A specific reference frame that describes its coordinates in a manner that does not depend on time and is isotropic.

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3-body system centre of mass

I have a three body system of point masses that represent mercury, earth and the sun. I want them to orbit about a common centre of mass, but I think the centre of mass will move. I need the centre of ...
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1answer
49 views

How to find the magnitude of electric and magnetic fields in an arbitary inertial frame?

In the context of special relativity, and using proper Lorentz transformations: If the electromagnetic fields have an uniform value [= constant in space and time] in an inertial frame, how will the ...
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40 views

How would you prove/verify that the real forces are independent of frame of reference?

How would you prove/verify that the real forces are independent of frame of reference?
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1answer
67 views

Difference between first newton's law and second newton's law ? [duplicate]

the first and second laws of newton are both similar, so why do we need the first law if it is the same as the second? what is the big difference between these?
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3answers
80 views

How would you explain the weight of an object in a lift accelerating up with acceleration a?

Observer in the lift:- He is unaware of his acceleration. He applies Newton's second law and got N = Mg. After that he used spring balance and found that the wait of the object is M(g+a). So to ...
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2answers
71 views

Minkowski geometry definition

The general relativity is based on Minkowski geometry definition with its special properties. The general relativity cant be approved wihout Minkowski geometry definition. Why Minkowski geometry is ...
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1answer
63 views

Given the 1st Postulate of SR, doesn't the 2nd Postulate go without saying? [duplicate]

i've been looking over possible duplicates of this question and haven't found one yet. so, using Wikipedia as the textual source: The Principle of Relativity – The laws by which the states of ...
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1answer
78 views

How to prove that “all unaccelerated frames behave likely for all isolated bodies”? [closed]

Say in an unaccelerated frame "S" a "isolated body A" moves with constancy of velocity , can we predict mathematically that any other such body B will move with same velocity in that frame.... My ...
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1answer
83 views

A fast object (0.8c) getting overtaken by another fast object (0.9c): why don't times agree?

I'm trying to work on an exercise in Wolfgang Rindler's book "Introduction to Special Relativity" and I'm stuck on the following exercise: Two particles move along the x-axis of S at velocities ...
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4answers
502 views

Gravity between two unequal masses. Do both masses move?

I've been watching videos about gravity and I have a question My understanding is that mass have gravity and gravity is a force which attract other object with mass. For example, I jump up and the ...
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0answers
39 views

Biological concept behind time dilation [duplicate]

What is the exact mechanism which makes aging process slow for persons travelling at higher velocity relatively. How does our body cells responds to gravity and undergo aging?
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2answers
53 views

Do all moving object appear contracted?

In the derivation of Lorentz contraction my prof considered a rod moving away from you with speed $v$. In this case the rod appears shrunk by a factor gamma. But now let's consider a rod moving ...
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1answer
63 views

Why does Goldstein's derivation of orbits from Newton's law not yield the orbit consisting of symmetric oscillation along a line thru center of Sun?

Why does Goldstein's derivation of Keplerian orbits from Newton's law of gravity not yield the orbit consisting of symmetric oscillation along a line passing thru the center of the Sun? The fact that ...
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3answers
153 views

What does Newton's first law of motion want to say? [closed]

Newton's first law of motion says "A body will remain in a state of rest or in uniform motion in straight line, unless acted by an external force." So if a body is accelerated or moved ...
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5answers
76 views

Static model of the Earth motion

Believe it or not, an old man I know in 2015 still negates the Earth orbital motion around the Sun. He believes the earth is rotating on itself and acknowledges this gives day and night on every ...
2
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2answers
126 views

Why Earth is considered to be an inertial frame? [duplicate]

Earth rotates about its axis and also revolves around the Sun at the same time. So why Earth is considered as an inertial frame in Newtonian Physics. So technically, I'm effectively asking why the ...
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1answer
27 views

How to spatially rotate the frame of reference Faraday Tensor? Special Relativity and Galilei Transforms

Hey I'm currently just starting out doing special relativity and I stumbled upon following problem: If I have the faraday antisymmetric tensor $F^{\alpha \beta}$ and I perform a spatial rotation of ...
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2answers
61 views

Will my mass increase in my perspective while approaching near the speed of light?

Suppose I start my journey by a spaceship accelerate the velocity to 0.7c from Earth. Now the question arises that- Will my mass increase gradually as I'm going to a speed of .7c in my perspective and ...
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2answers
48 views

Where does the energy required to speed the object in this question come from if the object actually slows down from another perspective?

I was thinking about mechanics and energy and stumped myself with this scenario I made up: Suppose you are in a room and you are motionless. In the same room, a 1 Kg ball is moving to your right with ...
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0answers
28 views

Why is the speed of light constant in all inertial frames? [duplicate]

I know this is a physical principle and cannot be derived at from other physical laws. But how can it be arrived at? What observations or what train of thoughts leads to this conclusion? e.g. the ...
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1answer
236 views

Do free falling observers see gravitational blueshift?

Observers at rest in gravitational fields will see infalling light signals as blueshifted. Do inertial observers in free fall in a gravitational field see the same shift? If someone is standing on a ...
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1answer
83 views

Law of inertia, Frames of reference

Ok, we all know that an Inertial frame of reference is defined like this: "An inertial frame of reference is one frame where Newton's First Law holds, therefore, a body has a constant velocity or ...
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1answer
43 views

Isotropic of Inertial frame?

My understanding of isotropic is the a particular physics law remain same no matter at what direction I look at it? Now suppose in case of inertial frame, we know that its is homogeneous and ...
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1answer
35 views

Will the object spin as the earth spins?

If an object is designed to levitate a few kilometers above the ground, and the point directly below the object on earth is called $A$, as time passes and the earth rotates about its axis, will the ...
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2answers
41 views

Frames of Reference in a Rotational System

Imagine two concentric rings with different diameters. One is spinning within the other. There is a small gap between the outer diameter of the inner ring and the inner diameter of outer ring. From ...
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1answer
185 views

Spring rotated in uniform circular motion

Why does a spring stretch when rotated in uniform circular motion? The horizontal rod containing the massless spring(stiffness = k) and block of mass 'm' is rotated uniformly about point P. ...
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1answer
65 views

Contradiction of total energy of a system? [duplicate]

I consider a situation in a system in which an observer is sitting in body of mass $M$ and another observer in a body of mass $2M$, both moving with velocity $v$ towards each other. If observers in ...
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0answers
66 views

Is there an absolute accelerated frame of reference?

I know from special relativity and from a little common sense that there is no absolute inertial frame of reference; that is, physics acts the same no matter what velocity you go at. However, that ...
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1answer
97 views

Determining the velocity of an inertial frame of reference

Back in grade 12 I was told by my physics teacher that one would have no way of determining the velocity of an inertial frame of reference without comparing it to another (e.g. if a person was in a ...
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3answers
334 views

Are Newton's laws followed in non-inertial frame of references having all their objects and observer moving with same acceleration?

Consider a hypothetical scenario. In our universe there are two merry-go-rounds 1 and 2 and a distant planet. There is no other object having mass. There is a robot X on the planet. There are two ...
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4answers
111 views

How does light travel?

How does light travel, does this not contradict the idea that going the speed of light stops time? Because if going the speed of light stops time and light goes the speed of light shouldn't it be ...
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0answers
94 views

Is temperature a frame dependent quantity? [duplicate]

The temperature of an object is proportional to the average kinetic energy (1/2*m*v^2) of its particles (or molecules), then shouldn't the temperature depend on the frame of reference since v^2 will ...
2
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1answer
195 views

Centrifugal force on a pendulum

Why don't we consider the centrifugal force acting on the bob of a pendulum while drawing the Free Body Diagram of a pendulum? It's also a sort of circular motion.
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2answers
72 views

Does it take less time to drop a ball than fire one horizontally (with $90^{\circ}$) [closed]

So I was arguing about this with my friend. If we take two balls and drop one from a certain height H and then fire another one with horizontally with some initial speed from the same height H, which ...
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4answers
627 views

Stone dropped from a moving train

This may look like a stupid question, but it is really getting to me. Imagine a train moving with an acceleration $a$, and a person drops a stone from the window. To an observer on the ground, the ...
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2answers
71 views

Taylor's “Classical mechanics” - inertial balance

I am currently reading John Taylor's "Classical Mechanics" book and I am wondering how does the inertial balance work (as explained in figure 1.2, page 10). The autor says about an inertial balance ...
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5answers
590 views

Twins Paradox - Does ageing depend on motion?

I am trying to understand the Twins Paradox (relativity) and its implications. Can we infer from the Twins Paradox that the ageing process (cell decay or other biological processes) depends on ...
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2answers
585 views

Can a pilot in a small spaceship feel G force in space?

I am not really good in physics so I might be wrong at some points, but here is the situation. Consider a spaceship of the size of a fighter plane. And like a fighter plane, the ship is very mobile. ...
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3answers
283 views

Fundamental paradox with Newton's Law of Gravity?

This is my first post here, but I've been struggling with this problem in my head since I studied physics at school when I was 14 (30 years ago!). There seems to be a fundamental paradox with ...
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2answers
79 views

Shape and even connectedness of accelerating components in SR is frame dependent?

In some inertial frame consider a disk of radius 1 lightyear at rest. Then along the edge of the disk there are some people in spacesuits at rest hovering right above the disk (which has negligible ...
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2answers
85 views

Derive the velocity-additon formula from the Lorentz transformation

In a Euclidian world the sum $s$ of two velocities $v$ and $u$ is so such that $s = v + u$. However, in the world of special relativity that's not the case. Instead, the velcity vector sum $s$ is ...
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1answer
95 views

Time dilation and relativity paradox? [duplicate]

I've come across a weird paradox that I can't answer, I will explain it via the following thought experiment: There is a space-train and an observer 1 light year apart with synchronised clocks. The ...
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1answer
72 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 ...
2
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2answers
234 views

Two sets of coordinates each in frames $O$ and $ O' $ (Lorentz transformation)

Suppose inertia frame $O'$ is moving at velocity $v$ relative to inertia frame $O$. Let the coordinate systems of $O$ be denoted by $(x,y,z)$ and the corresponding one on $O'$ be denoted by ...
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3answers
145 views

Lorentz Transformations understanding

I am wondering whether or not I fully understood what the variables represent in the Lorentz time and distance transformations. What I understand is: t′ is the 'proper time', the time taken to move ...
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3answers
357 views

A question in Special Relativity

In books the equation for length contraction is derived by supposing that the velocity of the spacecraft is the same for both observers. So the question is that, is the velocity really the same for ...
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3answers
224 views

Why can't we find a true inertial frame?

From one book, I read that if we release a ball horizontally on earth, its velocity does change in very accurate observations. If we track its motion, we get full information of its motion (incl. ...
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2answers
603 views

What does the first postulate of specially relativity really say?

I know these two versions of the same postulate is saying the same thing. But I failed to connect them. Please help me understand the links between them. version1 The laws of physics are the same ...
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1answer
138 views

Problem conserving 4-momentum at CoM frame in an inelastic collision [closed]

I am confused about the case where mass is not conserved in a collision (not due to relativistic factors). The center of momentum (CoM) frame is not the same before and after the collision. Let's ...
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2answers
93 views

Energy in the Relativistic COM Frame

I have been taught that in Classical Mechanics, the total energy of a system of two particles in the Centre of Mass Frame is given by $$ E_\mathrm{total} = \frac{1}{2}MV^2 + \frac{1}{2}\mu v_r^2 $$ ...