All Questions
Tagged with relative-motion special-relativity
29
questions
16
votes
3
answers
10k
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How to derive addition of velocities without the Lorentz transformation?
Lorentz contraction and time dilatation can be deduced without Lorentz transformation. Can you deduce also the theorem of addition of velocities
$$w~=~\dfrac{u+v}{1+uv/c^2}$$
without Lorentz ...
- 1,714
118
votes
13
answers
42k
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If all motion is relative, how does light have a finite speed?
I've often heard that Einstein shattered the notion of absolute motion (i.e. all things move relative to one another) and that he established the speed of light as being absolute. That sounds ...
- 1,321
3
votes
1
answer
966
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Can we really not tell if we are moving?
It has been a while since I've thought about physics, however, I remember something about how if you are on a train with no windows that is going perfectly straight and is perfectly smooth, there is ...
- 133
12
votes
4
answers
6k
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Einstein's first postulate implies the second?
Einstein's two postulates of special relativity are as follows,
1. The principle of relativity: The laws of physics are the same in all inertial
systems. There is no way to detect absolute motion,...
- 5,371
16
votes
7
answers
11k
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Is acceleration relative?
A while back in my Dynamics & Relativity lectures my lecturer mentioned that an object need not be accelerating relative to anything - he said it makes sense for an object to just be accelerating. ...
- 1,657
4
votes
4
answers
505
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Chosing a reference frame in which the Earth is at rest and doesn't rotate
We may choose a non-rotating earth as our reference frame and ask ourselves: how about the planetary and stellar motions. A star at a distance of 10 million light years would turn around the earth in ...
- 6,841
7
votes
1
answer
2k
views
What is my acceleration in my own frame?
This is , I suppose not a good question , but I think I am missing something which confuses me in this question.
So my question is:
Velocity is relative. So suppose a car is moving at a speed $200 \;\...
- 2,797
6
votes
2
answers
1k
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Lorentz force law in Newtonian relativity
I know that in special relativity Electric and Magnetic fields mix together in different reference frames, but my question is about classical mechanics.
It seems weird to me is that the Lorentz Force ...
- 1,075
6
votes
6
answers
7k
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Inertial Frames of Reference - Inertial vs. Accelerated Frames
According to Robert Resnick's book "Introduction to Special Relativity", a line states the following as the definition of an inertial frame of reference: "We define an inertial system as a frame of ...
- 383
5
votes
2
answers
438
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Are my intuitions about special relativity right?
Suppose there is a bus which travels at constant speed $v=0.9c$, relative to my friend Eric who is standing still on the ground.
I'm exactly in the middle of the bus, at distance $d$ form both ends, ...
3
votes
1
answer
992
views
Relative Speed vs speed of light [duplicate]
Possible Duplicate:
Travelling faster than the speed of light
Someting almost faster than light traveling on something else almost faster than light
I've got two questions which are related and ...
- 203
-1
votes
3
answers
885
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If two observer don't agree about distance traveled and the Times it takes, why they agree about relative speed?
Lorentz factor depend on speed, but to measure the speed, we need to know the distance traveled and the times it takes to get the ratio. But according to special relativity theory, for two equivalent ...
- 111
-3
votes
3
answers
2k
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There must be free positive charges, moving oppositely to electrons for the wire with current to stay neutral
All popular expositions (e.g. these ones) of relativistic electromagnetism claim univocally that electrons in motion become more dense due to the speed. They teach that Lorentz contraction of charges ...
- 1,013
2
votes
6
answers
754
views
Detecting absolute motion inside a box
This is not a contradiction and I know it is impossible but still consider a thought experiment by me and point out if something is wrong. See the following picture and then the explanation follows.
...
- 2,479
1
vote
2
answers
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Objects travelling relatively to each other faster than light?
When we say that something is travelling a certain speed, it's really travelling that speed relative to the Earth. When saying the speed of anything, it is, for the most part, relative to something ...
- 123