Questions tagged [relative-motion]

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How to derive relative velocity in two particle scattering?

While calculating the scattering cross section for one particle scattering we use the formula $$J_i=\rho v$$ where $\rho$ is the density of the incoming beam and $v$ is the velocity of the incoming ...
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78 views

Would impact angle matter on relativistic impactor?

I'm trying to calculate (for fun) a comparison between a kinetic impactor and an H-bomb. I would assume this to be a fairly straight forward problem involving kinetic energy and a table of various H-...
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2answers
79 views

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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31 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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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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36 views

Correlation between velocity and homogeneity of spacetime and isotropy of space

Considering only inertial frames of reference and constant velocities, does the fact that any velocity, with the exception for the speed of light in a vacuum, can be transformed, via an accurate ...
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1answer
44 views

Zero longitudinal momentum in Special Relativity

A particle is moving with an arbitrary momentum $p$ in K-reference frame. According to Jackson, "there is a unique Lorentz transformation in the $z$-direction to a frame K' where the particle has no $...
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85 views

Scalar versus invariant in Newtonian mechanics

I looking up coriolis transport theorem for rotating refrence frames and while reading through this derivation he wrote: In Newtonian mechanics, scalar quantities must be invariant for any given ...
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1answer
62 views

Can the Doppler effect account for the increase in an object's energy with velocity?

I am aware that the relativistic mass can be expressed in terms of rest mass and momentum, which seems to be the canonical explanation, but I am looking at an alternative way of visualising the ...
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40 views

Relative Motion Question - Inparticular method

Here is my question: Aircraft A is travelling West and aircraft B is flying in a circular, anti-clockwise holding pattern of 2km radius at 400 km/h. When ‘B’ is pointing South, the pilot ...
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66 views

Is there some kind of aether for rotations only?

Currently I'm reading "A briefer history of time". I understand how the Michelson–Morley experiment refutes the theory of an aether (like in "absolute frame of reference") for translation in space and ...
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59 views

Force impact when lifting objects traveling at a relative velocity of 0

During a break my colleagues and I came up with the following Gedankenexperiment I would appreciate if you guys helped us find the solution for: Truck (weight 5t) traveling at 80 kph with a tow-truck ...
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1answer
164 views

How can we find velocity, acceleration etc, of a revolving particle with respect to an observer inside the circle(not at center)

A particle is revolving in horizontal a circle of radius $R$ with constant speed of $|\vec{v}|$ and constant angular velocity $\omega$. There is another observer standing inside the circle, at a ...
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121 views

Wind resistance on moving body

Suppose that a vehicle is traveling 60 km/h north, and the wind speed is also 60 km/h going the same direction, would there be wind resistance, and to what extent? Also, if I put my hand outside the ...
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1answer
86 views

Speed with wind resistance

This is probably a basic question, but it has been a while since I did anything like this. If a boat is sailing forward at speed $x$ and the direction of the wind, with magnitude $y$, is either equal, ...
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1k views

What direction a flag on an object moving in the wind shows?

"The flag of a ship that is moving northward with 10 km/h, points exactly southwestward. The windsock at the lighthouse points under 30 relative to the western direction southward. Calculate the ...
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1answer
49 views

Relative Movements Agreement on Object speed

I am confused about Relative Motion.Lets suppose we have one train and two observer.One of them inside the train and the other one is outside.Lets think the outside observer see the train moves a ...
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1answer
36 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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18 views

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
57 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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29 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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14 views

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
67 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 ...
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48 views

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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97 views

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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40 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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1answer
44 views

How would one compute the path of an particle's motion from forces defined in different frames of reference?

I'm trying to write a computer program to render and play-back the path of a particle existing in 2D space given all forces acting on said particle. This is relatively easy to do if all forces are ...
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350 views

Question based on relative motion in two dimension

I came across this problem in my work book. A hunter is riding on an elephant of height $4$ $ m$ moving in straight line with uniform speed of $2$ $ m/s$. A deer running with a speed $V$ at a ...
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166 views

Relativity of simultaneity - under what conditions would two events happen simultaneously for frames $S$ and $S'$ when $S'$ is moving relative to $S$?

I feel like I have a fundamental confusion with the following exercise: I'm confident with my answer in (a), which is that $B$ must be within the light cone of $A$, or that $B$ is causally connected ...
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2answers
240 views

Directions of static & kinetic friction?

Static friction : Static friction opposes relative motion between two surfaces. The car is moving at some tangential velocity relative to the road. Thus, static friction should act in the opposite ...
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1answer
60 views

Accelerating towards a photon

What will be the relative speed and motion between me and a photon if I would have accelerated towards a photon that is moving away from me? Would it get away from at a slower velocity relative to me, ...
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1answer
119 views

Relative velocities problem ; how to draw useful diagrams if more than 2 things are changing?

Two students are canoeing on a river. While heading upstream, they accidentally drop an empty bottle overboard. They then continue paddling for 1.9 h , reaching a point 1.2 km farther upstream. At ...
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2answers
106 views

Changing mass and relative motion

Sand is pouring vertically on a cart at J [kg/sec], from negligable hight. The cart is standing on top of a frictionless surface. What force F do we have to apply to the cart for it to move at a ...
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2answers
81 views

The mechanics of retention of velocity/acceleration when an object is dropped from a moving body

This might seem a stupid question but please help me out because I'm very confused. We say that when an object is dropped from a moving body (moving with constant acceleration $a$) It has the ...
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2answers
574 views

The Meaning of Newton's Second Law of Motion Being Invariant Under Certain Transformations

What do we mean when we say that Newton's Second Law of Motion is invariant under Galilean transformations? Does it mean that the value of a force measured in one reference frame is the same when ...
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1answer
192 views

Classical Relativity: Clarification

I am working on a problem that states: "A swimmer capable of swimming at a speed $c$ in still water is swimming in a stream in which the current is $u$ (which we assume to be less than $c$). ...
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1answer
71 views

Waves and relative motion

Consider a situation in which a charged object which is colorless in a stationary (w.r.t observer) frame is accelerating in a circular path such that it radiates EM waves of specific frequency (...
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496 views

Simple Rotating frame of reference

I have a car moving in straight line with certain time-varying acceleration and there is another car moving in a curvilinear way along some curved path with some time-varying acceleration. The ...
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100 views

Is it possible to derive the Doppler effect formulas for sound using relative velocity?

Is it possible to derive the Doppler effect formulas for sound using relative velocity? If possible can anyone please explain it to me.
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49 views

Relative effects of forces

Excuse me for my ignorance but I really couldn't find a solution. According to Einstein, every happening is possible to describe by both of interacted objects. Is there any other way to describe the ...
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677 views

Is it possible to solve a 2D relative motion question using components of relative velocity?

This is a question based on concepts of two dimensional motion . Here's how the question is: A plank A is floating in air, gravity has no effect on it (See its coordinates in the figure attached). ...
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1answer
77 views

relative velocities

If two objects are moving relative to the horizontal and you have the real angle between the horizontal and the direction of travel of one object, how does this real angle differ from the angle ...
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1answer
80 views

Do blue and red shift oppose relativity?

The speed of light is constant does not depend upon the relative velocity of observer. But why there is blue and red shift ? Is it only for the reason that for this case the source of light is moving ?...
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2answers
57 views

Velocity as viewed from space

I got a problem which asks if the speed of a car in Oslo is 50km/hr what will be its speed when viewed from space. I have the relation between the velocities as observed from inertial and non-...
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1answer
68 views

Simultaneous observations in relativity

Consider an object which responds to two different signals A and B: it responds to signal A with blue color and signal B with red color. Also, it responds only to the signal that reached first. In ...