Questions tagged [rotation]

Circular motion about a central point or axis

Filter by
Sorted by
Tagged with
-3
votes
0answers
41 views

Which of the following is not conserved ( for the following options) [on hold]

A smooth tube of certain mass is rotated in gravity free space and released. The two balls shown in the figure move towards ends of the tube. For the whole system which of the following quantity is ...
0
votes
0answers
12 views

Recent/More accurate rotation velocity measurement?

I've been researching for papers for hours and can't seem to find this. Where can I find the most accurate equatorial rotational velocity measurement for Mars?
1
vote
0answers
133 views
+100

Ray Tracing and Rotations

I would like to be able to write the matrix operations to be able to define the first arm of the picture below. How can I do that? I have learned beam physics, have read Siegman's Lasers, if that ...
2
votes
1answer
85 views

Are there physical quantities constitute of magnitude, direction and rotation along that direction?

There are scalar quantities(magnitude) and vector quantities(magnitude and direction), but are there fundamental quantities that also depends on how it's oriented/rotated along the direction(magnitude,...
1
vote
0answers
37 views

Spacetime rotation matrix using mostly minus conventions

When trying to find the Lorentz transformation in matrix form in the $x^2+x^3$-direction, I tried simply mapping the Lorentz boost in the $x^2$-direction to the $x+x^3$-direction by rotating it $45°$ ...
1
vote
1answer
42 views

Is there an easy way to tell whether this “Curlmeter” would rotate or not?

Let us say we have the following symmetrical apparatus: Four equal positive charges, all connected to a shaft that can rotate, the connecting rods are insulated, and so does the shaft. Now ...
0
votes
1answer
26 views

A thin rod is standing on a smooth surface [closed]

A uniform thin rod of mass m and length l is standing on a horizontal surface. A slight disturbance causes the lower end of the rod to start falling. find the velocity of the centre of mass of the rod ...
3
votes
1answer
130 views

Will an object dropped from a high building displace due to the Earth's rotation?

I read that in the 16th and 17th century, the question of whether the Earth rotates around its axis or all celestial bodies rotate around it was extensively debated. One of the anti-rotation arguments ...
0
votes
2answers
56 views

Why does twisting make it easier to remove a lid with a seal?

I have a pot with a lid that has a rubber seal (not a screw cap). When taking the lid off, it is incredibly difficult to lift the lid by pulling straight up on it, but twisting the lid whilst pulling ...
1
vote
2answers
45 views

Emergence of rotational symmetry on 2D square lattice

On page 74 of David Tong's Statistical Field Theory lecture notes, it is said that $(\partial_1\phi)^2 + (\partial_2\phi)^2 $ respects both $D_8$ (that includes discrete four-dimensional rotation ...
1
vote
0answers
31 views

How many illusionary axes of rotation can coexist?

Consider the answer to this question: How many different axes of rotation can coexist? Any rigid body, at any time, can only be rotating about one instantaneous axis of rotation. Now, that ...
0
votes
1answer
54 views

The Lorentz Transformation of the electric field of a moving charge

If I have a moving charge observed in frame $S$, may a Lorentz boost from $S$ in a direction not parallel to the charge's velocity in $S$ result in an electric field that has a different magnitude of ...
0
votes
0answers
14 views

Libration vs. rotation for mass on rotating disc

Hello I have a question about the difference between rotation and libration. In some textbook it is stated that for libration \begin{equation} q (t+\tau) = q(t) \\ p (t + \tau) = p(t) \end{equation} ...
0
votes
0answers
22 views

Velocity composition effect of moving line charges acting on a moving charge - By what velocity (boost) is the E-field unchanged along the boost?

Claim 1) An infinitely long line current can be modeled as the linear superposition of two infinitely long line charges. Claim 2) An infinitely long line current can exert forces on charges with ...
0
votes
0answers
25 views

Finding the total rotation about an arbitrary axis

I have a rigid body which is fixed in a x,y,z system and is free to rotate. The z vector is parallel to gravity. x and y are arbitrary and perpendicular to z. The moving coordinate system is x',y',z' ...
0
votes
2answers
34 views

Are the tides scale independent?

What I mean is the following. Imagine two smooth massive spherical bodies ($M_1\neq{M_2}$), with equal and homogeneous mass densities. Both masses have a layer of water on them for which holds ($R_1$ ...
1
vote
1answer
37 views

Electromagnetic field of a point charge seen from a rotating reference frame

Let us consider a point charge sitting in the origin of our coordinate system. If we change to a rotating system, will the field of the point charge still look the same? Intuitively I would say yes, ...
0
votes
0answers
26 views

Transformation of dielctric constant tensor

I have a dielectric tensor $$K = \begin{pmatrix} 2000 & 0 & 0 \\ 0 & 2000 & 0 \\ 0 & 0 & 50 \end{pmatrix};$$ which I want to transform to a new coordinate system given by ...
1
vote
1answer
28 views

Rotating coordinate frame connection of coordinates and mass

Hello I am still confused about rotating coordinate frames and want to ask a question about it. Is it correct that strictly speaking the mass must be connected with the axis of rotation in the ...
2
votes
6answers
572 views

Acceleration in circular motion

Can motion of a particle be circular if the radial acceleration is zero, but the tangential acceleration is not $0$?
1
vote
1answer
77 views

Change of reference frame for a wavefunction: same modulus but different currents?

Suppose that, at a certain $t=0$, one has a wavefunction $$ \psi=\psi(x,y) $$ defined on a plane and well normalized to $1$. Coordinates (x,y) refer to the frame $xOy$. How does the wavefunction ...
0
votes
0answers
23 views

Vorticity - Rankine vortex: how can we say that $\frac{\partial u_\phi}{\partial z} = 0$

\subsection{a} A Vortex formed in a bathtub, tornado or in other real world scenarios, exhibit nearly a solid body rotation in the core while far away from the center the flow is irrotational. This ...
1
vote
2answers
111 views

Griffith's Electrodynamics problem 1.9 (rotation through (1,1,1))

I was compiling some solutions to Griffith's E&M, and I can't get my solution to square with the others I have found online. The question asks: 1.9 Find the transformation matrix R that ...
0
votes
1answer
24 views

Conservation of Angular momentum or Work = 0 , which is valid?

In the figure, the block on the smooth table is set into motion in a circular orbit of radius "r" around the Center hole. The hanging mass is identical to the mass on the table and remains in ...
1
vote
2answers
55 views

Rotating coordinate frame

Hello I have a question about rotating coordinate frames. Following the book of Brizard the Lagrangian is given by \begin{equation} L(\mathbf{r}, \mathbf{\dot{r}}) = \frac{m}{2} \vert \mathbf{\dot{r}} ...
0
votes
2answers
85 views

What is a rotation group and how do we get its unitary representation?

The rotation group is ${\rm SO(3)}$. It is the group of $3\times 3$ orthogonal matrices $\{g(\theta)\}$ with unit determinant. So these are already defined in terms of $3\times 3$ matrices. But we use ...
1
vote
2answers
45 views

Angular momentum as an operator on triple product space

General arguments about introduction of angular momentum to QM is that under a transformation of coordinates the x and y position operators mix (as it is usually written) $$\hat{x}' = \cos(\theta) \...
1
vote
1answer
83 views

Parametrizing $SU(2)$ with Hermitian matrices

There is something that is not clear to me Here is what I know: Pauli matrices are $\sigma_1 = \begin{pmatrix}0 & 1 \\ 1 & 0\end{pmatrix}$, $\sigma_2 = \begin{pmatrix}0 & -i \\ i & 0\...
0
votes
4answers
77 views

A rod rotating about a pivot

A long, uniform rod of length L and mass M is pivoted about a frictionless, horizontal pin through one end. The rod is nudged from rest in a vertical position as shown in figure. At the instant the ...
0
votes
0answers
27 views

Does acceleration of the rim mean just tangential or both tangential and centripetal acceleration?

On my physics homework, the problem specifies that the acceleration of the rim of a flywheel can't exceed 100g. Does this mean that the tangential acceleration only, or the sum of the tangential and ...
0
votes
2answers
33 views

Point of application of tangential velocity in rotational motion

The tangential velocity of a particle in a rigid body is given by: $\vec{v}=\vec{\omega}\times \vec{r}$. Since the cross product is perpendicular to both $\vec{\omega}$ and $\vec{r}$, the velocity $\...
0
votes
0answers
30 views

Single number to quantify difference between two local reference frames?

I'm working with some satellite data that defines the spacecraft reference frame from two star cameras and two different measurements of orientation configuration of the cameras, and I'm trying to ...
1
vote
0answers
24 views

How to properly align my relaxed molecule onto my gold electrode?

the question is described below since it can be considered a chemistry or physics question: How to translate from one plane to another? originally posted on mathematics SE I am trying to get ...
2
votes
3answers
94 views

What is wrong with this reasoning?

Suppose a particle is rotating about a point at a distance $r$, then since $r$ is constant $\frac{\text dr}{\text dt}=0$ so the component of velocity along the position vector should be zero. ...
0
votes
1answer
36 views

Rotation of object at different positions

Why do object placed in a river rotates at different position when object is in center of flowing river it just moves forward but when it is on either side it rotates and moves forward what's the ...
1
vote
1answer
46 views

Earth rotation with atmosphere

Note: This might be a very dumb question Considering Earth's rotation on its axis, I was thinking it made sense for the outer sides of the Earth to have a significantly higher tangential speed, ...
0
votes
0answers
18 views

Producing Yaw (Orientation)

I am working with a car and trailer model which has a GPS sensor attached and I am looking for ways to calculate it's yaw (orientation). One way I am working on is two resolve both the car and ...
4
votes
3answers
146 views

Three spin states of a spin-1 particle

For a spin-1 particle at rest, it has three spin states(+1, -1, 0, along the z axis). If we rotate the z axis to -z direction, the spin +1 state will become the spin -1 state. Can we transfer the spin ...
8
votes
2answers
204 views

How to infer that the black hole in M87 is rotating clockwise?

The spokesperson mentioned that the rotation of M87 supermassive blackhole is rotating in the clockwise direction by looking at the bright and dim region of the image taken, is it the resolution of ...
0
votes
1answer
19 views

Wheel RPM measuring reference point [closed]

Attached is picture of a car wheel in 3D. Assume it is suspended and rotating in the air. If I put a nut + proximity sensor right on top of the nut within the red line to measure RPM, will the nut ...
2
votes
1answer
61 views

Definition of Vector

In a book on General Relativity that I am reading, it defines a vector as an object or array of numbers that transforms like a vector (under rotations). I understand that under rotation $\theta$, a ...
1
vote
0answers
16 views

How will a rotating, circular, and cylindrical body of a superfluid develop in outer space?

Let's consider a rotating (about its center, in the plane cutting the initial circular and cylindrical form into two halves), circular, and cylindrical body of a superfluid somewhere in outer space. ...
1
vote
5answers
80 views

Effect of earth's rotation in ballistics

For this purpose, let's consider earth's rotations constant. Do earth rotation momentum get transfered to any object (a missile for example) that get's lauched? If so, why do we have to consider earth ...
3
votes
1answer
78 views

Wigner-Eckart theorem: Are expectation values of all vector operators parallel?

The Wigner-Eckart theorem tells us that for any tensor operator, $\mathbf{T}^{(k)}$ that \begin{align} \langle jm|T^{(k)}_q|j'm'\rangle = \langle j'm'kq|jm\rangle \langle j||\mathbf{T}^{(k)}||j'\...
6
votes
3answers
150 views

Why do office chairs rotate when pushed/pulled out?

A common source of frustration when I'm at work is the fact that my rolling office chair's wheels rotate whenever I push it forward or backward from my desk, which can cause it to bump my computer ...
0
votes
0answers
17 views

What happens when an impulse is applied at right angles to one end of a rod (free to move on a frictionless surface)? [duplicate]

What will be the difference if we apply this impulse at the center of the rod? Will the translatory motion be same in both the cases?
0
votes
2answers
160 views

Infinitesimal Rotation under Orthogonal Similarity Transformation

I’m reading charpter 4.8 of Goldstein’s classical mechanics 3rd edition that deals with infinitesimal rotations, and the following is the part I got stuck: (p.166~167) If $d\boldsymbol{\Omega}$ is ...
0
votes
1answer
97 views

Newton's third law for rotating systems [closed]

As often happens for the rotational world, the Newton's law can be restated in terms of angles, moment of inertia and torques replacing displacements, masses and forces (this is one source among ...
0
votes
0answers
21 views

Azimuthal Symmetry is on a certain axes that is not simply the $z$-axes

let's say in a problem, the azimuthal symmetry is along the axis $\frac{1}{\sqrt6}(-1, -1, 2)$. If I create two new basis angles and get solved the LaPlace's equation with that, what should I do to ...
-1
votes
2answers
95 views

How the centripetal forces work on a point in a rigid body? [closed]

I know it was a question but when I asked last time I did not know the answer. It has been suggested that the question is not clear, it's badly written. Now I know the answer and I can introduce them ...