The rotation tag has no wiki summary.
2
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1answer
42 views
Who has succeeded in demonstrating the Lense-Thirring effect?
Who has succeeded in demonstrating the Lense-Thirring effect?
This effect is one that describes the rotational motion of the Earth from a space-time structure. This effect is the "drag" of the ...
7
votes
3answers
468 views
Shape of rotating rope (lasso problem?)
Let's take a wire or a rope. I usually do this with a chain or my scarf.
I fixate one end in my hand and apply rotation (by subtle movements of this endpoint like spinning a lasso). The rope gets ...
3
votes
1answer
164 views
What's a pseudo-rotation?
I'm sorry for this lexical, probably extremely elementary, question. But what is a pseudo-rotation? I just read this term for the first time, in the beginning of the 4th chapter book of CFT by Di ...
1
vote
3answers
339 views
Does being suspended in air allow you to not be affected by Earth's rotation?
Let's assume that there was some mechanism by which we could remain suspended in air. By this I mean that our feet is not in contact with the ground. One possible way of doing this would be by means ...
2
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1answer
85 views
Synchronising the Earth's rotation via mass redistribution
How much material would have to be moved per year from mountain-tops to valleys in order to keep the Earth's rotation synchronised with UTC, thus removing the need for leap seconds to be periodically ...
3
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2answers
57 views
Can a minimum ultimate tensile strength (UTS) for an asteroid be established based on its diameter and rotation?
I found it fascinating that many asteroids rotate with a period of just seconds. For this fast of a rotation on this size of object, I thought that would actually cause significant acceleration on the ...
1
vote
2answers
688 views
Will a boiled egg or a raw egg stop rolling first?
If we roll a normal egg and a boiled egg at the same time on a floor
1) with friction
2) without friction
which one will come to stop first (if they will stop at all) and why?
Can anyone tell ...
4
votes
4answers
924 views
Two axes for rotational motion
I understand that angular momentum is a vector, etc..
But, what really happens when some object, say a ball for example, is set to rotate along two axes? What would the resulting motion look like?
2
votes
1answer
180 views
What “I” should use in Rotational Energy formula $(I \omega^2)/2$
$\text{Rotational Energy} = \frac{1}{2} I \omega^2$. What $I$ should be used?
$I$ as a inertia tensor matrix = stepRotation * inverse moment of inertia * inverse stepRotation;
Or I as moment of ...
5
votes
6answers
550 views
Why does the earth rotate? [duplicate]
Possible Duplicate:
Why does every thing spin?
So why would the earth, or any planet for that matter, rotate along an axis? I know of no force which could come into play here, so i assume ...
1
vote
1answer
162 views
Finding stopping time when only given initial angular velocity and an expression for angular acceleration?
Question:
A wheel starts is spinning at $27\text{ rad/s}$ but is slowing with an angular
acceleration that has a magnitude given by $\alpha(t) = (3.0\;\mathrm{rad/s^4})t^2$. It stops in a time ...
1
vote
0answers
137 views
Error caused by pulley eccentricity [closed]
Not sure if this is perfectly a physics question:
A rope is wrapped around a cylinder of diameter D. The cylinder is slightly eccentric so that the distance between the axis of the cylinder and the ...
7
votes
4answers
8k views
Does the rotation of the earth dramatically affect airplane flight time?
Say I'm flying from Sydney, to Los Angeles (S2LA), back to Sydney (LA2S).
During S2LA, travelling with the rotation of the earth, would the flight time be longer than LA2S on account of Los Angeles ...
7
votes
4answers
400 views
Why does a ping pong ball change direction when I spin it on a table?
When I spin a ping pong ball on the table, it rolls forward in the opposite direction of the spin, and then eventually changes direction and rolls backward.
Here's a video demonstrating the effect.
...
13
votes
1answer
644 views
Which way do spiral galaxies rotate?
Is it known whether spiral galaxies typically (or exclusively?) rotate with the arms trailing or facing?
Intuitively it feels weird to think of the arms as facing the direction of rotation, but ...
2
votes
4answers
347 views
why does what get pushed away when centripetal acceleration is towards the center
If centripetal acceleration is towards the center, then why - when you spin a bucket of water (a classic demonstration) - does the water not get pushed out but rather stays in the bucket without ...
5
votes
4answers
657 views
Video of Earth spinning?
If the Earth is spinning or rotating at a really fast speed, why haven't we seen any videos from space of it spinning when we get a lot of photos of it?
8
votes
4answers
3k views
Are there planets that do not rotate on their axis?
I was reading a thread about how a pendulum would be affected if the Earth did not rotate and Larian's answer made me wonder if all planets rotate necessarily due to physics.
So that's the question: ...
9
votes
1answer
277 views
If the Earth didn't rotate, how would a Foucault pendulum work?
How does the Foucault pendulum work exactly, and would it work at all, if the Earth didn't rotate?
2
votes
2answers
517 views
Formula for Rotation curves of Galaxies
To ask a more specific one for the rotation curves of elliptical galaxies, and hope from there to later understand the dynamics of spiral galaxies.
Treating the galaxy as an isothermal ...
3
votes
3answers
1k views
MEMS gyroscope and orientation
I'm trying to understand how a MEMS gyroscope can give you orientation. The question may not make any sense, I may have some misunderstandings about the different topics...
From the wikipedia page ...
0
votes
1answer
162 views
What are the known relationships between rotation of planets/moons and their distance to Sun?
What are the known relationships between rotation of planets/moons and their distance to Sun? Or any other known attributes? For example, the sidereal year for planets is directly related to their ...
3
votes
1answer
67 views
What exactly is the definition of motion and its relation to Mach's conjecture?
The notion of "movement" seems to be well understood in physics. In fact, I don't recall any physics text-book defining motion. Special relativity theory says that there is no absolute frame of ...
2
votes
1answer
416 views
Help understanding a Magnetic Levitation “Physics Toy”
I was shown a toy, yesterday, which I would like help understanding qualitatively.
A fellow engineer showed me a kit which included three main parts:
1.) A base (black box), approximately 4 ...
1
vote
2answers
218 views
Doubt concerning centripetal acceleration
What is the centripetal acceleration and angular velocity of a child located 8.2 m
the center of a carousel? The speed (size of the tangential velocity) of the child is
2.1 m / s
A train moves in a ...
6
votes
3answers
84 views
What frame(s) of reference are used to measure the rotation of the Sun around the galaxy ?
I can find various speeds and estimated durations listed at numerous places but none specifically describe the frame of reference.
Possible options as example of kind of answer I expect.
Local ...
-3
votes
1answer
130 views
How can the Earth's day increase and its rotation slow down at the same time? [closed]
I heard that the Earth rotation is slowing down, but I also heard the Earth's length of day is increasing.
Does the two theories go together or conflict with each other?
12
votes
3answers
557 views
Why does each celestial object spin on its own axis?
AFAIK all the celestial objects have a spin motion around its axis. What is the reason for this? If it must rotate by some theory, what decides it's direction and speed of rotation?
Is there any ...
8
votes
5answers
875 views
How is it that angular velocities are vectors, while rotations aren't?
Does anyone have an intuitive explanation of why this is the case?
