon collide head-on with known energies, then the energy in the center of mass frame will be...
22. ### How Fast Do Spaceships Appear to Each Other at 0.99c Relative Speed?

An observer sees two spaceships flying apart with speed 0.99c, what is the speed of one spaceship as viewed by the other? the answer is: 0.99995c. well we have the equation of relative velocity: \frac{v_1+v_2}{1+\frac{v_1v_2}{c^2}}=0.99c now i think from the question that i need to find...
23. ### Relativistic Kinematics Problem

I've done a countless number of these problems before, so I was quite annoyed when I was unable to do this one. It's from Griffiths' Intro to Elementary Particles. Homework Statement A pion traveling at speed v decays into a muon and a neutrino, \pi^- \rightarrow \mu^- + \bar{\nu}_\mu If...
24. ### How Does Light Reflect from a Moving Rocket?

A rocket approaches a mirror on the ground at a speed of 0.90c. The distance D between the front of the rocket and the mirror is 2.4 * 10^12 m, as measured by ground observers, when a light signal is sent from the front of teh rocket. When is the reflected signal received by the rocket as...
25. ### What Is Relativistic Kinematics?

Anyone knows what it is "Relativistic Kinematics"? Please give me some "introduction"," History" " Reference website"..I don't know how to approach this topic? I need to write a paper about it? Frustrated!