Contraction Definition and 689 Threads

Homework Statement This is actually an exam problem, not a homework problem. The solution have been posted, but I don't understand the solution. Here is the question, as posted: A very long rod travels parallel and very close to a flat surface in our laboratory. The surface contains...

I was wondering whether or not the Earth would have a larger gravitational force, relative to me, if I passed the Earth at close to the speed of light? The reason I ask is if I pass the Earth by then it appears to be flatened, but only in the direction of its motion. So, if its length...

Is relativistic effect of length contraction physically "unreal"? One guru indicate that Length contraction has nothing to do with compression. It is more correct to view length contraction as a rotation in space time. If we rotate a box filled with gas or perfect fluid, clearly its density...

Homework Statement A spear moves past you at a very high speed. As it passes, you measure its length at one half its normal length. From this measurement, what can you conclude about the moving spear's mass? Homework Equations The Attempt at a Solution To have the spear appear...

The average lifetime of a muon is 2.2 microsec. What is the average distance the muon would travel in free space before decaying according to a stationary observer watching the muon travel with a speed of (.60c). I know how to find the proper time. 2.2/Sqrt[1-(.6c/c)^2] = 2.2/Sqrt[1-.6^2]...

It's a fact that a shaft in a turbine is expanding when the temperature is increasing. A simple equation gives that the expansion can be described as: deltaX=(T1-T0)*alpha*x0, where deltaX is the expansion, T0 is the initial temperature, T1 is the final temperature and alpha is a coefficient...

Homework Statement A rod of rest length L0 = 10.4 m moves with a speed v = 0.42c along the x axis. The rod makes an angle of q0 = 66.1° with respect to the x' axis (primed frame is moving with the rod). What is the length of the rod as measured by a stationary observer? Homework Equations...

Hello everybody, Thank you in advance for your help. I am trying to model thermal contraction of an elastic solid in Comsol. I am sure this is a simple model, but I am a new Comsol user and it is not obvious to me. My goal is to model the stresses within an elastic solid, that arise...

Homework Statement About how many femtometers shorter than its rest length is the length of a car measured in the ground frame if the car is traveling at 30 m/s in that frame? Assume for the sake of argument that the car's rest length is 5.0 m. Remember that 1 fm = 10^-15 m. Homework...

Hello there, a simple special relativity question, how can the Time Dilation and Length Contraction Formulas be derived from the Lorentz Transformation Equations?

In most special relativity primer book, length contraction section, the length is always defined or measured by the time of a light flashing at one end of a rod, traveling to the other end, reaching a mirror and reflecting back to the first end. Please read this example if I did not make...

Can someone please clear up the nature of length contraction Does the spatial dimension parallel to the motion of a moving metre stick contract (as seen by a stationary observer). Or Is contraction a purelly matter phenomenon whereby space is constant and the actual material of the...

I'm sure this question has been asked before, but I haven't been able to find a good answer using the search function. I have a differentiable manifold M and some coordinate chart. I have vector and covector fields on this manifold, but no metric. At some point P, I know I can write the...

Hi, I am having a hard time understanding the Lorentz - Fitzgerald contraction hypothesis (LFCH). I understand that it is a pre-relativity explanation of the null result of Michelson-Morley Experiment. My question is how did Lorentz derive the gamma factor, namely 1/sqrt(1-v^2/c^2), my...

http://home.orange.nl/kuip3148/phys1.JPG Not exactly homework, but a problem I found in my lecture notes. The train is moving at a constant speed 0.5c. Question b asks what the length of the train will be then at t = -1. From what I understand, this suggests that length contraction depends...

before I start, I should say that I'm a layman and as such will probably say something which sounds quite stupid to the rest of you. I will clarify anything that needs clarifying Ok, so we have A - a 2 light year long garage with two doors that can swing open and closed B - a 4 light year...

We're just learning special relativity in class and my lecturer uses the light clock argument (two moving clocks - one parallel and one perpendicular) to explain length contraction. I didn't quite get one thing about it. My notes say the light beam reflects at different times (i.e. they have...

I have two problems that I got confused with and I am not sure if I am doing right Homework Statement 1) The starship ENTERPRISE 1200m long when at rest. How long would it seem to be to someone watching the ship pass by them at 0.75c? Homework Equations length contraction \Delta...

If I am watching spherical mass A that is traveling away from me at close to light speeds it lorenz contracts like I am looking down at a plate. Does the distance mass A is from me contract also or does it stay the same distance away ?

Why would the Michelson-Morley experiment be the experiment which proves "length contractions" of measuring rods if everything within the experiment lie on the same frame of reference? According to Relativity, no contraction should exist at all in this case. If the mathematical...

on a vertical spring (k=100n/m) there is a box with a mass of 5kg, a ball of 1kg is dropped into it from a height of 1m what is the maximum contraction of the spring if the collosion is plastic. i hope that my terminology is correct as i am not studying this in english and am translating...

We could imagine a rod moving fast enough to compress it within its own Schwarzschild radius. Should it collapse into a black hole? Or is the rod's own reference frame, where it isn't compressed, the one that makes decisions here?

If an observer rotates a four dimensional object, the lengths of the object would change to the observer. If that same observer walks backwards, the lengths of the object will also appear to change from his frame. In fact, if either the observer or the object rotates or moves in any way, it will...

good night, this is not actually a homework question, this is just plain curiosity. we've written a basic problem on length contraction and tried to resolve it ourselves. we just want to know if the concept of the problem is right. Homework Statement a body of length L=20m travels...

Is relativistic effect of length contraction physically "real"? Is Lorentz contraction a real contraction? For example, if one tries to accelerate a solid body, does its contraction require an extra input of energy to squeeze the atoms of the body closer together? Will this extra energy go into...

Consider a train traveling at a relativistic velocity, with three observers. One inside the train, and two outside the train traveling at different velocities with respect to it. Say there is a finish line of sorts at a certain point. All observers will agree when the train reaches the line...

A stick of 1m in length travels at v = 1/2 c along its axis away from the observer. Question 1: Show that the observer perceives the length of the stick to be shorter without theory of relativity. Calculate the length as perceived by him if he calculates it by the difference in length...

There's one of the paradoxes with SR that I've never actually seen an answer for. There is a man on a train traveling at a velocity where length contraction starts to matter. Say, .3c. There are some dirty bandits that have rigged up a trap door system in a mountain up ahead on the tracks...

Hi guys, There's a couple questions that I've been trying to figure out that I have not been able to make much progress on. 1. Time Dilation the equation states that T' = Lorentz Factor * T0 So the Lorentz factor will always be > 1 because v < c So then, if, let's say, there's 2...

Please let me know if length contraction could be derived without using synchronized clocks. Thanks in advance.

Here is a simple question. How can an observer measure length (or length contraction) of a cylindrical Iron rod, when it is moving with a relative velocity v with respect to the observer? The reason to ask is not to inquire the math about it, but if the rod is moving say in x direction, from...

This is similar to the pole and barn paradox, but different enough that I'm not quite confident in my answer: A train and tunnel have the same length when at rest relative to each other. The train approaches the tunnel with constant velocity. An engineer on the train places rockets on the...

Hi i have just been given my physics coursework and wondered if anyone had any pointers or tips on how to answer? The question is on the expansion and contraction of wood with changes in temperature and humidity using a strain gauge. We have to explain how we would use lab equipment to...

[SOLVED] Help: Length Contraction and changing Frames Hi i have been learning about length contraction and i thought i understand how it works until i was given this question. A very fast train of proper length Lo rushes through a station which has a plaform of length L(<Lo). According to...

Homework Statement A bar (lo = 10mm) is moving along the x-axis with speed v according to a referential R. Meanwhile a table, parallel to the bar is moving along the z axis, with speed u. There's a circular hole in the table with radius = 5mm. From R perspective the bar has l < 10mm and it...

Hi, I am an undergraduate, doing an experiment regarding of minor losses due to sudden contraction. However, I found that my theoretical loss is higher than the experimental loss. The flow rate = 3.28*10^-4 (m^3/s) (Inner diameter) D1= 3.652*10^-2 m (Inner diameter) D2= 1.539*10^-2 m by...

Bear with me. I am a lawyer, not a physicist... I understand how the light clock demonstrates time dilation with special relativity. I think I understand length contraction. Here is my question: at relativistic speeds, why does length contraction not affect the distance traveled by the light...

I am not a physics student (my background is that of an engineer + MBA) but have read a lot about relativity and have built up a fair level of understanding. I just thought up a situation regarding Lorentz contraction that has kind of confused my understanding of the same. Consider the...

So I have been trying to wrap my head around time dilation and length contraction... It is all good until i come to the point to derive length contraction from time dilation... So we have \gamma \Delta \tau = \Delta t \gamma L = L_0 So now from my lecture notes i have an observer...

Hello, I recently learned of the Lorentz contraction and mass distortion effect in a physics book, and for the sheer heck of it, I decided to see what it would be like if my dog, Little Ann, were sped up to relativistic speeds. I decided to try to calculate it using the equations provided by...

Problems on "Length contraction" Homework Statement This is a problem in my text. The idea is that a bar is moving with a high speed (say 0.5c) relative to us. We now want to know what will be the length appeared to us if the bar is parallel, perpendicular and 60 degrees tilted. And we are...

Homework Statement The gravitational potential energy W of a self-gravitating sphere of mass M and radius R depends on the detailed distribution of mass within the sphere, but it is generally of order of magnitude -GM^2/R. For the Sun, W_sun = -2G(M_sun)^2/R. What is the timescale t =...

Consider what happens when we accelerate a box filled with gas. We have to expend a certain amount of energy to accelerate the box, In Newtonian mechanics, this energy goes into the kinetic energy of the box: as its speed increases so does its kinetic energy. This happens in relativity too, of...

why does the einstein field tensor have the riemann tensor contracted? I am confused as to what purpose it serves. I have seen an explanation that it gets rid of extra information about spacetime or something like that. and also is the Ricci scalar added to einstein tensor so that the covariant...

Textbooks I know derive the formula that accounts for the time dilation by measuring simultaneously the space coordinates of a moving rod. Is there another way to derive it?

A rod of length 2l is at rest in frame O' with co-ords (x',y',z')=(±l,λ,0) Observer O moves at speed u along the x axis. The first part of the question is just to derive the length contraction - fine, O measures the length as 2l / γ The next part has me stuck: "Show that, at t = 0...

Please tell me if it is possible to derive the formula which accounts for the Lorentz contraction from the invariance of the space-time interval. Thanks

Consider some material object, more or less rigid, with two ends, A and B, like A---B It is at rest at a point in time t_0 in my reference frame. Now I kick it a bit, i.e. I apply some force for a limited amount of time at A in the direction of B. After the kick, the whole object has a...

De Sitter relativity and Lorentz contraction I need help in understanding the elements of a paper that I think could turn out to be quite important, namely http://arxiv.org/abs/0711.2274 de Sitter Relativity: a New Road to Quantum Gravity R. Aldrovandi, J. G. Pereira) Inter aliathey say...

Directly from the Peskin & Shroeder, page 63: S_F(x-y) = \int\frac{d^4p}{(2\pi)^4}\frac{i(\displaystyle{\not}p + m)}{p^2-m^2+i\epsilon} e^{-ip\cdot(x-y)} I'm slightly confused with the notation with the contractions. Things like \overline{\psi}(x)\psi(y) and \psi(x)\overline{\psi}(y) get...