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A specific reference frame that describes its coordinates in a manner that does not depend on time and is isotropic.

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3answers
95 views

Problem in understanding energy-mass equivalence

From whatever approach (either from modern approach by Hamiltonian or from Einstein's original approach by considering momentum), we can derive that $p_{i} = \gamma mv_{i}$ and $$H = \gamma mc^2 = \...
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1answer
35 views

Large Lorentz Boost

I understand the general concept of a lorentz transformation and a lorentz boost. What does it mean for a lorentz boost to be large however? My current guess is that this is referring to a large ...
6
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3answers
100 views

Electric car in different inertial frames

Assume there are two inertial frames $A$ and $B$ where $B$ is moving with speed $v$ relative to $A$. Suppose an electric car is stationary in frame $A$. The car is accelerated to speed $v$ to be ...
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2answers
71 views

Can we deduce the principle of relativity from some more basic principles?

I was reading "Relativity" by Albert Einstein. In chapter 5 page 14, it is written that If K is a Galilean co-ordinate system, then every other co-ordinate system K' is a Galileian one, when, in ...
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1answer
54 views

Does the space and time wraping depends on the relative velocity of frame of reference? [closed]

why i am asking this question is that, i thought that photon takes no time to reach the earth or any other place in the universe due to length contraction. the reason for this is space wraps completly ...
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0answers
64 views

Discrete structure of moving light in space-time. Does the light actually moving or it is triggered by cells of space-time? [duplicate]

I have an idea that seems for me interesting and exotic. It is not about a traveling with speed of light or observing a frozen light. Rather it is about the nature of light/photons and discrete ...
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0answers
46 views

Is the change in kinetic energy of a system the same in all frames of reference in Newtonian Physics?

I learned in Grade 11 Physics that energy is conserved. That fact depends on the truth of the following fact. For any system of objects, if its mass and momentum remain unchanged in one frame of ...
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4answers
148 views

Relative motion and time

When someone reaches to a speed which is close to the speed of light with respect to earth, will he see the things actually moving faster than when he is in low speeds?
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2answers
65 views

Postulates of Special Relativity

I have two questions about SR postulates. So first question, I heard two formulations of first postulate: "If a system of coordinates K is chosen so that, in relation to it, physical laws hold ...
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1answer
65 views

Lorentz Transformation Exercise confusion

So there is this very simple situation in one of my exercices: In the earth's frame of reference a tree is at the origin and a pole is at $x=20$km. Lightning strikes at both the tree and the pole ...
2
votes
3answers
87 views

Significance (if any) of coordinates in GR

I've studied General relativity for some time now and Read a lot about it, but still I'm convinced I am missing (at least one of) the main point. Maybe the simplest way to put my question is: what ...
1
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3answers
92 views

Earth's rotation in an empty universe

I have read these questions: Is rotational motion relative to space? Rotation in an 'empty' universe None of these talk about whether we can and how we can determine rotation of Earth ...
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5answers
145 views

Explain rotation in empty space

I have a doubt, general one. If we place a rod in empty space and apply a force perpendicular to the rod at one end would the rod rotate like it does in real world? I think it wouldn't rotate ...
0
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0answers
28 views

Can someone explain how photons does not experience time and distance [duplicate]

Google search: Does light experience time? A: "Well, not for light. In fact, photons don't experience any time at all. ... From the perspective of a photon, there is no such thing as time. It's ...
0
votes
1answer
64 views

Total kinetic energy of two particle system

Please help me understand this equation : Total kinetic energy of two particle system = K.E. of system w.r.t. centre of mass + K.E. of centre of mass Here's the derivation from my book : The author ...
0
votes
1answer
98 views

How do photons travel in time? [duplicate]

How can particles such as photons travel in time if they do not have any mass? They are inseparable, so how can you have one but not the other?
0
votes
1answer
45 views

How is Einstein's postulate about the invariance of the laws of physics justified? [duplicate]

According to one of Einstein's postulates related to special relativity, > "the laws of physics remain invariant in their form and nature in all inertial frames". But global inertial frames don't ...
0
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1answer
41 views

Addition of velocities

Let's say a car ,in straight line motion ,has a speed of V m/s (in the absence of wind) and let the speed of wind be W m/s the in the same direction . What is the speed of the car in the presence of ...
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4answers
114 views

What is the proof that the speed of light in vacuum is independent of relative motion? [duplicate]

Most people know that the speed of light in vacuum is independent of relative motion but I want to know the proof of it.
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0answers
56 views

Confusion about expression for length contraction of rod [closed]

My physics book states that in the construction in the figure, if the event C has coordinates x'= 0 and t' = l in the primed frame, then event C has x -coordinate in the unprimed frame: $$x_C = \...
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1answer
75 views

What happens if the moving frame in special relativity is non-inertial?

We have the lorentz transformation equations for relating inertial frame of references. What will the transformation equations be if the frames are non inertial? Is there any "pseudo-force like ...
11
votes
7answers
496 views

Is the second postulate of Einstein's special relativity an axiom? [closed]

I'm trying to grasp Einstein's special relativity theory and can't seem to find a clear answer as to why Einstein concluded that the speed of light is constant to observers in different inertial ...
2
votes
1answer
85 views

Is there a natural way to define relative wavefunctions?

Suppose I have two free-particles $A,B$ whose positions evolve according to wave functions $\psi_A(x,t)$ and $\psi_B(x,t)$. I am interested in talking about the position vector from $A, B$, and ...
1
vote
1answer
60 views

Is the “center-of-mass energy” in particle physics related to the center-of-mass frame or not?

For collision of particles the invariant quantity "center-of-mass energy" is defined, as done here. Since it is an invariant quantity it does not depend on the frame of reference chosen. So the name "...
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votes
2answers
77 views

Lorentz Boost of the Lab Momentums

Lets assume we have a two body scattering like; $$a + b = c+d$$ In the lab frame particle $a$ is moving with a certain beam energy $E_a$, and hits stationary particle $b$. Before the collision, ...
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votes
1answer
116 views

Doubt on relativity

I have a doubt: if in Classical physics the maximum speed is limited to the speed of light, will simultaneity be relative even in Classical Physics? Also, two observers in separate inertial frames, ...
2
votes
5answers
140 views

If centrifugal force isn't real then why am I being pushed on a merry go rournd? [duplicate]

I just finished my class on circular acceleration and I learnt that centrifugal force (outward force) is a psuedo force. It doesn't really exist. Now suppose I am going round in my car or a merry go ...
0
votes
0answers
34 views

Speed of light relative to itself? [duplicate]

At what point does stuff acquire this magical quality of its speed appearing invariant to all observers? I'd think it's a gradual thing, somehow tied to the Lorenz factor, but then again there's a ...
0
votes
0answers
37 views

Special relativity and photon [duplicate]

The photon is timeless particle from its reference frame moment it is emitted and absorbed is instantaneous then how would the photon which is never absorbed exist
1
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0answers
49 views

Spinor Lorentz Transformation

Why should the transformation between the solutions of the Dirac equation for different inertial observers be linear?
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votes
2answers
68 views

Modern Physics: Invariance of mass in an isolated system

Problem: Suppose two photons, one with energy 5 MeV and the second with energy 2 MeV, approach each other along the $x$ axis. What is the rest energy of this system? The thought track I used: 1) ...
1
vote
1answer
63 views

Why is linear momentum not conserved for a particle in a central force? [duplicate]

I am studying a two-body central force system in which the two particles, one of mass $m$ and one of mass $M$, experience a force directed along the line connecting the two particles. We can reduce ...
0
votes
2answers
103 views

What will the observer observe?

Consider the case where observer $A$ is at rest, and observer $ B$ is moving with speed $\frac{c}{2}$ (where $c$ is the speed of light) propagating a wave with wave speed $c$. So my question is what ...
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votes
1answer
64 views

If instead of $c$ we reformulate the Lorentz transformations to have $c \rightarrow c+1$, would any law of physics be broken? [closed]

What I mean is that suppose we can go to a speed greater than the speed of light, i. e., $c+1$, with the speed of light still being $c$. That said, in my new transformations, two events couldn't ...
1
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1answer
37 views

Equivalence principle and bending of a light ray

In some explanations of a phenomena of curved spacetime we have an example of a light ray emitted in a freely falling space ship perpendicular to the direction of a free fall. In this case, for an ...
1
vote
2answers
81 views

Applying Lorentz Transformation

Lorentz Velocity Transformation: $$v_x = \frac{v_x' + u}{1+\frac{uv_x'}{c^2}}\tag1$$ $$v_x' = \frac{v_x - u}{1-\frac{uv_x}{c^2}}\tag2$$ The speed of spaceship and scoutship are given relative to ...
0
votes
1answer
221 views

Are magnetic fields just modified relativistic electric fields?

Feynman's Lectures, Volume 2, says that the electromagnetic force is invariant in any reference frame, and the magnetic force in one frame becomes the electric field in another. And Wikipedia says: ...
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votes
1answer
14 views

Analysis of collision of a non-pivoted rod with a ball at one end?

Suppose a a unpivoted rod in free space is struck by a ball at one end and we know the initial condition what will be the outcome of the collision?
1
vote
1answer
32 views

What does the spacetime diagram for accelerated/non inertial observers look like?

Suppose that we are in flat Minkowski spacetime. There are many inertial observers moving at constant speeds relative to eachother and a single non-inertial observer moving with constant acceleration. ...
0
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0answers
31 views

Co-local events and time-dilation [duplicate]

favorite enter image description here I had this problem to do, and it's pretty straightforward, in earth's frame, the signal would be sent after a 100 minutes. My question is that, if we given the ...
-1
votes
2answers
90 views

Can someone explain Einstein's light clock?

The explanations for time dilation that I have seen all use the thought experiment of a photon bouncing between two parallel mirrors, which are themselves moving in a direction perpendicular to the ...
-4
votes
2answers
60 views

If The Flash ran a 100m race at 99.9% the speed of light, in what time would he finish the race according to himself and a stationary observer? [closed]

According to the time = distance/velocity formula it would take him 0.33 microseconds to complete. t = 100/(0.999 * 299 792 458) = 100/299 492 665.54 = 0.000000334 seconds (0.33 microseconds) My ...
0
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1answer
32 views

What is the accurate description of the following rotating system?

A man, standing on a rotating disc with angular frequency w starting from the center, moves radially outwards with a velocity of 6 meters per second. If an inertial frame of reference is placed at the ...
2
votes
0answers
36 views

To what extent is rotation relative (in GR and other theories)?

In Newtonian physics, rotary motion is absolute even though linear motion is not. More recently, there has been a hope that rotation can also be shown to be relative. Two definitions of relative A ...
2
votes
2answers
59 views

Acceleration in a rotating frame

From "Centrifugal force", Wikipedia: Acceleration [...] By applying the transformation above from the stationary to the rotating frame three times the absolute acceleration of the ...
3
votes
3answers
135 views

Doubt of speed of light

I have a question about how an observer sees the speed of light or the distances when at rest. Suppose two events occur simultaneously in $A$ and $B$. If someone in $X$ is watching, they will see ...
4
votes
0answers
96 views

Goldstein Classical Mechanics exercise 5.17 (3ed) conceptual

I am having difficulty understanding a concept in the "Heavy symmetric top" type of problems. I will include all of my efforts as to hopefully have someone easily point out what it is that I'm missing....
1
vote
3answers
105 views

What makes the Earth accelerate in a free-falling object's frame of reference?

If I'm an object in free fall near earth, then I'm an inertial frame of reference and I see the earth accelerating towards me with no force acting upon it. What causes that acceleration? The spacetime ...
9
votes
5answers
1k views

Inertia on a rotating disc?

If I toss a ball upwards in a train moving with uniform velocity, the ball will land right back in my hand. This is because the ball has inertia and it continues to move forward at the speed of train ...
0
votes
1answer
102 views

How fast would i have to travel for time to appear frozen?

i have to make a school project about something that interests me. so i thought about this question. if anyone could answer me, that would be nice :) (sorry if my English is bad) also im wondering ...