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Questions tagged [relative-motion]

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From the frame of reference of a colliding object, does the entire universe change direction when it bounces?

Consider three objects: a rubber ball, a spaceship, and an isolated brick wall floating serenely in the vacuum of space. From the perspective of an observer on the spaceship, the ball is moving ...
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10answers
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Is there any physical evidence for motion?

Let's say that we have 2 tennis balls in space, one being in motion (say, pushed by an astronaut), and the other one still. If we could take a snapshot of both tennis balls, would there be any ...
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1answer
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Is the kinetic theory of gas relative in nature

In kinetic theory of gas the foremost assumption is that the temperature of an object is due to the kinetic energy of the atoms/molecules contained in it. But as we know that kinetic energy is a ...
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1answer
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How does relative motion theory adjust other variables than kinematics' basics like velocity or displacement?

I have been confused on this concept for a while - suppose a boy is going from east towards west with some velocity on a bicycle and rain is falling in a vertical downwards direction. Then, if we ...
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3answers
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Motion of a boat in a stream

We are doing problems involving boats sailing from one shore to the other. Usually, in such problems we are told the velocity of the boat with respect to the water and the angle at which the boat sets ...
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0answers
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Relativistic trajectory in a constant electric field

I'm trying to write the trajectory ($y^i = y^i(t),\ i \in \{1, 2, 3\},\ y^0 = t$) of a particle seen from an inertial reference frame, ${\cal O\ '}$, that moves along $y^2$ axis with constant speed $(...
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3answers
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A textbook problem on vectors [closed]

I am stuck on a textbook problem on vectors (a new topic for me). The problem given in my book says: A man can swim with a speed of 4 km/h in still water. How long does he take to cross a river 1 ...
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2answers
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Question regarding relative velocities

Suppose I am solving a question, which has statement written the velocity of boat in still water 10m/s Now the question turns to a flowing river, so what will 10m/s be, the relative velocity of ...
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3answers
179 views

How to conceptualize Newton's apple?

I have no physics background, which is the genesis of my question. In pop-science, it is frequently mentioned that Newton's apple didn't fall toward his head, but rather that his head came up and ...
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1answer
64 views

Unreachable relavistic particle in accelarated motion

Let's say I have a particle in a uniformly acclerated motion such that $$ a_\mu a^\mu = -g^2, \quad g > 0\ {\rm and\ constant} \tag1 $$ I want to prove that any signal coming from a apace-time ...
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0answers
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What is topocentric horizon coordinate system?

I was going through the book Orbital Mechanics by Howard Curtis and in the book he talks about topocentric horizon frame and its angular velocity about an inertial frame? What does it mean and how do ...
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1answer
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What is definition of motion? [closed]

I know this question is too basic and silly. But if you really contemplate about the definition of motion which say that it is "change" in position over time then you will find a loop. "Change" is ...
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4answers
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Why can't we define absolute rest?

If, according to the theory of relativity, as objects gain velocity and approach the speed of light then time for them slows down, why can't we define absolute rest as the inertial frame in which time ...
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Curved space relative motion

Suppose I live in a 2d curved space. I can describe intrinsically the motion of a particle which moves in my 2d manifold using time "t" as a parameter. Now suppose there is a second observer (let's ...
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1answer
36 views

Relative velocity, momentum conservation

I am having difficulty in conserving momentum for objects moving with relative velocities. For example: A block of mass $m$ with a semicircular track of radius $r$ rests on a frictionless ...
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1answer
67 views

An Evil Vector Problem! [closed]

A person is walking on straight road starting with a velocity $v$, the direction of of air ,observed by him makes an angle $\alpha$ with his is direction of motion. Now during the race, he finds ...
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2answers
195 views

Why are there so many Doppler Effect formulas?

I was just introduced at my class, a phenomenon, known as the doppler effect, where the observed frequency increases as the source/observer approaches each other, but decreases, if they were moving ...
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1answer
65 views

Relative velocity from space-time diagram

Consider two frames of reference, with velocities V1 and V2 relative to an initial ground frame. I have made the space-time diagrams for the three frames (Time represented on Y-axis). As far as I ...
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4answers
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Motion between two particles in a relative manner

Suppose a particle A is travelling in east direction with velocity of x m/s and another particle B is travelling with velocity y m/s in the west direction. Why does the the particle B appears to move ...
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2answers
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When formulating and performing experiments for quantum theory do physicists account for us constantly moving through non-zero energy vacuum?

Problem: If we suppose that each smallest possible point in vacuum is a size of Planck length and that point is somehow affecting that particle with spontaneously emerging non-zero energy, then as our ...
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2answers
53 views

relative acceleration of ball in a train [closed]

A boy is standing in a train with a ball in his hand. The train is having a constant acceleration equal to x m/s^2. While still in train he throws the ball with a constant velocity of 20 m/s at an ...
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1answer
38 views

Relative motion between two particles

I already know the relation of relative velocity as : Vab=Va-Vb So is there any derivation for this relation or is just how it is defined? Relating to this i am finding some hard time to imagine why ...
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3answers
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Relative motion with relativity [closed]

In an inertial frame of reference (let's say a car moving with certain constant velocity in which I am sitting) If I observe the motion of another car through my frame of reference i.e.car, will I be ...
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1answer
68 views

Free fall time after being accelerated [closed]

An elevator car whose floor-to-ceiling distance is equal to $2.7m$ starts ascending with constant acceleration $1.2 m/s^2$; $2.0 s$ after the start a bolt begins falling from the ceiling of the car. ...
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1answer
87 views

Is there anything in physics that is absolute rather than relative? [closed]

Are there physical quantities that are absolute rather than relative? Things that do not depend on the reference frame? Perhaps I just haven’t learned about them yet. Original (before edit by @G....
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2answers
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How can we define event to be proper and improper when there is no absolute frame of reference [duplicate]

Suppose in an empty space two rocketships exists with person A and B of same age inside each. Let A move with velocity c/2 away from B and return. They'll find out that B grew older while A didn't ...
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2answers
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Why can't we take space as universal frame of reference?

Suppose we have a ball filled half with water in space with nothing else around (nothing else in the whole space except the ball) and suddenly it accelerates for time t. obviously, there would be ...
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2answers
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Relativity and electromagnetic field

I have a question regarding Misner, Charles W.; Thorne, Kip S.; Wheeler, John Archibald (1973), Gravitation ISBN 978-0-7167-0344-0. It is a book about Einstein's theory of gravitation. At the page 79,...
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1answer
53 views

Why ball fall at same location from where we throw it? [duplicate]

I have a silly question. As we all know earth is rotates at a speed of 460 m per sec. So if I throw a ball in the air for 10 sec than the ball must fall 4600 m away from me but these does not happen ...
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0answers
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Relative angle and velocity binning around one particle

Let's suppose particle positions and velocities are represented as $P_i = [p_x \; p_y \; p_z]$ and $V_i = [v_x \; v_y \; v_z]$. While, x,y,z represents the 3 components of position and velocity vector ...
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2answers
56 views

What are the necessary conditions for relative angular velocity to be defined? [closed]

I have certain doubts related to the definition of relative angular velocity .My textbook defines it in the manner given below:- $$\omega_{AB}=\frac{v_{AB}}{r_{AB}}$$ $\omega_{AB}$ is the relative ...
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1answer
50 views

Can we move without moving? [duplicate]

So here is the question, If I jump and hover over the ground for sometime why don't we move away from the point I jumped from? Because earth is rotating so if I hover long enough we should move from ...
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2answers
61 views

Meaning of the term speed of light in context of an object of non-zero mass

We know from GR that an object of non-zero mass cannot propagate at light. I have a problem with the term speed of light. Does it mean the relative speed of that object with another object or frame of ...
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11answers
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If absolute velocity does not exist, how can we say a rocket accelerates in empty space?

If a rocket in space fires its thrusters, it is propelled forwards as per the laws of motion. This can be measured by its position relative to other bodies in the universe. Hypothetically if there ...
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2answers
76 views

Would close to light speed travel be possible if all atoms in the system were instantly given “forward motion”?

I have heard people say that based on our current understanding and ideas for possible/current technology no person would ever be able to even travel at a solid (70-80%) the speed of light because ...
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3answers
145 views

Why cannot we determine our own velocity?

I know it would violate the principle of relativity. But have there been serious experimental attempts to contradict that principle? If I am in a moving train without windows and totally sound proof,...
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0answers
52 views

Question about relative motion by Galilean Transformation?

You are piloting a small airplane in which you want to reach a destination that is 750 km due north of your starting location. Once you are airborne, you find that (due to strong but steady wind) to ...
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1answer
38 views

Interpretation of directional depenedence in special relativity

I am reading AP French's book, Special Relativity, because I have always wanted to understand the subject, and I have just attempted to answer the following question (1-22) in the book: An electron ...
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3answers
67 views

Kinetic energy of an object

We know that motion is relative. So let an object(o) be moving with a certain velocity with respect to an object (A).If another object (B) is moving with respect to (A) at a given moment and they ...
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2answers
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Is the weight of a bicycle frame significant compared to the body weight?

Some of my colleagues had a discussion about the question if the weight of a bicycle frame is significant compared to the weight of the rider‘s body. One argues that the weight of the frame can simply ...
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1answer
870 views

Galileo's law of odd numbers

The Galileo’s law of odd numbers states that the distances traveled are proportional to the squares of the elapsed times. In other words, in equal successive periods of time, the distances traveled by ...
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3answers
151 views

Sign conventions for relative velocity problems

I am having trouble solving relative velocity problems because I can't seem to understand the sign that goes along with the velocity of different objects. $$ v_{ac} =v_{ab} + v_{bc}. $$ How do the ...
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4answers
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What is the correct formula for relative velocity?

I have consulted byjus.com, HC Verma and Khan academy, all are saying different. byjus and HC Verma book is saying that formula for relative velocity is $V_a +V_b$ but in Khan academy they are telling ...
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2answers
85 views

Throw a ball AT a moving train, in what direction does it reflect?

You are standing at a platform, with a ball. a train approaches and u throw the ball at it in a straight line from a small distance. in what direction des the ball reflect off? heres what i think, ...
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2answers
134 views

Does a helicopter that simply hovers remain in the same spot on earth? [duplicate]

Ignoring statistical variation in wind, will a helicopter that only applies force perpendicular to a perfectly sphere earth remain in the exact same spot relative to the earth? I am arguing with ...
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1answer
60 views

Speed of light as the maximum speed and movement course

Assuming we have 3 objects d,e,f moving on the same line while e is stationary, d is moving to the left at 'almost speed of light' and f is moving to the right at 'almost speed of light'. What is the ...
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0answers
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Issue deriving observed period of a moving signal in different reference frames

Consider a receiver on Earth measuring radio waves from an incoming slow moving UFO. Here is my attempt to find the period of the signal as measured by the earth observer. T' is the period of the ...
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1answer
41 views

Velocity of approach which changes continuously [closed]

There are two particles A and B which are moving with constant speed $v$ and $u$ such that $v$ is always directed towards B. At $t = 0$, the separation between A and B is $l$ and $u$ is perpendicular ...
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2answers
56 views

Throwing/Dropping an Object

When we throw or drop an object while moving, do we impart it our acceleration or velocity or both? Say i throw a ball at 5 m/s (relative to me) while at say, 30° to my direction of motion, then will ...
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1answer
68 views

Moving moon explanation

I saw the moon moving in a fast pace several times with the naked eye, even during day time when its cloudy. How is that possible? I asked my teacher about it and he said its just an illusion, but ...