# All Questions

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53 views

### Is there anything as absolute and not relative or which has no concern with reference frame? [on hold]

Is there anything as absolute and not relative or which has no concern with reference frame? Or I don't know anything yet?
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 ...
49 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 ...
56 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 ...
9k views

### 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 ...
140 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,...
62 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 ...
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 ...
51 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 ...
56 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 ...
41 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 ...
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 ...
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 ...
122 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 ...
61 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 ...
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, ...
135 views

### Inertial and non-inertial frame

How to define an inertial frame of reference mathematically? I want a definition with proper chosen coordinate axis which will help me to differentiate it with the non inertial ones. I have been ...
47 views

### Differentiating linear and non-linear motion

If there is a Person sitting in a vehicle which is moving, how could he find out whether it's in motion and if he figures that out, how does he find out whether it's accelerated or non-accelerated?
76 views

### Super luminal speed paradox? [duplicate]

Chosing a reference frame in which the Earth is at rest and doesn't rotate is related, but different. Here I'm asking if there is a paradox and if my attempt at resolution has merit, and if not ...
90 views

### Why dont we account the rotation of the earth in aircrafts? Is it just because of the air or is there more to it? [duplicate]

Today there was a seminar regarding modern air crafts held in my school. At the starting of the lecture, we were asked a question which I found quite intriguing. "Why does a helicopter or a fixed ...
67 views

### Doubt on how I have applied Newton's law of motion

I have found several questions where the pseudo force is applied in the wrong direction, and I am confused whether I m correct or not. The question is something like this. Thin threads are tightly ...
90 views

### Can we really not tell if we are moving?

It has been a while since I've thought about physics, however, I remember something about how if you are on a train with no windows that is going perfectly straight and is perfectly smooth, there is ...
61 views

### Total energy of an object in motion in free space

In order to impart motion (additional motion) to an object in free space, inertia "soaks up" an given amount of energy prior to additional movement, which is related to its mass, irrespective of any ...
122 views

### Explain the relative motion between two particles of a rotating rigid body

A rigid body is defined as a collection of particles in which distance between each pair of particles remains constant. I was taught that the motion of any one particle of the rigid body with respect ...
84 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 ...
54 views

### Earth's movement around the Sun

My question is - because of sun's movement around the milky way, Earth never reaches at the same point where it started from. Then how can we say that it circles around the sun in 365 1/4th days.
1k views

### If you are sitting completely still inside of a moving car are you at rest?

My teacher and I had an argument in class where I stated that motion is undefined without a reference point and that you could just as easily claim that the road is moving backwards at the opposite ...
129 views

### How can I visualize the center of mass (center of momentum) frame?

I know that the CM frame is the frame in which the total momentum of the system adds up to zero. For example, if I imagine two bodies m1 and m2, with m1 = m2, one moving at the speed v1 = v and the ...
194 views

### Special Relativity - Why does time dilation cause length contraction? [duplicate]

As an object moves faster, its time runs slower by factor X. I get why this is the case, but I'm not sure why distance is decreased by factor X as well. Questions: 1) Why does a moving object's ...
668 views

### What makes an object to be at rest?

We understand both motion and rest are relative. But me and my friends always discussing about this kind of thought experiment involving a single object (for example, a particle with mass or massless ...
694 views

### Angle of reflection of an object colliding on a moving wall

Consider an object colliding elastically with an inclined wall (with much bigger mass than the object) as in picuture. The wall is at $45°$ and it is moving. $(A)$: frame of reference of the wall (...
157 views

### To what extent is acceleration relative?

I realize there are answers to my question many places across the internet and many places on this site, but from what I have seen, most of them either involve terms I don't know or assume you can use ...
952 views

### What happen when a helium balloon is floating inside a moving train?

Let's assume a helium balloon is suspended into the floor of a moving train. We already know how it will react during acceleration, deceleration, and constant speed as illustrated in figure no 1, 2, ...
390 views

### Inertial reference frames vs. non-inertial reference frames

I have a problem concerning the motion in different frames of reference. This example confused me: We've got a train which is moving and we declare the rail was our inertial frame of reference (with ...
252 views

### Centrifugal force intuitive explanation [duplicate]

I would like to know if centrifugal force is only apparent why all the objects in a washing macchine are pressed against the "wall"? I can experience the effects of the centrifugal force even if I am ...
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 ...
57 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 ...
92 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 ...
485 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 ...
180 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 ...
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-...
199 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 $B$ ...
584 views

### Motion of one body with reference to another

I studied that Galileo was punished by the church for teaching that the sun is stationary and the earth moves around it. His opponents held the view that earth is stationary and sun moves around it. ...
3k views

### How high do you need to be so as to not rotate along with Earth?

So, I saw this meme about some minister commenting that the Earth doesn't rotate, for if it did then planes only need to be in the air and the destination city would come to it. I know this is absurd ...
83 views

### Can an object take off from A, do not move (in the air) but land at a different place? [closed]

Can an object take off at a point A on the surface of the Earth and then land after some time only to land at a different place where it initially took off (because in the mean time the Earth has ...
262 views

### Momentum and relative motion

To calculate momentum, $p=mv$, you must know the value of $v$. However, since all motion is relative, there is no abslute value for $v$. So, what is it you are actually calculating? It seems like the ...
3k views

### What happens if you fly a drone inside moving passenger airplane? [duplicate]

I have a little question. If I mark an X in the center of a passenger airplane, and try to fly a drone from the X mark in the moving passenger airplane (800-900 km/h), what will happen to the drone? ...
The system consists of small mass $m$, large mass $M$, and chemical potential energy $E_{chem}$, as shown in below image, the reference frame is following the small mass throughout. The total energy ...