Circular motion about a central point or axis

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How do you rotate spin of an electron?

I can't seem to connect these two stories. Can you please help? I have heard that you have to turn electron by 720 degrees in order to get the same spin state. Has this been seen experimentally? How ...
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3answers
98 views

QM rotation operator

I have seen the proof that for fermions a rotation of $2 \pi$ does not return a spin angular momentum eigenstate to its original form, but instead multiplies the wavefunction by $-1$. Here is an ...
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2answers
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Half-integer spin and infinitesimal rotations

On p. 692 of 'Quantum Mechanics' by Cohen-Tannoudji, he states that: Every finite rotation can be decomposed into an infinite number of infinitesimal rotations, since the angle of rotation can ...
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1answer
36 views

Wheel slowing down with constant acceleration

A wheel of radius $R$ spins about its center with a centripetal acceleration of $v^2/R$. I get that the acceleration at all points on the rim of the wheel point towards the center of the wheel. But, ...
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0answers
27 views

Applying a Force on a non fix body [duplicate]

If we apply a force on a fixed body and if that body rotates, we calculate torque about that pivot point. But if that body is not fixed and then we apply force that provides translational motion and ...
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1answer
28 views

A fluid in a wide tube being centrifuged

Imagine a large, awkward and imbalanced centrifuge with the glass test tube in the shape of a large rectangular prism, rotating about one of its ends parallel to the sides. Inside this glass test ...
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1answer
40 views

Does the moment of inertia change?

I am currently working on a practice problem for my upcoming exam and I have difficulties getting my head around moment of inertia. If the ball has mass $m$ and is going around in a circle with ...
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0answers
30 views

What if you spin a fluid in one direction at center and at the same time opposite direction at outside?

This question keeps me busy for couple of weeks. To be clear, If I put a fluid into a blender and start it, it will spin in one direction. This will create a small vortex. What if I am able to spin ...
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0answers
31 views

Relation between two sets of generators of SO(3) [migrated]

I am working with the spin 1 representation of SU(2), which is just SO(3). The ordinary generators used in quantum mechanics are: $J_x = \left( \begin{array}{ccc} 0 & \frac{1}{\sqrt{2}} & 0 ...
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1answer
45 views

Euler angle rotation - active/passive

I have a very simple problem, that I cannot wrap my head around and is hurting my brain. I have a very simple example of the problem, please consider the the figure below: In the first picture, you ...
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0answers
54 views

How to get from momentum to force

Situation: I have a solid object (black) attached to a rod (blue) as shown below: The rod is fixed at the top. The solid object is a cylinder as shown, with a rate of rotation ...
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2answers
38 views

Can center of mass move without any force?

For instance, consider a weight on one end of the ring. Assume that the ring has negligible mass compared to the weight. When the weight splits into two, moves around the ring and recombines at the ...
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3answers
57 views

Newton's Second law of Rotation

In my book (Halliday Resnick Walker) there is a solved example which is as follows There is a uniform disk with mass $M$ = 2.5kg and radius $R$ = 20cm, mounted on a fixed horizontal axle. A block ...
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1answer
59 views

Physical interpretation of diffeomorphism from $SO(3)$ to $\mathbb R \mathbb P^3$

I am not good at picturing either $SO(3)$ or $\mathbb R \mathbb P^3$, the latter denoting the real projective space. Can someone give me a rough physical understanding of the geometry and implication ...
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2answers
61 views

How's equilibrium possible here?

Here's the question.......Two point masses $m$ and $2m$ are attached at each end of a light rod. The rod is pivoted at the center and is free to move in a vertical plane. Then find the angle $A$ when ...
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5answers
144 views

As a car turns around a circle, why does the force of static friction point towards the center of the circle [duplicate]

A car moves along a flat, circular road. It has a tangential velocity to the road, but the car tires change direction and the car experiences a force of static friction causing a centripetal ...
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2answers
59 views

Torque at a disc sandwiched between two rotating discs

I have a question in my mind regarding torque transfer taking place in the current situation. There are three rotation elements A, B & C as shown in the figure. The rotating element A is ...
3
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2answers
59 views

Physics of tidal locking: can the process be underdamped?

Is it possible for a satellite undergoing the process to overshoot the required rotation rate for tidal locking? For example, if its rotation rate is being slowed, can it become slower than it needs ...
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0answers
66 views

Why and how is acceleration absolute?

Is there a testable model which explains why rotation of an object in space and straight-line acceleration appear to be absolute while uniform translation is relative? I know of Mach's explanation, ...
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3answers
289 views

How does a rotating object cause frame dragging?

Frame dragging is a consequence of general relativity. But I don't really understand it. Of course I can find metaphors like the "honey metaphor" where stirring a honey can move the specks even if ...
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5answers
751 views

Rotation vs translation

What is so fundamentally different between a rotation and a translation that one can be represented with a single n-vector and the other one needs an n-n matrix?
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1answer
41 views

Rigid Body Dynamics - Calculating Rotation of an Object

I've looked everywhere and I can't quite find a concise answer, especially due to my limited knowledge and understanding of terminology. I found something called Rodrigues' Rotation Formula that ...
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1answer
57 views

How many times does the ISS celebrate New Year each year? [closed]

My question is, how many times each year do the crew of the ISS have an opportunity to celebrate New Year? Does it vary each year or will it be a fixed number? I tried to work this out for myself ...
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3answers
714 views

Does the Earth actually rotate around the sun? [duplicate]

Why does one say that the Earth rotates around the sun? There should be no preferred reference frame and from an observer on the sun, the sun will rotate around the Earth.
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2answers
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Is this a correct understanding of circular motion?

We say an object experienced uniform circular motion iff it moves in a circle of constant radius, with constant angular velocity. To experience uniform circular motion, must the net force on the ...
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1answer
24 views

inertial pressure on in a rotating syringe

First question on stackexchange. Hopefully somebody can help me out. I'm struggling to express the following eloquently. I have a rotating syringe tipped with a needle. rotation speed w, with radius ...
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1answer
34 views

Specific scenario involving rotation and inertial frames of reference?

We recently went over some rotational motion in my freshman physics class, I had a question for the professor on your frame of reference, and how that would effect the rotation of the object. Say you ...
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5answers
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Can a ultracentrifuge be used to test general relativity?

With today's ultracentrifuge technology, they can spin so fast that the sample can be subjected to accelerations of up to 2 millions Gs. That is equivalent to two solar masses. Has someone tried to ...
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0answers
73 views

Does non-rotating object have rotational inertia if it is attach to rotating object by a spring

My question relating to the Rotational Inertia as a whole system. As I learn that the Rotational Inertia is defined for a rotating object to an fixed axis but I got problem in the case a rotating ...
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1answer
48 views

Motion of a rigrid body: Why is motion only a compostition of two forms: rotation and Translation?

If you are in a 2-D space the motion of any rigrid body is composed of 2 different things, namely rotation and translation. If you are in 3-D space the motion of any rigrid body is also composed of 2 ...
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1answer
54 views

Ideal Rolling Motion on Surface with Friction

I have a question concerning ideal rolling motion on a surface containing friction. By ideal rolling motion, I mean the tangental velocity of the rolling object is the same as the velocity of the ...
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1answer
94 views

Can the angular momentum of any rigid body (symmetrical or asymmetrical) be found this way?

Can the angular momentum of anybody regardless of whether its symmetrical about the center of mass or not be found by finding the angular momentum about its center of mass and summing it up with the ...
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0answers
55 views

A particle attached to a string rotating around a cylinder seems to increase in energy. Does it? [closed]

When a particle attached to a string rotates around a cylinder of finite radius, a point on the curved surface of the cylinder to which the other end of the string is attached, the particle spirals ...
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2answers
111 views

Confusion with rotation operator definition in Shankar

In Shankar quantum mechanics on page 306-307 it has the following: 12.2. Rotations in Two Dimensions Classically, the effect of a rotation $\phi_0\mathbf{k}$, i.e., by an angle $\phi_0$ about ...
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1answer
50 views

Rotation in configuration space

Let $R_\psi$ be the rotation in configuration space around a vector $\bf{e}_\psi$ for an angle $\psi$. How is that the space rotation in configuration space have: ...
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1answer
49 views

Rotational Speeds

I was driving the other day and couldn't help but look at all the wind mills in the wind farms. I know I am not doing the math correctly, but I want to know what is "really" happening when a windmill ...
2
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1answer
60 views

Symmetries of the action of the free classical Klein-Gordon field

I've read that the action for the free classical Klein-Gordon field $$S = \int \mathrm{d}^4x~ \mathcal{L} = \frac{1}{2} \int \mathrm{d}x^4 \left(\partial_\mu \phi(x) \, \partial^\mu \phi(x) - ...
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1answer
144 views

Increase in kinetic energy as some one walks to the centre of a merry-go-round?

When someone walks to the directly centre of a merry-go-round the total kinetic energy of the merry-go-round and person system increases. (assuming the kinetic energy due to the person walking to the ...
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0answers
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Calculate rotational duration of magnetic levitation inside a vacuum chamber?

Background Numerous examples show rotating pyrolytic graphite (or similar diamagnetic material) that can be moved using a laser. Problem The problem has the following objects: An N52 grade ...
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1answer
106 views

How to model a very simple spinning wheel

First off, I'm not a physics person, just a lowly software engineer with below average math skills. What I've written is a simple animation of a spinning wheel using C++/GTK/Cairo. It allows the user ...
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2answers
235 views

Does a tire need to slip to generate force?

Recently, I have been doing some research on racing and tire modelling. While I was doing this, I encountered many curves like those shown below. While I understand the need of slip angles to ...
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1answer
46 views

Angular displacement after full rotation

I was wondering is why angular displacement isn't $0$ after $n$ full rotations?
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1answer
80 views

Rotating metal sphere

My knowledge of physics is not that great, but I am always willing to learn. I have the following question: If we have a sphere made out of metal with a radius of 1 meter, and it rotates in an ...
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0answers
59 views

Determining rotational period of sun using sunspots

I know that at the equator at 0 degrees latitude , you could track a sunspot and then use T=2pi/w and w=∆theta/∆t to work out the period the equator rotates, but how would you do it for, say, ...
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1answer
474 views

Instantaneous axis of rotation and rolling cone motion

Suppose a cone is purely rolling (no slipping) around a fixed axis. I mean, it is revolving around a fixed axis perpendicular to the ground and passing through its vertex and also rotating, so the ...
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3answers
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Can a rigid body have three independent rotations, about three different, mutually perpendicular axes?

It appears that this is kinematically possible, but it looks quite unprobable. For example, it is quite improbable for a sphere to have rotation about three mutually perpendicular axes (supposedly ...
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3answers
158 views

Two-rotation coordinate transformation

I've designed an electronic device that uses a 3-axis accelerometer to measure the acceleration of an automobile. I'm only interested in accelerations in the plane of the road surface, so I want to ...
2
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2answers
188 views

Does General Relativity correctly explain the ellipsoidal shape of the earth?

Does General Relativity theory correctly explain the ellipsoidal shape of the earth? It seems it does not because the Thirring expression¹ for the force of a spherical shell—of mass $M$, radius $R$, ...
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A particle is moving on a circular track with omega = 0.2926829268 rads/s. How many revolutions in 30s? [closed]

Physics HW Q: A particle is moving on a circular track with omega = 0.2926829268 rads/s. How many revolutions in 30s? What I have done: It seems to me that I must convert from rads/sec to ...
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1answer
81 views

In 2-dimensional and 3-dimensional universes, stellar systems and galaxies are flat and disky. But what about in 4-dimensional universes?

I just watched that interesting video: https://www.youtube.com/watch?v=tmNXKqeUtJM In 2 dimensions a cloud of particles rotating in a plane is flat by definition since it's in 2 dimensions. ...