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Questions tagged [relative-motion]

Use this tag for questions related to how objects move relative to other objects dependent on your frame of reference, and how this applies to special relativity.

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Question regarding friction acting on a disk on a conveyor belt [closed]

I have the following problem on which i am working A horizontal conveyor belt is running at a constant speed of $v_b = 3.0\hspace{1mm}m/s$. A small disc enter the belt moving horizontally with a ...
Hhh Hhh's user avatar
1 vote
1 answer
57 views

Confusion about sign conventions used in the Doppler formula

Wikipedia gives the Doppler formula as: $ f = \left( \frac{c \pm v_r}{c \pm v_s} \right) f_0 $ c is the propagation speed of waves in the medium. $v_r$ is the speed of the receiver relative to the ...
KDP's user avatar
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1 vote
4 answers
62 views

In an ideal situation, why should no friction exist when an object rolls? [duplicate]

As per my textbook, “a body like a ring or sphere rolling without slipping over a horizontal plane will suffer no friction in principle. At every instant, there is just one point of contact between ...
Saanvi Kalra's user avatar
0 votes
1 answer
33 views

How to calculate the relative speed when three bodies are involved? [closed]

Two trains A and B start from a station and move in parallel tracks with velocities 40 kmph and 60 kmph respectively. A man sitting in train A. watches a lady who walks inside the train B at a speed ...
Sandhra Baiju's user avatar
-4 votes
2 answers
64 views

What effect would relativity have for an objective with absolutely no momentum? [closed]

I know as you near the speed of light time slows down and mass increases to near infinite. What I'm curious about is what would happen if an object lost all momentum. No movement at all not even the ...
joshua landry's user avatar
1 vote
2 answers
43 views

Straight wire in moving uniform magnetic field induced emf

My question is a follow-up to this one. The green dotted line is the arbitrary loop which is constructed in the calculation of emf in the wire of length L. x is a variable which can be changed to ...
HazCam's user avatar
  • 11
0 votes
3 answers
81 views

Pseudo Orbital motion only due to Coriolis force

Planet, say of mass M and radius R is rotating with some angular velocity ω and a object of mass m (initially on the surface and rotating with the planet) was launched with velocity v vertically ...
Kyathallous's user avatar
1 vote
0 answers
70 views

Does relative velocity apply before or after the impulse?

I'm solving the following question from Kleppner and Kolenkow: My solution differs from the textbook solution not only in the magnitudes in parts (a) and (b) but also the conclusion in part (c). ...
Vulgar Mechanick's user avatar
2 votes
3 answers
64 views

If an observer was trapped in a closed box with no way to interact with the external surroundings how will he know if he is moving or at rest [duplicate]

I am a high-school student. Recently we learned the concepts of relative motion and velocity. The idea that anything in motion can subsequently be at rest depending on the frame of reference ...
AMAL's user avatar
  • 21
-1 votes
2 answers
116 views

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-...
Dron Bhattacharya's user avatar
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0 answers
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With what vel. would you have to launch an object vertically up from the earth's surface for it to land back again at it's initial launching point?

[Can skip reading this part] First of all, Newtonian gravity shall be considered whilst trying to solve this question. It's been on my mind for a long, long time and has been bothering me since. I ...
Kyathallous's user avatar
1 vote
0 answers
43 views

The stupidest question ever on relative kinematics and angular velocity [duplicate]

I am scratching my head on a very basic formula whose meaning escapes my intuition. On basically all texts of mechanics the following result is derived: Suppose that a rigid body is moving with ...
ebenezer's user avatar
  • 130
1 vote
2 answers
59 views

Euler Rotation Equations and invariance of vectors in different reference frames

Consider two frames, one which is inertial and the other one rotating w.r.t. to the inertial frame. Say there is a rigid body having angular momentum which is same/invariant in both frames. How is it ...
JAY YADAV's user avatar
1 vote
1 answer
75 views

How does relative motion work for an extended object?

I have this conceptual doubt which might be flawed very badly but I don't understand this particular thing. For example, if one end of a stick is moving with velocity $v_1$ and the other with $v_2$, ...
Krave37's user avatar
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2 answers
90 views

Does relative motion allow for speeds $>c$?

If motion is relative, (so if X was stationary and Y was moving at v m/s, we could think of this as Y being stationary and X moving at -v m/s), could we not create a scenario in which a stationary ...
bbqribs2000's user avatar
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1 answer
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The locus of the velocity vectors of a boat navigating in the sea under the presence of a very strong wind?

I already asked a question very similar to this one here and I think the solution would not work when the boat navigates in the sea when a very strong wind blows. That is I am trying to find the ...
Majid's user avatar
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-2 votes
1 answer
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Photon shot in opposite direction of spaceship, what is its relative velocity? [duplicate]

Okay, lets say you have frame S which is a spaceship who is travelling with speed v = c/3 relative to S' which is some planet Y. In the spaceship two photons are shot in opposite direction, to the ...
Day Time Gamer's user avatar
0 votes
1 answer
78 views

Calculating relative velocity: What am I doing wrong? [closed]

There are two objects A and B. Points P1, P2, P3 are in the same line, and P2 is exactly at the middle of P1 and P3 Suppose B is moving at constant velocity along the line P1 to P3. Thus, time taken ...
Atul's user avatar
  • 141
0 votes
1 answer
53 views

Determining the time elapsed between two events in

I want to determine the time a photon needs in order to cover a distance, say $l_0$, where $l_0$ is the length of a spaceship (reference system S'). So, the photon is going from one end of the ...
schris38's user avatar
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-2 votes
1 answer
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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 $1000 m/s$. ...
Jeffy James's user avatar
1 vote
0 answers
72 views

Coordinate transformation and absolute motion in general relativity

In special relativity, all motion is relative. But in the presence of black hole, all motion is with respect to black hole. The curvature of spacetime depends on how far we are away from the black ...
Chandra Prakash's user avatar
0 votes
1 answer
53 views

Special-Relativity and how things not accelerating appear to be the same in all frames of reference [duplicate]

As someone who knows very little special-relativity (and none of the math) I understood that if you take a car moving down the road (at constant velocity) and approaching an observer, there is no ...
244529's user avatar
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0 votes
3 answers
84 views

Conceptual meaning of frame of reference for kinetic energy

what does the statement The speed, and thus the kinetic energy of a single object is frame-dependent (relative) even mean? does the impact of a collision of moving bodies and henceforth transfer of ...
Ayanokouji Wannabe's user avatar
1 vote
0 answers
74 views

Attempting to solve the twin paradox without acceleration

My teacher told me that the key to solve the twin paradox is acceleration of the one that travel away. However, I feel a little bit uncertain that time change significantly by just a slightly nudge of ...
Thành Nguyễn's user avatar
1 vote
1 answer
77 views

Wording of Relative Velocity problems [closed]

I've been doing some relative velocity problems. The three main types I do are to do with cars, boats/rivers and planes/crosswind. I'm fine with cars as the wording is pretty straightforward - it is ...
Jay Chen's user avatar
0 votes
1 answer
53 views

To find the displacement of a rolling body

When calculating the displacement of a rolling body do we just calculate the displacement due to Vcom in a particular time t or additionally need to consider also the displacement that may be produced ...
Venkatesh Tiwari's user avatar
0 votes
2 answers
74 views

Accelerating body in a non-inertial frame of reference

If a body is subjected to a force, can I find a non-inertial frame of reference in which the body is not accelerating?
Nandu's user avatar
  • 21
0 votes
1 answer
102 views

How does one interpret the relative motion of an object in orbit as it compares to to the object it is orbiting?

How does one interpret the relative motion of an object in orbit as it compares to to the object it is orbiting? In flat spacetime, it's pretty easy to determine relative motion. If Alice sees Bob as ...
Spencer 's user avatar
0 votes
3 answers
69 views

Time Dilation and Spinning Reference Frames

If a spaceship approaches a rapidly spinning planet, would the planet's inhabitants , the inhabitants of the planet where the spaceship came from , and the spaceship's occupants observe time dilation ...
A Curious Mind 's user avatar
-1 votes
1 answer
48 views

Is it possible to detect your speed relative to light? [duplicate]

Let’s take two cases: (1) your velocity is constant and (2) you are accelerating. (1) isn’t the answer no, like that’s a core idea of Einstein’s relativity stuff? (2) I don’t know.
CTMacUser's user avatar
  • 201
1 vote
3 answers
135 views

Rotating Reference Frames And Their Phenomenon

In a rotating reference frame, while observing the proper motion of stars due to your spin, would you perceive time dilation when closely observing those stars?
A Curious Mind 's user avatar
0 votes
0 answers
51 views

Why is throwing a bullet by hands not effective as using a gun? [duplicate]

The bullet when fired applies equal and opposite force to the Gun, (Newton's 3rd law) Thus to keep the gun stable we apply some force which should be equal to the force applied by the bullet. If we ...
Krishn Sharma's user avatar
1 vote
1 answer
75 views

Principle of Relativity and the invariance of Newton's law in IRFs

Newton's law are form invariant under the coordinate substitutions: $$ \tilde{x^{i}}=x^{i}+a^{i} $$ This means that Newtons' equation of motion, $$ F^{i}=m \frac{d^{2} x^{i}}{d t^{2}} $$ (where $i=1,2,...
HRTninja's user avatar
0 votes
3 answers
117 views

Details on analyzing relative motion

I have been viewing some videos and reading some articles about Relativity and relative motion. My search abilities seem to be rather lacking. I am looking for articles, questions, and/or forums ...
Bryan Kelly's user avatar
-1 votes
3 answers
127 views

Any experiment for relative simultaneity?

Any introduction of relative simultaneity usually is like this : Alice on a train car shines two beams of light towards both ends where two clock are. She sees both clocks see the light at the same ...
Aug's user avatar
  • 291
2 votes
1 answer
47 views

Why is relative velocity taken with respect to final velocity of affected object?

I am practicing a conservation of momentum question: Two identical buggies move one after the other due to inertia (without friction) with the same velocity $v_0$. A man of mass m rides the rear ...
zxayn's user avatar
  • 73
0 votes
3 answers
127 views

Relativity of bodies in motion in space

I have learnt that if we are travelling in space we have no way to tell if we are moving towards something or if it is the something that is moving towards us; to either object they judge that they ...
Bedengus's user avatar
-1 votes
2 answers
80 views

Question on Special Relativity regarding light [duplicate]

Mine is a very basic question yet I haven't got a satisfactory answer so I turn to you. Special Relativity is based on two assumptions, one of which is that the speed of light is constant for all ...
Rudransh Joshi's user avatar
6 votes
1 answer
1k views

How is the expansion of space distinguishable from objects moving away?

Suppose you are standing 5 feet (1.5 m) away from me. Then I move 10 feet (3.0 m) further away. Now you are at 15 feet (4.5 m) distance from me. You say I moved. I say no; the space between us has ...
user avatar
0 votes
0 answers
72 views

What is the ceiling on the perceived relative speeds of two bodies, from the point of view of a third observer? [duplicate]

What is the ceiling on the perceived relative speeds of two bodies, from the point of view of a third observer's reference frame? We all know the ceiling on perceived speed relative to oneself is $c$. ...
it's a hire car baby's user avatar
2 votes
2 answers
430 views

Is all change movement? [closed]

Is there a change in the universe that cannot be reduced to movement? One counter-example should be enough. :) Heat is a type of change that was once thought to be qualitative, but is now realized to ...
Olle Härstedt's user avatar
0 votes
1 answer
121 views

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 ...
Samyak Sambuddha's user avatar
-1 votes
3 answers
174 views

Trajectory of light send from a moving box [closed]

In a closed box in inertial motion a ball bounces up and down vertically. Apart from this movement, the ball is motionless relative to the box. The trajectory of the ball seen by a stationary observer ...
externo's user avatar
  • 97
1 vote
1 answer
247 views

Is there a Doppler effect measured on the sunlight depending of the seasonal position of the Earth regarding the motion of the Sun through space?

The whole question is mentioned in the title but here I would add the conjecture that I am affraid that the answer(s) should be similar to a possible question about Michelson and Morley experiment...
Krešimir Bradvica's user avatar
0 votes
2 answers
76 views

In galilean relativity, is an observer assumed to be at rest only to simplify calculations, or is there a physical reason for this assumption?

I am a beginner in Physics and my teacher taught us "Relative Motion" yesterday. He said that the "Observer is assumed at rest." Is the observer assumed to be at rest only to ...
Anmol verma's user avatar
5 votes
2 answers
850 views

Does kinetic energy rely on the observer mass too since velocity is relative?

There is no 'correct' inertial reference frame according to relativity. Objects are only 'in motion' relative to an arbitrary inertial reference frame. So let us take the following example. A person ...
CPlus's user avatar
  • 1,009
0 votes
5 answers
1k views

Do released objects take the direction and speed of their parent frame's velocity, or just the parent frame's speed component?

Context: I'm working on a space game. I noticed that an unpowered object fired from a strafing spaceship appeared, as the released object moved, to curve in the direction the ship was strafing. This ...
The Architect's user avatar
-1 votes
3 answers
108 views

Location of an object in empty space [closed]

Is it correct to assume that if there is only one object in the void (really empty void), then its location (the answer to the question “where” this object is) cannot be established? You need at least ...
ggk hj's user avatar
  • 19
1 vote
1 answer
60 views

Simple classical mechanics problem to compute minimum distance attained between two ships moving with constant velocity

I have been reading the book "A Course in Classical Physics 1 - Mechanics" by Alessandro Bettini. I have reached a problem in the first chapter that I am having trouble with. The problem ...
scipio's user avatar
  • 121
0 votes
2 answers
68 views

Can a beam splitter be used to measure Earth's absolute motion through space?

Let say the Earth is not moving through space...Then a beam splitter that refracts the beam into 2 new created beams at an angle of 90° towards reflectors which will reflect the beams at 180° again ...
jbradvi9's user avatar
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