Frames Definition and 610 Threads

Dear experts, What software is available (free or not) to optimise the member cross-sections of trusses or frames? Which one is your favorite? Would any of them optimise the topology and geometry? Ideally, the global buckling of the whole structure as well as the buckling and strength of...

I want to know why an else solution can not get the right answer. And want to know the way to correct this solution.Supposed that a frame S'' is moving in the lab frame at ##\beta_x## in the x-direction, ##\beta_y## in the y-direction, now I want to find out the Lorentz transformation between...

A particle is moving in the lab frame ##S'## at ##\beta'_z##. I want to transform coordinates and momenta of the particle to a frame ##S## moving at ##\beta_0##. At time ##t = t' = 0##: $$z = \frac{z'} { \gamma_0 (1 - \beta'_z \beta_0) },\, \gamma\beta_z = \gamma_0 ( \gamma'\beta'_z -...

Which ways are available to know how two frames are connected? I mean, to know how they are related to one another?

I have a really stupid question. Suppose I am in a car and the car is going around a loop. Yes, the Earth is not inertial -- it rotates -- but let me ignore that and, momentarily, designate the Earth as inertial. Now, we know the frame of the car is not inertial--the car is turning. We...

I will refer to the example given in 'On the electrodynamics of moving bodies' concerning a rod moving in a coordinate system, in which a beam of light is sent from one end of the rod to the other and is then reflected back. Usually when calculating relative velocities, we may simply consider...

These quantities are evidently not equal unless v1 = v2, but surely the change in kinetic energy should be the same in different frames of reference? I was wondering what mistake or misconception I have made because this has been bugging me for a little while. Thank you in advance!

Lets neglect conservation of momentum and assume that all frames of reference are inertial. Now imagine three objects: the sun, the Earth and an asteroid. In the inertial frame of the sun, Earth and asteroid are flying towards each other ( velocitys v and -v). Now imagine you are standing at...

Ok, this is the notation I am going to use in this thread: uppercase means vectors, while "[V]c" means coordinates of vector V in frame c. I'm reading from a book: i have a reference frame "a" and a reference frame "b" rotated with respect to "a", the vector connecting the frames origin is R. We...

I am studying the fact that two events that are simultaneous in a frame aren't (in general) simultaneous in another. The lamp is equidistant from the two ends. When the light is switched on an observer on the train sees how both light rays hit the back and the front of the train...

Hi, Could you please help me to clarify the following problem? In the gravitational field of a mass, the force on a body in steady state comes from the gradient of the gravitational potential - or the gradient of speed of time. But what about accelerated reference frames? I assume that there is...

The attempt is above

Hello Is it even possible to have an answer for D given condition #4 ? i need help in just for question D, and not everything else . Thanks :] The Attempt at a Solution Because Either S or S' Could be accelerating, and depending on which one and how much is accelerating, there will be different...

Hi everyone. Please be gentle with me, I am not a physicist! I am a layperson with an interest in learning more, and I’m reading a book called ‘How to Teach Relativity to Your Dog’ by Chad Orzel. It’s supposed to be physics for dummies, but it’s clearly not dumbed down enough for me because...

The term "Lorentz transformations" only refers to transformations between inertial frames. However, if we differentiate velocity with respect to time, we obtain acceleration. The Lorentz factor says: t(0 reference frame observer at rest) / t(moving) = 1 / Sqrt[1–(v/c)^2] t0 / tm =...

Peeling this out into its own thread for clarity: How is time dilation of extreme reference frames (photons, black holes, intergalactic space-time) taken into account in Big Bang cosmology? Since from the POV of a singularity or a photon, their clocks have effectively stopped and any lower...

In several special relativity textbooks, I have read that special relativity only deals with observations made in inertial frames, and that it makes no predictions about observations made in non-inertial frames, and that only general relativity deals with non-inertial frames through the...

This question concerns inertial frames. I am aware that an inertial frame is one that is not accelerating. I am aware of an alternative definition: it is one on which no forces are applied. (Yes, they are the same thing.) I am also aware of the d'Alembert "forces" that appear when a frame is...

Homework Statement Two images are attached. The first image details the problem. The second image has an x',y' coordinate system depiction of the problem. Homework Equations The total energy of a particle is defined as E = mc^2, with m = γ*m_0. The Attempt at a Solution If the x', y'...

Homework Statement I am having a issue relating part of this question to the Galilean transformation. Question Relative to the laboratory, a rod of rest length ##l_0## moves in its own line with velocity u. A particle moves in the same line with equal and opposite velocity . How long dose it...

I know that special relativity is based on the postulate that an object that travels at the speed of light with respect to one inertial observer must travel with the speed of light with respect to all inertial observers. This postulate implies that no two inertial frames can differ by a relative...

According to special relativity, all inertial frames of reference are equivalent for descriptions of physical phenomena. Suppose that there is a free particle in free space. Observed in any of the frames, the motion of particle can be described by a velocity, and by Lorentz boost, one can get...

My question is about some physical quantities which two observers in two respective inertial frames will find the same. I wonder are there any such quantities? Some books say force, speed of light etc are constants for both the observers. Please guide me on this. Regards.

Homework Statement Which of these situations describes you observing from an inertial reference frame? a. you are in the car of a train, seated at a table, and the train suddenly slows down b. you are in the car of a train, going north, and the train goes around a curve to go west c. you are in...

Do you really need to absorb an advanced paper to answer the question? Let's view the problem this way: The ship is traveling at a constant .999c relative to Earth just prior to reaching Earth The ship puts on the brakes moments before reaching Earth, so that it is now at rest relative to Earth...

Homework Statement This is the problem. A pair of eyeglass frames is made of epoxy plastic. At room temperature (20.0°C), the frames have circular lens holes 2.20 cm in radius. To what temperature must the frames be heated if lenses 2.21 cm in radius are to be inserted in them? The average...

I am not a physicist—not even close—just a guy who, for some crazy reason, decided to try to understand some of the basics of relativity. I’d like to understand them well enough to be able to explain them (correctly) to another lay person. I’m trying to see how much I could explain without...

I have a question If an object is traveling at a certain speed and 1 sec in our time is equivalent to 100 sec in the objects frame of reference. Then how fast is the object traveling??

Homework Statement Imagine there exists reference two frames, a frame O which is stationary and another, O' moving relative to O. If there is a four vector A--> (A0,A1,A2,A3). Then why is Aae->a as measured by the observer O equal to Aa'e->a' as measured by the observer O'? The components are...

Hey everyone, I've been researching for some time now, and I can' find anything about how the actual lens blanks for prescription eyeglass lenses are made, I've looked on websites like this: http://glassescrafter.com/information/how-prescription-glasses-are-made.html but it only explains how the...

I am reading through a textbook on AP Physics, and I came across a few references to non-inertial frames of reference. It doesn't clearly say what a non-inertial frame of reference is. Based on the examples it gives, I assume that it is a frame of reference where the observer is experiencing...

Hi, I am trying to gain insight into using stationary vs. rotating coordinate frames for natural frequency calculations. I have seen many FE codes suggest that critical frequencies can be calculated differently in rotating and inertial frames, so i wanted to do a 1D calc to see for myself how...

Homework Statement Imagine that you are flying on an airliner on a long flight to Europe, at a constant speed of 300 m/s. a) You throw a ball towards the back of the plane at 20 m/s. You then shine a beam of light towards the back of the plane. How will these two things—the ball and the...

So I learned from the first few posts on this https://www.physicsforums.com/threads/ftl-train-ftl-communication-thought-experiment.945116/ thread that one can actually work with special relativity in non inertial frames. I'd like to get some points on this. Firstly, by a non inertial frame, I...

I'm aware that there are definitions of how reference frames translates to mathematics. But I've came to the following. How incomplete would be to say that, mathematically speaking, two Lorentz (or whatever) inertial frames are two subspaces of a given vector space whose span is the same vector...

Homework Statement 1. Two skateboarders start from rest on opposite sides of a ramp like the one in the image, roll down and collide elastically on the level part of the ramp. The masses of the skateboarders are m1 = 48 kg and m2 = 55 kg and they both start from the height h = 4.70m. Ignoring...

Homework Statement My professor gave us a werid question which is as follows In the laboratory frame, two clocks are synchronized and measure two light sources at the same time situated at 3 years in time axis and 3 light years and 2 light years in x-axis >At what velocity is the frame ##S'##...

I know this is a naive question that has almost certainly been brought up numerous times before, but my search abilities seem not to be sufficient for finding a good answer, so if anyone just refers me, that would be fine. The question: Special relativity concerns comparisons between pairs of...

Suppose we have a rotating frictionless disk and there is a rotating observer on the center of it. Furthermore, suppose a very small ball on the disk's edge. Now we clearly know that the ball is not moving but the rotating observer sees the ball following a circular path with an angular velocity...

One particular form of the equivalence principle states that The laws of physics for freely falling particles in a gravitational field are locally indistinguishable from those in a uniformly accelerating frame in Minkowski spacetime My question is, does one arrive at this conclusion from a...

Suppose a person A is standing in a bus and bus is accelerating forward then when a person B standing outside observes A he see that A is accelerating in forward direction then there must be a force acting on him which is making him accelarating(because Newtons first law holds in Earth's frame)...

To what extent is the Heisenburg Uncertainty principle a statement about moving frames of reference? The ill-defined position of a particle seems to imply that one can never find an inertial frame of reference in which the velocity of a given particle is constant.

Let's assume that a and b charges are moving. now in our lab frame there will be a electric+magnetic force whereas in a rest frame of either of the charges, there will be only an electric force. So, two inertial observers will measure different forces?

Homework Statement A) Use Euler's equations to solve for the precession rate of a rapidly spinning gyroscope precessing uniformly (no nutation). Use I3 for the moment along the z axis along the axle. Beginning with Euler's equations, derive the coupled equations: ## \dot ω_1 + Ω ω_2 = \frac...

Hi, Could someone please have a look at my solution and let me know if I did it correctly. Thank you! 1. Homework Statement A pilot is flying from City A to City B which is 300 km [NW]. If the plane will encounter a constant wind of 80 km/h from the north and the schedule insists that he...

Homework Statement I'm trying to solve for this problem below.How would you be able to get the force in member ID and GC? Find the reaction forces in member AFGH Homework Equations ∑M = 0 ∑[F][/y] = 0 ∑[F][/x] = 0[/B] The Attempt at a Solution I dismembered all of its parts but no matter...

Homework Statement Homework EquationsThe Attempt at a Solution Distance between events w.r.t. Earth frame, De = | (1/2)w(t+Γ)2 - 350 - (1/2)wt2 | = 242 m Distance between events w.r.t. train frame, Dt =350 m , correct? As w.r.t. train frame , the train is not moving. But, a person on...

Homework Statement A child stands near the middle of a roundabout that is rotating with some angular velocity w. The child moves towards the edge of the roundabout in a straight line from the child's perspective and at constant speed. Explain in as much detail as you can (and using equations)...

Suppose I'm an observer out in space and 30 km from me there's another observer, who is static with respect to me. Let's say my name is A and the other is B. We're both far far away from all the cosmical objects that might have a gravitational influence on us. We both notice a spaceship flying...