# Questions tagged [relative-motion]

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### Observer Watching a Ball Thrown Up on A Train [closed]

Let's suppose I'm on a train, moving with constant speed V1. At a time T1 I throw a ball up in the air, the ball do not accelerate but has constant velocity V2, and, in this hypotetical scenario, no ...
1answer
229 views

### Shouldn't the escape velocity of earth (with respect to earth) be less than $\sqrt{\frac{2GM}{R}}=11.2\,\mathrm{km/s}$

We know that the escape velocity of earth is, $$\sqrt{\frac{2GM}{R}}=11.2\,\mathrm{km/s}$$ Where $G=6.67×10^-11$ $M=\text{mass of earth}$ $R=\text{radius of earth}$ So if throw a object ...
1answer
1k views

### Acceleration along with Relative motion

I came across following problem: An Aeroplane is flying vertically upwards with a uniform speed of $500m/s$. When it is at a height of $1000m$ above the ground a shot is fired at it with a speed ...
1answer
244 views

### What is the Intuition behind Lorentz Transformation of time?

Suppose there are two spaceships, one at rest and the other one moves at a constant relativistic speed. The spaceship at rest is going to observe an event occuring at distance $x_r$ from itsel and ...
1answer
204 views

### If kinetic energy depends on your reference frame then which frames kinetic energy is dissapated during a collision to cause damage etc?

Say you have an object such as a car with mass 4,000kg moving at a speed of 20m/s relative to the ground in a straight line towards another object with, say, 2,000kg which is stationary on the ground ...
2answers
365 views

### Are my intuitions about special relativity right?

Suppose there is a bus which travels at constant speed $v=0.9c$, relative to my friend Eric who is standing still on the ground. I'm exactly in the middle of the bus, at distance $d$ form both ends, ...
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 ?...
1answer
61 views

### What relative motion tells me about a motorbike shooting out from a bus?

I imagined this situation: Suppose I'm on a motorbike inside a long bus that has a constant velocity v on a street. I start accelerating (in the direction opposite to the motion of the bus) till ...
1answer
490 views

### Rotating table with a groove having a ball within

A circular table of radius R is rotating with an angular speed Ω. It contains a groove of lenth L starting from the center of the the table and running along the radius vector of the table. A ball of ...
1answer
63 views

### Are these two systems equivalent?

1) a charge is placed next to a conducting wire with an electrical current being carried through it. 2) a moving charge is placed next to a conducting wire such that it is traveling at the same ...
1answer
63 views

### Rate that two objects are moving away from each other [closed]

Question : Two trains start from the same station at the same time. One goes due north at 30 miles per hour, and the other due north-east at 20 miles per hour. At what rate is the distance between ...
1answer
420 views

### Friction & relative motion

If there are two bodies that have zero relative velocity, does that mean friction will not exist between them, since friction opposes relative motion. In the figure below i have two wheels A&B, ...
1answer
75 views

### Motion of earth wrt. objects?

To "outrace the Sun" (or rather the earth) in Arctic latitudes, one can go much more slowly. Above Novaya Zemlya, on the 77th parallel, a plane doing about 450 km. p.h. would cover as much as a ...
0answers
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 ...
1answer
86 views

### How relativity works for static object and distances

Suppose there are two stations A and B. There is an observer standing on station B. A train starts from station A and moves towards B at a constant speed V. Relative to the train speed of the observer ...
2answers
92 views

### Relative speed with bike on train

If I am riding a bike on top of a train will the speed of the bike relative to the train and the speed of the train relative to the ground be added? For example: bike going 5mph train going 50mph. If ...
2answers
58 views

### Is there any video I can use to visualise why velocities change in moving rotating reference frames?

Suppose we have a car A moving along a straight path and another car B moving in a circular path. I know from the formula I have studied that the relative velocity of A as observed by B will not ...
3answers
417 views

### If two observer don't agree about distance traveled and the Times it takes, why they agree about relative speed?

Lorentz factor depend on speed, but to measure the speed, we need to know the distance traveled and the times it takes to get the ratio. But according to special relativity theory, for two equivalent ...
2answers
186 views

### Dark matter and relativistic mass change [duplicate]

Could the requirement of a dark matter for the missing mass in the universe simply be explained by objects having high relativistic mass change with respect to other objects? If this is not the case, ...
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 ...
2answers
249 views

### Does temperature depend on velocity of observer [duplicate]

The kinetic theory of gases states that temperature is a function of the average kinetic energy of a gas particle. But for the sake of our experiment lets say we have system of 5 molecules each of ...
3answers
136 views

### Kinetic energy coservation in different frames (non relativistic)

A mass $m$ is thrown horizontally on a ice rink with speed $v$. From the point of view of the thrower, the initial kinetic energy is $\frac12 mv^2$. Finally the mass stops a certain distance away ...
3answers
224 views

### Relativistic mass and velocity [duplicate]

I have read somewhere that when an object is approaching the speed of light then its relative mass is increasing by the formula $m=\frac{m_0}{\sqrt{1-(\frac{u}{c})^2}}$. Is this true? If yes then why ...
2answers
102 views

### What does “relatively uniform resonant frequency” mean?

In the book What If? from Randall Munroe, the author writes: Q: Assuming a relatively uniform resonant frequency in a passenger jet, how many cats, meowing at what resonant frequency of said jet, ...
1answer
93 views

### Centrifugal force in inertial systems

My textbook gives an example: There are two systems, $O$ is inertial and $O'$ non inertial. $O'$ is rotating whit $\omega=\mathrm{constant}$ and $O=O'$. We assume that a disc is rotating whit the ...
1answer
120 views

### How can a fly fly in a car? [duplicate]

From my understanding. if the car is moving at the velocity of 10 m/s and the fly is moving at the velocity of 5 m/s. the fly must move backward at the velocity of 5 m/s. but the fly seem to be able ...
0answers
84 views

### Laser on a Train Question [closed]

The two trains below are traveling at 1/2c. Each train has two identical pulsating lasers. One laser is pointed directly ahead of the train the other is pointed at 90 degrees to the direction of ...
1answer
447 views

### Relative Motion Calculations

Ok, so I was wondering if I could get a clear explanation of why we solve relative motion problems the way we do? so I'm given the problem where I have 2 cars, car A and Car B. Now car A is traveling ...
2answers
573 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 ...
2answers
55 views

### Can relative velocity be found?

Can you find the relative velocity between two cars with constant velocity of U1 and U2=-U1. In other words is there any kind of experiment you can do to understand that you are moving also and not ...
1answer
36 views

### Speed of sound in moving closed container

If I am standing in an airplane (air inside moving with the plane) with a someone talking to me while the plane is going 800k/hr. Would the the speed of the sound of the person talking to me go 800k/...
1answer
102 views

### The Ultimate Grand Race: Will the photon cross the alpha particle?

Question: There are $2$ points A and B, separated by a distance of $10$ light years. Suppose we have a light source at point A. An alpha particle is moving away from A at a speed of $0.99c$. As ...
1answer
426 views

### Relative velocity with relativistic speeds in 3D

I have a question regarding the relative velocities of two objects in $3$D space. If objects $A$ and $B$'s velocities are being observed by stationary observer $C$, what is the velocity vector $A$ ...
1answer
488 views

### Relative motion - Cylinders rolling between two identical planks

Today i ran onto this simple problem, which seemed to be interesting to me. Given the illustration bellow, the problem is states as: Two identical cylinders roll in between two identical planks. If ...
3answers
814 views

### Will two identical charges moving at the same velocity experience magnetic force due to each other? [duplicate]

I think they shouldn't since they are relatively at rest to each other. The actual answer to this question (it was in an exam I took) is that there will actually be a magnetic force acting on both of ...
1answer
130 views

### Apparent velocity of winds

If I run north at 10j m/s and the wind is also blowing north at 2j m/s , then do I feel a wind of 8m/s in my face if the relative velocity of of the wind to me is -8j m/s ?
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 $c$). ...
3answers
438 views

### Kinematics: relative velocity [closed]

The question goes like this: An aircraft, with velocity 580 km/h, is supposed to follow a straight path in the direction 38,0° in the northeast (measured from the east). The aircraft experiences a ...
1answer
70 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 (...
2answers
129 views

### What will happen if a helicopter flew still? [duplicate]

I discussed this question with some of my friends. I was given many solutions. Please provide me the exact solution for this problem. If a helicopter flew still in the same position for some hours, ...
1answer
65 views

### Around the world in one day [closed]

in the novel " Around the world in 80 days· they manage to get an extra day because they go from london to the East so my question is , what would happened if we could fly around the world at ...
1answer
347 views

### Symmetry between inertial reference frames

So my textbook says the following - roughly translated - in the context of Special Relativity: "Assume we have two observers, A and B, moving relative to each other. Observer A measures a velocity ...
1answer
147 views

### Are Electromagnetic Waves Independent from Their Source

Let's say we are on a latitude where the earth's rotation is 1,000 miles per hour. A rifle target is positioned a 1,000 yards away, perpendicular to the rotation. It's my understanding that a shooter ...
4answers
105 views

### Accelarating to speed of light in steps

I’m sure this will turn out to be a stupid questions, but… So Special relativity tells us one can no accelerate to speed of light because their relative mass will keep increasing toward infinity, so ...
2answers
182 views

### A question regarding inertial reference frame

We define a non-inertial reference as a reference frame which is accelerating. But the question is if it is the reference frame itself what is it accelerating with respect to? For simplification ...
1answer
558 views

### Does aeroplane moving against Earth's rotation cause relative wind (assuming otherwise a quiet weather outside)?

Although, I know some answers, I need more affirmative and accurate answers. Why is the journey time from London to Singapore less compared to Singapore to London? Is it because of Earth's rotation ...
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-...
6answers
200 views

### How can a particle which is not moving have an acceleration?

Suppose a rod is rotating around a fixed point located at an extreme point of it and there are two points on it. One, somewhere in the middle and the other at the other extreme.Call them $A$ and $B$ ...
1answer
842 views

### A relative motion question [closed]

A plane wishes to reach a destination that is 700km[S15°W] of its starting position. The plane can travel at 400km/h in still air. There is a 40km/h wind blowing from [W47°S]. What direction should ...
1answer
148 views

### How to form equations of motion of this kind?

I needed help with this question. I don't know how to form the equation of motion that describes the path of the boat in the following problem. A boat which is rowed with constant velocity $u$ ...