The conserved quantity arising from a rotational invariance. Combine with rotational-dynamics for the classical mechanics approach and quantum-mechanics for the QM interpretation

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How can a point-particle have properties?

I have trouble imagining how two point-particles can have different properties. And how can finite mass, and finite information (ie spin, electric charge etc.) be stored in 0 volume? Not only that, ...
4
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1answer
404 views

Angular momentum in string theory

Since strings are extended objects, is all angular momentum in string theory essentially "orbital" angular momentum? Or is there still a kind of intrinsic angular momentum assigned to a string? ...
8
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2answers
885 views

Intrinsic angular momentum in classical mechanics

Please note, I am only interested in classical mechanics discussion on this. Please do not involve quantum mechanics. Inspired by this question: Is Angular Momentum truly fundamental? My question ...
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2answers
1k views

Mech stability through gyroscope

I recently read up about gyroscopes, angular momentum and mechs (the big Cockpit controlled robots) and was wondering if it would be possible to get a stable walking mech (only as example, not meant ...
1
vote
0answers
152 views

Will earth rotation be slowed down? [duplicate]

Possible Duplicate: Are tidal power plants slowing down Earth's rotation? Since we have various energy acquiring facilities that harvest energy from earth rotation. (e.g. wind, tidal ...
5
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1answer
867 views

Angular momentum and EM wave

Is there any sense in saying that circularly polarized EM waves have angular momentum?
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3answers
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How does Newtonian mechanics explain why orbiting objects do not fall to the object they are orbiting?

The force of gravity is constantly being applied to an orbiting object. And therefore the object is constantly accelerating. Why doesn't gravity eventually "win" over the object's momentum, like a ...
2
votes
1answer
940 views

Does ABS cause a force that resists turning a car into a corner?

ABS systems work by allowing a tire to continue to rotate rather than "locking-up" (stop turning) due to loss of traction with the road surface. A rotating tire can influence the direction of the ...
3
votes
2answers
1k views

Dynamics of moment of inertia

I'd like to be able to determine the angular acceleration of a system of two rotating masses, which are connected so as to have a variable mechanical advantage between the two. My background with ...
2
votes
3answers
636 views

How long for a frictionless top to fall over?

We've previously discussed why it is that spinning tops do not fall over, see: Why don't spinning tops fall over? However, as the highest rated answer notes, the angular momentum of the spinning top ...
2
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2answers
568 views

Homework about spinning top [closed]

I have a top of unknown mass that has a moment of inertia $I=4\times 10^{-7} kg \cdot m^2$. A string is wrapped around the top and pulls it so that its tension is kept at 5.57 N for a distance of .8 ...
1
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1answer
223 views

Interaction of polarized beam to optical active substance

Kostyas question for angular momentum and half wave plates Half wave plate and angular momentum made me think a little bit. It took me some seconds to "swallow" the answer. :=) Then I started to ...
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2answers
701 views

Half wave plate and angular momentum

Given: A half wave plate freely floating in space. Circularly polarized light, falling perpendicularly to it. The plate changes polarisation of the beam to the opposite one. Therefore it ...
2
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3answers
2k views

Could life survive a pole shift caused by an asteroid collision?

Could life on earth survive a large pole shift caused by an asteroid collision? I became aware that there are people who believe that the earth's pole suddenly shifts. That is, its rotational ...
8
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2answers
471 views

Addition of Angular Momementa in deeply bound situations, proton spin crisis

In Landau and Lipshitz's introductory book on Quanum Mechanics, "Quantum Mechanics Non-Relativistic Theory, Third Edition: Volume 3", chapter XIV (page 433 in the edition on Amazon) is "Addition of ...
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5answers
20k views

Why does a ballerina speed up when she pulls in her arms?

My friend thinks it's because she has less air resistance but I'm not sure.
9
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1answer
1k views

Why do galaxies and water going down a plug hole spin?

We all experience things spinning, whether it's water down a drain, the earth on its axis, planets round the sun, or stars in a galaxy - even electrons round an atom. But why is spin so common in ...
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votes
6answers
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Rotation angle of a giant lily when a child crawls on its rim

Below is a picture of Giant Water Lily. Scientific Name: Victoria Amazonica. Leaves of some of these could be as big as 3 m diameter and carry a weight of 45kg spread evenly and can support a child. ...
10
votes
6answers
2k views

Why does a curling rock curl?

In the game of curling, players "curl" a granite "rock" (of precise size and roughly a flattened cylinder) down a "sheet" of ice towards a target; the "rock" will curve in its path in the direction of ...
10
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1answer
3k views

Why exactly does a boomerang return back to the thrower?

I was always intrigued by the phenomena that govern the returning back of a boomerang to the thrower. Even if it is dependent on various factors such as velocity, aerodynamics, wind resistance and ...
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5answers
4k views

What if the universe is rotating as a whole?

Suppose in the milliseconds after the big bang the cosmic egg had aquired some large angular momentum. As it expanded, keeping the momentum constant (not external forces) the rate of rotation would ...
64
votes
9answers
6k views

Is Angular Momentum truly fundamental?

This may seem like a slightly trite question, but it is one that has long intrigued me. Since I formally learned classical (Newtonian) mechanics, it has often struck me that angular momentum (and ...
-1
votes
2answers
5k views

Period of Precession [closed]

I'm trying to find the period of precession for a gyroscope. Now I was able to find the angular precession rate, which was 1.132 rad/s, but I have no idea how to convert this to a 'period', and google ...
0
votes
2answers
328 views

Angular Momentum and Force [closed]

I'm stuck on number 5. The answers to the first 4 are correct, but I dont know how to set up number 5. Any idea that I would have would require me having some kind of time information, but thats not ...
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2answers
3k views

Angular Momentum and Average Torque

Refer to number 6. This is the one I'm stuck on. So angular momentum is conserved right, so initial angular momentum is equal to final angular momentum. Initial is 7.87 so final must be 7.87, right? ...
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7answers
8k views

Why don't spinning tops fall over?

One topic which was covered in university, but which I never understood, is how a spinning top "magically" resists the force of gravity. The conservation of energy explanations make sense, but I don't ...
2
votes
1answer
804 views

acceleration of rings in aerotrim (human gyroscope)

I'm working on a graphic simulation (just for fun, for an open-source screensaver) of an Aerotrim - a "human gyroscope", one of those exercise/training machines with a human in the middle, perched on ...
49
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4answers
7k views

What is spin as it relates to subatomic particles?

I often hear about subatomic particles having a property called "spin" but also that it doesn't actually relate to spinning about an axis like you would think. Which particles have spin? What does ...