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Questions tagged [relative-motion]

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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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0answers
33 views

River boat problem when speed of river is equal to speed of boat relative to river [on hold]

the river moves in a circular path and the drift is hence (root 3 omega ) but how to find the time taken by the boat?
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2answers
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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
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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
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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
25 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
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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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1answer
135 views

A river is flowing with velocity 2√3 m/s

A river is flowing with the velocity of 2√3 m/s . A boat has to move from A to B . Find the minimum velocity of boat in still water. I think that the minimum velocity is achieved when the boat with ...
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3answers
59 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
64 views

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
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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
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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
62 views

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
77 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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0answers
29 views

Question about Relativity and Proper Reference Frames [duplicate]

If your in a space ship moving at relativistic speeds in reference to an observer on Earth, time would have to be going slower on the space ship and faster on Earth. However, wouldn't the Earth be ...
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2answers
121 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 ...
0
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1answer
59 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
29 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
50 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 ...
0
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1answer
66 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 ...
0
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1answer
55 views

Time in Lorentz transformations

I have a question about the meaning of time in Lorentz transformations. When we say that event A for S' occurs at t', I understand that this ct' is a distance, but I wonder exactly what does it ...
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0answers
24 views

Vertically move in a helicopter to go somewhere on Earth [duplicate]

Is it possible to go from point A to point B (which are on same latitude) by hovering above A and wait till the earth rotates to point B below and then come down vertically? I believe there would be ...
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3answers
36 views

Defining what it means for a reference frame to move with a velocity $\mathbf{u}$ with respect to another

In describing a Galilean transformation, for example, one might say that if a reference frame $S'$ is moving at a velocity $\mathbf{u}$ with respect to $S$, then an object traveling at a velocity $\...
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2answers
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Relativity: moving space shuttles [closed]

Two space shuttles $A$ and $B$ are moving in opposite directions. A person on Earth measures $v_A = 0,75 c$ and $v_B = -0,85 c$. What is the velocity of $B$ relative to $A$ (= $v_{BA}$)? So my first ...
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1answer
63 views

Time when two particles will meet [closed]

Particle P moves with constant speed of 13m/s always aiming at O . As P starts moving , O moves with constant velocity of 5m/s towards positive y-axis. Time taken by particle P to catch O will be? I ...
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0answers
24 views

Time interval to closest approach between two sattelites [closed]

Two artificial satellites are in circular earth orbits in the same plane. The orbit radius of one of the satellite is $r$ and that of the other is slightly greater than the other i.e $r + \Delta r$. ...
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0answers
25 views

Relative velocity and pseudo forces

If I am in a spaceship moving in deep space....... which is accelerating.... There is nothing around to compare my motion with.... How can I say even if I'm moving or not....if I say I experience a ...
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4answers
97 views

Why doesn't a ball thrown upwards fall behind us if we're moving forward?

If we consider ourselves traveling in a bus and if we a throw a ball upwards, the ball should fall behind us according to law of inertia, right? If so why doesn't the ball always fall behind us each ...
1
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1answer
37 views

Signs in relative vector addition

So I know the formula for relative vector addition is $$w = \frac{v-u}{1-\frac{uv}{c^2}}.$$ How do I chose when to use this formula or its inverse transformation for solving vector addition problems ...
1
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1answer
38 views

Charged particle and magnet, can this event vary relatively?

suppose we take a charged particle and a magnet and place them at some particular distance apart .Now let's take 2 frame of reference. [the charged particle and the magnet are in rest with respect ...
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1answer
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Deriving the equality between the external torque and the rate of change of angular momentum, for a system of particles

I've started working through Analytical Mechanics for Relativity and Quantum Mechanics by Oliver Johns and I'm stuck on deriving a formula. In the section titled "Change of Angular Momentum", Johns ...
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0answers
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Why does a charged particle experience lorentz force while moving in a uniform magnetic field?

Firstly, when a charged particle moves in an infinite uniform linear magnetic field, it experiences a force.But,how does the charge or how do we differentiate that the relative position of charge is ...
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2answers
44 views

Role of motion in experimental results

This page contains:"If you are in a closed room on a ship sailing at a constant speed and the ride is perfectly smooth...[t]here’s no physical experiment you could conduct to tell whether you’re ...
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0answers
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Does absolute motion/stillness exist?

I am not a physicist :) I (think I) understand the idea that motion can be relative in the sense that, I'm standing still inside a moving train in regards to the moving train itself, but I'm moving ...
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1answer
57 views

Relative velocity of a thrown object w.r.t. ground [closed]

An old-fashioned coke bottle is thrown straight out from the right side of a car at 10 m/s. The car is moving at 80 miles per hour. What is the speed of the bottle relative to the ground (in m/s)? I'...
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2answers
40 views

Motion at absolute 0 in relative to [duplicate]

Hypothetically, if we could get some type of particle to be at absolute 0 would it be technically still have relative motion due to an observer outside of earth. E.g earth is moving therefor particle ...
3
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1answer
44 views

Detecting external 'forces' in an inertial frame

Disclaimer: Science noob here, I may not use all terms correctly. I've read somewhere of the following situation: An observer is inside a room (elevator) with no ...
0
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1answer
64 views

Is it correct to use Newton's third law on all these scenarios? [closed]

So I was thinking about Newton's third law for sometime lately, and my problem is more about the concept, I'm fine with solving problems. I thought of these scenarios and tried to apply Newton's three ...
0
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1answer
35 views

Gravity on hovering objects

Imagine a remote controlled toy helicopter vertically takes off from a table and hovers at about one metre over the table that is of one metre height: hence, the total altitude is 2 metres. What will ...
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3answers
120 views

If there was but one object in the universe, can it be accelerating or not accelerating?

If there is only a single (material) object in the universe does it still make sense to speak of it as accelerating or not accelerating? I believe it might be an equivalent question to ask whether it ...
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3answers
2k views

Is electric current relative?

Motion as we know is relative. According to this current which is the flow of charges should be also relative . That means that if someone is moving with the same velocity with repsect to the velocity ...
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0answers
37 views

Cartesian basis vectors in polar coordinates

I'm trying to solve a problem which includes a spinning object and I want to find it's velocity vector with respect to an object moving in a straight line on the the x axis with constant velocity. I ...
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2answers
60 views

Is one side of earth faster at night and slower at daytime?

I'm reading Physics for Entertainment by Yakov Perelman and in it he says under "When we move around the sun faster" that at midnight the speed of the rotation of the earth is added to that of earth's ...
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0answers
53 views

Are there local coordinates for Schwarzchild spacetime?

In the Schwarzchild metric, $t$ is the time on the clock of an observer at infinity, and $r$ is the related to the area of a sphere by $A=4\pi r^2$. Are there more physical coordinates one could use, ...
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3answers
111 views

Speed vs Velocity of light in Light clock thought experiment

A related question has been asked multiple times (like here, here and here). But none of those answers are clearing my doubt. In fact they're furthering my confusion. My specific doubt is regarding ...
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2answers
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Aerodynamics of cycling into a tail wind

I was looking at Steve Gribble's Cycling Calculator , and I noticed that the aero resistance was higher going 40 mph with a 20 mph tail wind than going 20 mph with no tail wind. Why is this? I always ...
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1answer
64 views

Dark matter relative velocity

In Dark Matter Indirect Detection literature, it is usually said that the relative velocity of dark matter particles in the galactic halo is about $$ v \sim 10^{-3}c$$ See for an example this lecture ...
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2answers
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Can two electron moving in opposite direction move faster than light? [duplicate]

Suppose we are moving two electrons in opposite direction both having a speed of 1.6e8 meter per sec.When they will cross each other then their relative velocity will be 3.2e8 ms_1.Isn't it faster ...