Inertial Definition and 500 Threads

Suppose we do a constant Jacobian transformation (which is not Lorentz) of a SR (inertial) frame, by using four linear change of variables equations. This defines an apparent field with a constant metric (which is not the SR metric) in which there is relative acceleration of separation. From...

I was just wondering what would the definition of the inertial frame be, since as I've understood the description it seems that an inertial frame seems to be 'free' from any external forces, correct me please if I'm wrong. Can something be an inertial frame even if gravity acts upon it? For...

it was mentioned in another thread that only inertial forces are frame dependent or relative. what is an inertial force? what are the differences between inertial and non-inertial forces? and most importantly: why inertial forces are frame dependent while other forces are not? i tried...

Homework Statement So I'm having some trouble understanding this paragraph from my textbook. I was hoping that maybe someone could explain it to me. For example, we can assume that the ground is an inertial frame provided we can neglect Earth's astronomical motions(such as its rotation)...

I was wondering how is our perception created according to relativity, since what we perceive depends on the perspective we have on the space-time around us. If two events are simultaneous in our frame by deduction from our perception we will realize that they are, and that the causal process...

Earth has a huge angular velocity regarding its rotation. Now let's imagine that the Earth has the velocity of 400 km/s relative to some inertial frame. What will be the velocity of Earth when we take the rotation into account combined with inertial motion? How do the 2 combine? Thanks in...

I've been working on a problem that I can't seem to get started on. Here is how it is posted: Metric of a space is: ds^2 = (1+2\phi^2)dt^2 - (1-2\phi)(dx^2+dy^2+dz^2), where |\phi | << 1 everywhere. Given a point (t_0 , x_0 , y_0, z_0) find a coordinate transformation to a locally...

Hello, Lately I have been wondering about the implications of the speed of light being constant for all observers, to me this seems to imply that there are different versions of reality for different observers. I will use a scenario to illustrate my reasoning. After you read this I would like...

The question is to rank the inertial forces, euler,coriolis and centrifugal in increasing order of strength, for a observer in the Earth' rotating frame, observing a body stationary in the UK. My thoughts are that coriolis = 2mw X (dr/dt), and so depends on the velocity so can only come into...

Hi, I have been reading about CERN for a while and found amazing - amongst many other things - the fact that hadrons in the LHC turn some of their energy to mass after having reached the maximum possible speed. However this statement was not clear enough. I was wondering whether the mass they...

Does inertial motion (understood in the SR sense) exist in a curved spacetime?

https://www.youtube.com/watch?v=1VW1y6isl18 Above is an old video of a double inclined pendulum device producing unidirectional motion. Here is a newer but much cruder replication https://www.youtube.com/watch?v=N-JKa4Bexz0 Physicists however put Inertial propulsion in the same...

Hello all, my question is related to graduate school topics and future postdoc possiblities. I'm a double major in electrical engineering and physics and have been doing plasma physics research as an undergraduate for roughly the last two years, with the last summer I played a part in...

Hi all, think this might be a silly or trivial question but I've got myself in a bother so thought I'd get some help. Best to illustrate my question with an example. Take a vector expressed in some chart, then we can find the components of that vector in another chart in the standard way by...

Homework Statement A pendulum is placed on a rotating platform which rotates with angular velocity ω around an axis, at equilibrium the angle between vertical and pendulum is θ θ= 20 degrees ω= 10 1/s how far is the pendulum placed from the axis Homework Equations...

Homework Statement a) A light-source at rest in an inertial system S' is emitting light with angle θ' relative to the x'-axis. The System S' is moving at speed v (along the x-axis) relative to the laboratory system S. Show that the emitted light is making an angle θ with the x-axis of...

My mechanics prof today said when setting GMm/r2 = ma, the canceling of the small m is actually a bit nuanced because you have to assume the gravitational mass is equal to the inertial mass (though it's supported by experiments). I'm so used to seeing mass as just mass so I'm having a bit of...

Quick disclosure, I'm only a few weeks into modern physics, and still trying to get a firm grip on the mechanics involved here. My understanding is that it is possible to use a reference frame that is moving, and this leads to a bit of a paradox, at least under certain conditions. Take two...

Newton's laws of motions are not applicable in Non-inertial frames of reference which means only mutually accelerated frames of references, My question is how can we apply Newton's laws of motions for practical experiments such as simple pendulum, motion of a ball, etc. conducted in near surface...

The title might be confusing. Anyway while preparing for a seminar I made a statement, " Absolute space does not explain the inertial forces, since they are related to acceleration with respect to anyone of the inertial frame". Is this statement correct? Please explain with few examples, Thank you..

Hi guys, I was reading some stuff about general relativity and the first impression is that isn't completely the follow-up to SR. In what I've read it has a different assumption about inertial frames, that they are only significant only locally. What does this really mean and what are the...

Homework Statement I have been solving problems on my own and I came out with a problem I made up myself. It's simple: There's a triangular big block of mass M with an angle of \theta and on top of it there's a rectangular block of mass m. See figure attached. When the triangular block is...

According to QM the ground state of the quantized empty space is not considered to be empty but as a fluctuating sea of virtual particles creating and annihilating continuously. In the case of virtual particles with mass I have a problem with this. According to which reference inertial frame are...

Suppose that two events occur on the x-axis of an inertial frame, Δx apart with a time interval between the events of Δt. a) the proper time interval between the events is...? b) the proper distance between the events is...? I think I'm just getting confused by the wording. I imagined that...

Homework Statement A bug of inertia m_B collides with the windshield of a Mack truck of inertia m_T \gg m_B at an instant when the relative velocity of the two is \boldsymbol v_{BT}. (a) Express the system momentum in the truck’s reference frame, then transform that expression to the bug’s...

Do we measure different frequencies of light in frames moving relatively at constant velocities? Because when we look at an annihilation reaction from the view of different frames, we see different energies of the reactants which seem to affect the frequency of the produced photons. your kind...

I can't seem to get my head around the difference between the two. Inertial mass appears in F=ma and is a measure of an object's resistance to acceleration when being acted upom by a force/s. Gravitational mass appears in F=(GmM)/r^2 - what 'role' does mass play here?

Hey everyone, I started reading up on GR a couple of days ago, and I'm somewhat stuck on the concept of a free-falling IRF. I understand that an observer on a free-falling small spaceship would experience the laws of physics in a rather simple form, eliminating the need for a force of gravity...

Homework Statement ds^2 = g_{tt} dt^2 + g_{tx} (dt dx + dx dt) with g_{tt} = -x and g_{tx} = 3 "Show that this is indeed a spacetime, in the sense that at every point, in any coordinates, the matrix g_{\mu \nu} can be diagonalized with one positive and one negative entry. Hint: You...

There is something that bugs me about inertial frames. According to Einstein's definition (chapter 4 of "Relativity"), an inertial frame is one for which Newton's first law holds: "a body far enough removed from other bodies continues in a state of rest or uniform motion in a straight line." He...

I just confused myself with this idea, need someone to fix it please! Say a spherical black body temperature T is moving with velocity v in some direction through some medium with a lower temperature. In the sphere's rest frame this emission is isotropic, however, in the rest frame of the...

Is it ok to formulate the postulates of SR like so: 1) If two reference frames are in a constant rectilinear motion relative to one another, then the laws of physics take the same form in both of them. 2) If two reference frames are in a constant rectilinear motion relative to one another...

You are conducting an experiment inside a train car that may move along level rail tracks. A load is hung from the ceiling on a string. The load is not swinging, and the string is observed to make a constant angle of with the horizontal. No other forces are acting on the load. Which of the...

Apologies if this is in a FAQ somewhere. A is out in deep space. B is falling toward the planet. Does A need both SR & GR to calculate B's time/space dilation as determine by A's IRF?

Can anyone refer me to a discussion of applying the technique of changing reference frames to problem solving? Why it works, and what it means. I'm familiar with using it in some E&M problems, but I guess I don't really "get" it. For example a particle in an E&M field has m\vec{a} =...

The most common definition of mass, at least in the Newtonian context, is in terms of a measure of inertia: The mass of an object is a measure of, and gives rise to, its resistance to changes in motion. F=MA presumably quantifies this idea of inertial mass. I'm wondering whether any...

How do we mathematically define a inertial frame in GR? Is it only a basis in some tangentspace or does it have to be induced by a coordinatechart? :/

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...

Homework Statement I was given a sample of 5000 points from an ellipsoidal blob (in 3D) that has some orientation. Assuming that each point has equal mass, I was asked to calculate the inertia tensor of this blob, then find the principal axes to determine the orientation of this blob...

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 ...

What is an inertial reference frame?How are positions,velocities and accelerations changed when switching between different inertial reference frames? r=rx i + ry j + rz k Inertial reference frame:It is a frame of reference where Newton's laws of motion is valid.No fictitious...

hello, in relativity something can go faster than the speed of light as long as it is not in the observer's frame of reference which would say that a FOR has a size but i read that a FOR was infinite in all directions. Someone explain this contradiction please!

Assuming $$\vec{r_{a}}$$ and $$\vec{r_{b}}$$ is calculated from an inertial frame of reference. then for any two objects (named a and b) in a system of more than two objects, Is this the Newton's third law, $$\frac{d^{2}}{dt^{2}}m_{a}\vec{r_{a}}=-\frac{d^{2}}{dt^{2}}m_{b}\vec{r_{b}}$$...

can inertial reference frame ever have "lenght contractions" in 3d or in rest? hi! thank you for all answers in this topic in previous threatin same topic. i open this new thread in same topic but here i try to keep the issue here very short and readable , with no speculation and concentrating...

Homework Statement Homework Equations Frotating = Finertial + Fcor + Fcf The Attempt at a Solution For the inertial field: F = -qv x b -kQq/r2 For the rotating field it would be the same term plus the coriolis and centrifugal forces. The issue I'm having trouble with is this: The v...

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...

Reynolds numbers and "inertial force" I am an undergrad physics major taking an engineering course that just introduced the concept of reynolds numbers. When I try to get an idea of how the Reynolds number is physically derived, I keep running into the definition that it is the "ratio of...

Hello everyone, this is my first question here. I'm a mathematics student (actually pure math), but have recently found myself interested in learning about physics. I've started reading Introduction of Special Relativity by Rindler; I actually have no background in mechanics or basic physics...

Hi, In the classical theory, there is an absolute rest frame, and every frame moving with constant velocity with respect to it is called inertial frame of reference. The frames that are accelerating with respect to it are called non inertial. To test whether a frame is an inertial, we test...