The time derivative of angular position used when studying rotating objects or systems.
Questions tagged [angular-velocity]
846 questions
48
votes
5 answers
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 around,
you can't change your linear…
Don Hatch
- 737
29
votes
4 answers
Why are angles so weird?
I'm potentially asking quite a stupid set of questions here but I'm wondering if there is some overarching theory about why angles, and "rotational" quantities which deal with them, have such strange properties (to me - I might just have overthought…
krill
- 421
27
votes
2 answers
Is the speed of Earth's spinning constant over a given 24 hours?
Is the speed that the Earth spins on its axis constant over the course of 24 hours?
As opposed to does it turn faster and slower during different hours over any given day even by a very small variation. Who has made such measurements and how were…
JohnTrainor
- 481
26
votes
7 answers
How is it that angular velocities are vectors, while rotations aren't?
Does anyone have an intuitive explanation of why this is the case?
Casebash
- 2,804
23
votes
3 answers
Can the direction of angular momentum and angular velocity differ?
While studying rotational mechanics, I came across a section where it mentioned that angular momentum may not necessarily be parallel to angular velocity. My thoughts were as follows:
Angular momentum ($L$) has the relation $L=I\omega$ where…
Physicsapproval
- 585
22
votes
10 answers
How can I determine the rpm of a wheel that's spinning really fast?
Let's say that I have a motor that's spinning really fast. I really want to know the angular speed of the motor. Using a stopclock definitely won't work as no one can time such fast rotations. So how would I find the rotational frequency in such a…
Pritt Balagopal
- 3,237
21
votes
6 answers
Why is the velocity different for different points on a rolling wheel?
Lets take the following example
According to above examples it means that velocity at the above portion is max while the velocity at lower portion is min.
But I think it should be the same at both parts (just opposite in direction).
Why are both…
Junaid S.
- 313
18
votes
3 answers
Direction of angular velocity
Angular velocity is the rate of angular displacement about an axis. Its direction is determined by right hand rule.
According to right hand rule, if you hold the axis with your right hand and rotate the fingers in the direction of motion of the…
Rafique
- 1,199
18
votes
1 answer
Is Earth’s rotation slowing down or speeding up?
Section ‘Slowing down of the Earth’ of the Wikipedia article Leap second has the following paragraphs:
A mathematical model of the variations in the length of the solar day was developed by F. R. Stephenson and L. V. Morrison, based on records of…
Géry Ogam
- 281
18
votes
2 answers
Is the right hand rule a trick to avoid tensors?
I have read in this answer that
"to represent angular momentum as a vector you need to use a right hand rule. This is annoying, because physics at ordinary scales is reflection invariant but people do this to avoid tensors, because they have more…
veronika
- 2,867
16
votes
6 answers
How can the angular velocity vector be obtained from angular displacement which is not a vector?
My physics book (The Fundamentals of Physics) while explaining vector-ness of angular quantity (formally "Are Angular Quantities Vectors?") states that angular velocity and angular acceleration are vectors. But the turning point comes when it talks…
user249968
16
votes
1 answer
Effect of the tail of the cat in the falling cat problem
To explain why a falling cat can turn by 180 degree without external torque and without violation of the conservation of angular momentum, one usually models the cat as two cylinders as in
http://en.wikipedia.org/wiki/Falling_cat_problem
This may…
Julia
- 1,918
15
votes
4 answers
Why are angular mometum and angular velocity not necessarily parallel, but linear momentum and linear velocity are always parallel?
I have read that it's not necessary for angular momentum and angular velocity to be parallel, but it is necessary for linear momentum and linear velocity to be parallel. How is this correct?
may
- 187
15
votes
3 answers
Home experiments to measure the RPM of a pedestal fan without special equipment?
Is it possible to determine to an approximate degree, the revolutions per minute of a fan, for example a pedesal fan pictured below, without using some electronic/mechanical measuring device?
One thing that comes to mind is the markings on a old…
Zabba
- 253
14
votes
2 answers
Dynamics of counter-rotating flywheels
I've wondered about this for ages. If we create a pair of flywheels that rotate in the opposite direction with the same angular momentum, but are co-located and have the same mass and inertial moment (one can imagine various ways to accomplish…
user1055643
- 241