Questions tagged [rotational-dynamics]
A tag for questions about the mechanical interactions of rotating objects, including torque and angular momentum.
4,191
questions
132
votes
3
answers
6k
views
Why is the vibration in my wire acting so oddly?
I was soldering a very thin wire today, and when I had one end firmly soldered, I accidentally bumped the wire diagonally with my tweezers. What I'd expect to happen is that the wire oscillates for a ...
- 1,179
82
votes
7
answers
11k
views
Why is the Earth so fat?
I made a naive calculation of the height of Earth's equatorial bulge and found that it should be about 10km. The true height is about 20km. My question is: why is there this discrepancy?
The ...
- 53.2k
74
votes
6
answers
8k
views
Is there a way for an astronaut to rotate?
We know that if an imaginary astronaut is in the intergalactic (no external forces) and has an initial velocity zero, then he has is no way to change the position of his center of mass. The law of ...
- 840
66
votes
10
answers
21k
views
Why doesn't a bike/bicycle fall if going with a high speed?
Why does a bike/bicycle fall when its speed is very low or close to zero and is balanced when going with a high speed?
- 777
65
votes
7
answers
12k
views
Why does everything spin?
The origin of spin is some what a puzzle to me, everything spin from galaxies to planets to weather to electrons.
Where has all the angular momentum come from? Why is it so natural?
I was also ...
- 659
64
votes
12
answers
16k
views
Mathematically prove that a round wheel roll faster than a square wheel
Let's say I have these equal size objects (for now thinking in 2D) on a flat surface.
At the center of those objects I add equal positive angular torque (just enough to make the square tire to move ...
- 853
63
votes
15
answers
31k
views
Why does dust stick to rotating fan propeller?
Why does dust stick to rotating fan propeller?
Intuitively, most people (including I) think of the dust will not stick to rotating fan propellers.
- 2,699
60
votes
10
answers
44k
views
Why does a body always rotate about its center of mass? [duplicate]
I found after searching that this question has been asked before. But all the answers were not convincing.
Suppose I have a body which is free, not constrained always rotate about its center of mass (...
- 2,797
57
votes
8
answers
10k
views
Principle of physics used in the lift of skateboard
What is the principle of physics used in this popular stunt?
Initially, I thought aerodynamics due to an increase in the angle of attack, but its magnitude is not sufficient to balance the whole body ...
- 724
56
votes
8
answers
44k
views
Proof that the Earth rotates?
What is the proof, without leaving the Earth, and involving only basic physics, that the earth rotates around its axis?
By basic physics I mean the physics that the early physicists must've used to ...
- 563
51
votes
5
answers
21k
views
How do bicycle spokes work?
As you know, it is quite obvious that bicycle spokes attach the hub in the center to the rim. What else do they do? If you compare the wheels today with the ones from ancient times, there are more ...
- 1,107
48
votes
3
answers
8k
views
Why don't galaxies orbit each other?
Planets orbit around stars, satellites orbit around planets, even stars orbit each other. So the question is: Why don't galaxies orbit each other in general, as it's rarely observed? Is it considered ...
user98038
48
votes
12
answers
88k
views
What do people actually mean by "rolling without slipping"?
I have never understood what's the meaning of the sentence "rolling without slipping". Let me explain.
I'll give an example. Yesterday my mechanics professor introduced some concepts of rotational ...
- 4,634
48
votes
5
answers
3k
views
Intuition as to why the orientation (of a 3D object) is not a conserved quantity?
Say you start off floating in space, in a fixed position and orientation,
with zero linear and angular velocity, with no external forces.
So you are a closed mechanical system. By twisting your body ...
- 669
48
votes
1
answer
5k
views
Why does this object periodically turn itself?
See below gif image taken from here.
Or see this Youtube video about 30 sec in.
Is this a real effect?
Why does it seem to turn periodically?
Can it be explained by classical mechanics alone?
Is ...
- 515