All Questions
Tagged with kinematics inertial-frames
95 questions
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Regarding motion [closed]
I am conducting a thoughtful experiment
involving a train that accelerates at 10 m/s^2
. The train has a long passage of
12 m, and I am standing in that passage. If I jump up straight and remain in ...
user437229
0
votes
1
answer
100
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Regarding Motion
Suppose there is a train that travels from point A to point B, and some distance vertically from point A, there stands an observer, let's name them O1. Beside O1, there is another observer, O2, who is ...
user437229
0
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2
answers
31
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Do these two refer to the same reference frame? [duplicate]
What exactly is the difference between a reference frame and a coordinate system (with respect to classical mechanics only)?
Can we claim that these two coordinate systems is from same reference frame?...
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0
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4
answers
169
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Motion of person in bus in inertial and non-inertial frame
A person is sitting in a bus that is moving with constant velocity, due to friction their is no relative velocity between bus and the person.
Suddenly the bus starts to move with a constant ...
-1
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1
answer
126
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How Fast Must a Man Run to See Rain Falling horizontally?
The fact that tan 90° is undefined indicates a key issue in the problem.
Does this mean it is impossible to observe rain falling at 90 degree?
When rain is observed to be falling at 90° with the y-...
0
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2
answers
80
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Vectors in inertial and non-inertial frames
Trying to understand how vectors change in inertial and non-inertial frames
Am I right in saying vectors are defined by their invariance under coordinate transformations? My main question is are ...
- 75
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2
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84
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Solving a PDE using $x-vt$ as a variable
So I was reading this Landau and Lifshitz paper:
https://doi.org/10.1016/B978-0-08-036364-6.50008-9
The article can also be found without a paywall by just searching its title, "On the Theory of ...
-2
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1
answer
61
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The distance problem [closed]
Say a car has to move from Point A to Point B on the surface of the earth. The car starts from rest at Point A at time $t=0s$ reaches point B at time $t=10s$ with a constant velocity of $1000 m/s$. ...
- 85
3
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1
answer
93
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Conservation of mechanical energy and reference frame
Is it possible to apply the law of conservation of mechanical energy in all reference frames, including non-inertial frames, when there is no frictional or drag force? My personal belief is that it is ...
1
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2
answers
105
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Inertial and non-nertial observer
Let's assume there are two observers 'A' and 'B'. B is at ground and A is moving with an uniform acceleration ('a') with respect to B. Will A be an non inertial observer with respect to B? (As we know ...
1
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2
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648
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Shooting a bullet in motion
If a bullet is shot from a firearm from a moving car in the direction of movement, would the speed gained with respect to the car be same as the speed of a bullet that is shot from an immobile gun?
I’...
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1
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133
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Velocity of Separation and Relative Velocity
I have some problems in understanding a concept, which has been used in the problem in the picture:
I don't understand what are we actually using to solve this question. Are we using relative ...
1
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0
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94
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Feynman physics relativistic mass
Here is the page I read from Feynman physics. My question is when we ride along in a car moving with horizontal speed of the particle one then we get situation in fig 16-3a, according to last section ...
- 329
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1
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55
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Question on work done and frame of reference [closed]
While solving a question which is.....
If an object is kept in a non inertial frame moving up with acceleration 'A' find the work done by pseudo force on the object taking a person standing on ground ...
- 105
1
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2
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480
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How important is the concept of rapidity in relativity?
After studying the concept of rapidity and the associated formulation of special relativity in terms of hyperbolic trigonometric functions of rapidity, I've come to understand the elegance of this ...
- 523
4
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5
answers
746
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Can't understand a statement about motion
From the book where I am studying motion, It says
Motion is a combined property of the object under study and the observer. There is no meaning of rest or motion without the viewer.
I know that, for ...
- 157
3
votes
7
answers
941
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What exactly is rest?
Consider a position-time graph for a particle's motion, where the y-axis is position and the x-axis is time (in seconds).
Now, consider the question:
At what point in time is the particle at rest?
...
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5
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5
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How is a change in KE the same in every inertial reference frame?
This is not about special relativity, so assume speeds are much less than $c$.
This article says a change in kinetic energy (KE) remains constant in all inertial reference frames.
So the kinetic ...
- 410
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1
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48
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Kinetic energy consistency
Suppose a vehicle 1 is on the top of another vehicle 2 (we can think of it like a big platform).
Imagine the following independent experiments:
Suppose that the top vehicle accelerates to a speed $...
- 31
2
votes
2
answers
423
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Transformation of the Lorentz factor when a relativistic particle partially absorbs energy from a photon?
I came across this paper (on arXiv) that says when a particle with high Lorentz factor $\Gamma$ meets a radiation beam and absorbs some energy $\epsilon$, it's Lorentz factor transforms like so (Eq. (...
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1
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64
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Why does light change its path in different frames of reference?
A similar question has previously appeared on this site:
Light in Different Reference Frames
But my question is slightly different in nature. The difference would be clear after a read of this ...
- 161
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2
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905
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How Newton's first law works in space?
If we have object in space and apply force over it. Does will the object continue his motion forever.
When First law of Newton states:
An object at rest remains at rest, and an object in motion ...
0
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0
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258
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Initial speed of a released object from a moving object
For example, if a helicopter is moving upwards in constant velocity of 20 m/s and at some height an object is released from the helicopter, why does the object has an initial velocity of 20 m/s and ...
- 5
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3
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137
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Do relativity and frame of reference contradict each other? [closed]
Relativity states that nature doesn't depend on how we look at things, and a physical process is the same no matter what perspective we choose to think about it in, and frame of reference is a set of ...
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3
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282
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A question about relative motion and how to make sense of it
So, here is the question:
Assuming the 2D Cartesian system and the basis vectors $\hat{i}$ and $\hat{j}$, we have two cars A and B located at (0,6) and (-30,0) respectively. Car A starts moving with a ...
- 169
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65
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Definition of acceleration and inertial frames of reference
Sorry for my math lacks, I hope you'll be patient even if this question will probably not be clear.
How can we define acceleration in special relativity (and in Newtonian mechanics were we apply ...
- 97
4
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3
answers
1k
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Kinetic energy "paradox" -- where am I wrong here? [duplicate]
Body $A$ is at rest and has mass $2$, so the energy required in order to accelerate it to a speed of $v$ is $v^2$, and so the energy required in order to accelerate it to a speed of $2$ is $4$.
On the ...
- 143
1
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1
answer
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Special relativity - Center of mass frames vs Laboratory frames
In the reaction where particle A hits particle B, which is at rest. This produces
particles C and D. For the minimum energy of particle A for the reaction to take
place I have two calculations. I don'...
- 172
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3
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114
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Is there any explanation from special relativity regarding the speed of a fly inside a car?
I have faced a scenario mentioned in this Question.
There was a fly inside my car and I was travelling so fast. shutters are opened in the car. I observe that when I slow down and accelerate, there ...
- 179
0
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1
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129
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CoM-and-relative velocity
In our scrip we are considering the elastic collision between two particles, one with inital velocity $\vec v$ and the other $\vec w$. We also consider that the particles have the same mass.
...
- 1,626
1
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1
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140
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Velocity of an object with respect to the same object
I know that velocity of an object with respect to the same object is a null vector but I'm not able to get a grasp of it.
Whatever I had thought till now is that if I'm sitting in a train (which may ...
- 882
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1
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263
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What's the speed of the train with our point of reference being the person who's moving inside the train? [closed]
A person moving in a train with the speed of 1m/s to the right, while the train is moving in the same direction with the speed of 10m/s
From the person's point of view "considering that the ...
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2
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1
answer
210
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Is there a word to describe when things are moving individually, but have a net velocity of zero?
I know this is a strange question, but I know there must be a word for it.
So imagine a case where, taken as a whole, the net velocity of all particles equals zero, but each individual particle is ...
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2
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2
answers
144
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Can I apply Newton's equations of motion to relative motion?
We know that
Velocity of A relative to B is
$$ \vec v_{A|B} = \vec v_A - \vec v_B $$
and Acceleration of A relative to B is
$$ \vec a_{A|B} = \vec a_A - \vec a_B $$
So, is it correct to do this to ...
- 227
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2
answers
319
views
Why is relative motion at constant velocity the same as being at rest?
If I am a passenger who plays catching-the-ball game inside a vehicle that moves with a constant velocity in a straight road, why can I catch the ball repeatedly that as if the vehicle is at rest? How ...
user282164
1
vote
1
answer
62
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Interpretation of a basic Special Relativity problem using tensors
I'm solving a problem in which a muon with a half life of $\tau=10^{-6}s$, generated at 30km of altitude, travels at an unknown velocity. I'm asked to calculate its velocity and then the distance in ...
- 193
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1
answer
83
views
How to find the coordinates for a worldline with $y=z=0$ that experiences constant acceleration?
I'm studying some lecture notes on special relativity and at some point one considers an inertial system in which a particle has $4$-velocity and $4$-acceleration given by
$$U = (c\frac{dt}{ds}, \frac{...
- 123
0
votes
1
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51
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A question about the Lorentz transformation of "infinitesimals"
Notations conventions: $p$ stands for the momentum (so $d^3p$ is the differential element according to which we integrate, for the $3$ space coordinates). A Lorentz transformation is denoted by $\...
- 175
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2
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313
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Dependence of Lorentz factor on only a component of velocity
In cases of two- or three-dimensional space, why doesn't the Lorentz factor of a component of 3-space momentum depend on only the corresponding component of velocity? That is, why isn't there, for ...
3
votes
1
answer
2k
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Proof of Lorentz invariant phase space factor
I was going through the following proof of Lorentz invariant Phase space (in Modern Particle Physics by Mark Thomson).
Could someone please help me understand how the equation in the box is valid? If ...
- 129
2
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3
answers
253
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How do we define $G$s?
I am going to explain what I think I know and how that leads up to my question - please correct any false claims I make or conclusions I draw.
I initially thought that $G$s were defined purely by ...
- 318
1
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0
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60
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General 2D equations of motion in non-inertial relativistic frame of reference
Let's assume that there is inertial frame of reference $S$, and the observer is at the origin of this frame at time (associated with this inertial frame) $t = 0$. The observer has own frame of ...
- 11
1
vote
2
answers
2k
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What is the maximum deflection angle of a pendulum in a car, when the car, initially at rest, accelerates suddenly? [closed]
I was doing Kleppner-D.-Kolenkow-R.J. and I came across the following problem:-
A pendulum is tied vertically to a car at rest, the car suddenly accelerates at a rate A. Find the maximum angle of ...
- 127
0
votes
1
answer
467
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Partial derivative of a 4-velocity
Trying to do some basic manipulations with 4-vectors and I have a question about the proper (no pun intended) approach. It's probably easiest if we look at a simple example. So let's define a 4-...
- 292
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0
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53
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Energy and momentum conservation equations for frame moving at speed $v$
A particle of rest mass $M$, while at rest in the laboratory, decays into a particle of mass $m$ and speed $v$, and a photon of frequency $f$ moving in opposite direction.
I want to look at this ...
- 83
2
votes
3
answers
511
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Four-vector of a proton as seen from the rest frame of another [closed]
I have a question regarding the four-vector of two protons. My task is to determine the four-vector of one proton as seen from the rest frame of the other.
I'm having a hard time understanding ...
- 121
0
votes
1
answer
2k
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Lorentz transformation four momentum to to lab frame
I would like to know how to transform from a generic four momentum of the form:
$(E, p_x, p_y,p_z)$
to the frame where the $y$-component is zero:
$(E^\prime, p\sin\theta, 0, p\cos\theta)$
What is ...
- 357
0
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1
answer
193
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Derivation of simple Lorentz boost identity, $dp'_z/dp_z$
Given a Lorentz boost in the $z$-direction, in natural units we can write
$$p'_z = \gamma(p_z+\beta E)\,,\;\;\;\;\;E' = \gamma(E+\beta p_z)\,.$$
In Peskins & Schroeder's Introduction to QFT, p. ...
- 145
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0
answers
40
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Calculating center-of-mass enegies for processes/reactions
Let's take any arbitrary process: $d\overline{d}\rightarrow g$.
Let's say I am interested in the center-of-mass energy at which the process can take place. How can I calculate it for any given ...
user248824
1
vote
3
answers
3k
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How to prove the relativistic momentum? [duplicate]
As far as I know, the relativistic momentum of a particle is given by the equation: $$p=\frac{m_0v}{\sqrt{1-\frac{v^2}{c^2}}}$$
where $m_0$ is the mass of the particle and $v$ is the velocity of the ...
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