Reference frame Definition and 227 Threads

I have some question about referance frame 1-Is physics works without referance frame ? 2-Is Space-time itself can be a referance frame ? I mean "Earth speed, relative to arbitary point in space time, is 100.000 km/s" Is this sentence make sense to physics ? Or we need an object to make a...

Homework Statement I am reviewing for my midterm and I just want to quickly understand a concept. It seems that velocity does not depend on the original reference frame. For example, let's say spider man is standing on the ground next to a 78.4 meter tall building, and it is known that if he...

I had a though last night that kept me awake trying to figure out what I was trying to understand. I have been out of school many years now so I have forgotten much.. Here is my question. Lets imagine there is a 30 meter diameter hole (complete with a vacuum) in my front yard that goes through...

Homework Statement An inclined plane, fixed to the inside of an elevator, makes a ## 32 ^\circ ## degree angle with the floor. A mass m slides on the plane without friction. What is its acceleration relative to the plane if the elevator accelerates upward at 0.50 g? Homework Equations...

At about 05.30, Dr. Lewin makes a small calculation to find the centripetal acceleration one experiences due to Earth's spin (at the equator). He then says that because of how small the magnitude of this acceleration is, we could consider the Earth's surface to be an inertial reference frame...

I've managed to get through all of this question without trouble until part d). The full question is given here: I've calculated the "true" angles of Star A and Star B as 71.57 degrees and 45 degrees respectively in Frame S, and the "light" angles should be the same, since the stars are...

Homework Statement Anna and Bob have identical meter sticks. Anna an observer on Earth, sees Bob traveling in a spaceship at 0.5c away from her. Bob leaves his spaceship in an escape pod, moving away from Earth and the spaceship at 0.1c with respect to the spaceship. How long is Bob's meter...

Hello, I noticed quite a few questions on the Hafele-Keating experiment here, but I believe none that have my exact question. I understand the explanation given for "a frame of reference at rest with respect to the center of the earth", as in the Wikipedia article. But what happens if...

Homework Statement I have attached the problem as a picture on this post, am really really unsure on how to start! so far the only thing i can think of doing is using this equation (\frac{d^{2}r}{dt^{2}})_{s} = ( \frac{d^{2}r}{dt^{2}})_{s'} + 2ω \times (\frac{dr}{dt})_{s'} + \dot{ω}...

So I was told that a pseudo-force acts on a body when its's motion is analysed with respect to a non inertial reference frame. I'm a bit confused. Does that mean the reference frame is accelerating with respect to the body, or with respect to the earth? And why does there have to be any sort of...

Homework Statement A uniform thin rod of length ##L## and mass ##M## is pivoted at one end. The pivot is attached to the top of a car accelerating at rate ##A##. What is the equilibrium value of the angle ##\theta## between the rod and the top of the car? Homework Equations None in...

In SR there is a whole family of so called inertial observers that are defined as those observers that move at relative constant speed with respect to one another, whose descriptions of nature are all equivalent and whose spacetime coordinate are related by Lorentz transformations i.e. those...

I red a classical mechanics concept in a book. Imagine that we have two observers with two frames of reference F1 and F2 observing a particle P in motion. One of the observer is in motion and another is at rest,(lets take F1 is at rest and F2 is in translation motion with velocity V) let r1 be...

"Proper Reference Frame"-Accelerated observer Hi guys. This is regarding section 13.6 (p.327) in MTW. Here the authors consider an arbitrary accelerated observer in any space-time and construct a set of local coordinates carried along the entire worldline of the oberver with the origin of the...

Each VSC station has the same configuration, and its vectorbased equivalent circuit in the synchronous dq reference frame is shown in Fig. 1(b). Could someone please explain me what doe "dq reference frame" mean?

Homework Statement A disk rotates with angular velocity ω. It has a groove cut along the diameter in which two blocks of mass m and M slide without friction. They are connected by a light string of length l, fixed by a catch with block m a distance r from the center (r + radius of M = l)...

Hi all, I have a question about how to analyze the problem of a ball rolling down an incline plane. Assuming there is friction, at each instant the ball swivels about a pivot point on the incline that is stationary due to static friction. We then would analyze the torques about this point...

I have two rigid bodies floating in space that are kinematically constrained by a joint (think of a 2 dof link mechanism floating in space). I have a body fixed reference frame on each rigid body plus the global space-fixed reference frame. The first rigid body is in the space-fixed...

I'm attempting to build a line follower robot and I'm currently in the process of building appropriate models. For the control system I need to define a coordinate system. The most convinient coordinate system from many point of views would be a coordinate system that moves along and changes...

Homework Statement Imagine that a circular disc is rotating with a frictionless ball on it( ball is not at center of the disc) If we observe the motion of the ball from the rotating frame of reference, then how can we describe its motion? Homework Equations The Attempt at a...

for the 1st two I used v is to the reference frame = 37m/s- -35m/s=72m/s a)ball=[(m2-m1)/(m1+m2)]v bat=v2=[(2m1)/(m1+m2)]*v b) I do not know how to solve for part b. The Attempt at a Solution

So I would agree that it has a uniform tangential velocity but would the centripetal acceleration of the Earth put it in a non inertial frame.

Time in the "reference frame" of the photon and as well curved spac Hi there! I understand the tendency of physicists to stick to the math, and the logic itself, and to often avoid attempting to conceptualize a process or law, but that's kinda the opposite of what I'd like to do here. I...

Why can we not CHOOSE a reference frame locally and treat everything inside of it as an inertial reference frame. For example in a classroom, the classroom is moving with the Earth and so is a ball rolling down the class. Because they are both equally moving due to the Earth's rotation, why...

Hi. I was recently calculating some centroids and I was wondering if the point were I choose my origin affects the centroid position. I.e., if I choose my origin at a massive particle, will the centroid be the same as with any other reference frame? Thansk :)

Due to my job and other classes, I've been studying ahead of my class by myself to not fall behind and I'm not sure if I'm oversimplifying this in my head and not really grasping the idea. Newton's First Law of Motion states that an object with a net force of zero stays in constant motion (or...

hi guys, i have a basic question on special relativity.. if the inertial reference frame denotes the frames that holds up the Newtonian 1st law, then can Earth be an inertial frame? i mean it changes direction of velocity as it moves in the orbit around sun, so its not in constant velocity ...

We have a problem of perfect reference frames( according what we are taught in school) If universe is expanding, the so called fixed stars are also moving. According to the special relativity, the speed of light is constant in every reference frame, So if we let light as the perfect reference...

hi can inertial reference frame be in different sizes at least in theory? i mean that can there be two different frames of reference in same place at same time, where the observer in both frames observes physical laws to be normal in their own frame of reference, but the other frame appears to...

Homework Statement In a given reference frame, event 1 occurs at t1 = 0 s and position x1 = 0 m while event 2 occurs at t2 = 3.6 × 10^−4 s and x2 = 0.60 × 10^5m. Is there a second reference frame in which these events could be at the same place but different times? If so, specify its motion...

Recently learned about Special Relativity, so my brain is running perpetual circles around itself asking questions. So, I figured I would come here and ask where could I find out more information about the Lorentz Factor being undefined at a luminal velocity? Or more basically, where do I...

Homework Statement If you are in a noninertial reference frame, that means: Homework Equations The Attempt at a Solution I know that nonintertial reference frame is something that is moving. However, if I am in it, then should I be moving together with it?

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...

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...

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...

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...

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?

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...

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...

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...

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...

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...

Hey guys, I am having some problems with the concept of inertial/non-inertial frames of reference and their applications in engineering dynamics. So I've learned that a given frame of reference is defined to be non-inertial when something in the studied system can only be explained through...

According to this, if someone spins around at 2 revs per second when the moon is in the horizon, the moon seems to move at 4 times the speed of light. And this implies the moon is not in our local reference frame. And per this, local inertial frame applies to "small regions of a gravitational...

Homework Statement The electron is traveling at a speed of β=.9999999, γ=1957, with mass mc^2=.51099 MeV. The Proton is traveling at a speed of β=.9, γ=2.29, with mass mc^2=938.27 MeV. They are heading in opposite directions, directly towards each other on the x-axis Find the reference...

If you a mass being accelerated by a force which is acting upon a spring attached to the mass it will exhibit harmonic motion. However unlike a fixed harmonic oscillator there is no explicit solution to the equation which describes the motion of the mass in a reference frame outside of the...

Can someone give me a clue/hint to finish this question? "In a reference frame S, the electric and magnetic fields of an electromagnetic wave E and B are perpendicular to each other. Determine the velocity of a reference frame S' in which (a) E' = 0 and (b) B' = 0"

Is this correct? There are two clocks on Earth that are synchronized. One clock goes out on a spaceship at .8c. Now according to the stationary or Earth FOR one year goes by for its clock but he sees that only .6 of a year has gone by on the clock of the spaceship. Now the spaceship...

So what will it see it self as?? At rest or moving a velocity c? Either way it seems to be a contradiction, so does that mean a photon can't be reference frame?