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Questions tagged [rotation]

Circular motion about a central point or axis

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48 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 ...
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0answers
10 views

Rotational friction coefficient

How to find the rotational friction coefficient? Can it be found using the same procedure used to find the static friction coefficient?
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23 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 ...
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2answers
27 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 $\...
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0answers
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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 ...
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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 ...
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3answers
89 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. ...
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1answer
35 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 ...
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1answer
42 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, ...
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0answers
16 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 ...
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3answers
129 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 ...
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2answers
165 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 ...
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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 ...
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1answer
52 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 ...
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0answers
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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. ...
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5answers
72 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 ...
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1answer
57 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'\...
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3answers
101 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 ...
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0answers
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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?
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2answers
150 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 ...
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1answer
74 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 ...
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0answers
18 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 ...
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5answers
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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 ...
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0answers
19 views

Why sand in a water collects at center on rotating the water? [duplicate]

We commonly observe that on rotating dirty water, the dirt in water collects at the center. But why does it happens, and why does it not collect at edges due to centrifugal force. Does something ...
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0answers
22 views

How do the principles of weather vane design change for underwater applications?

I am doing some research into the use of weather vanes under water. This "water vane" would serve the same function as a weather vane does in air, just while submerged in water. I understand that ...
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0answers
32 views

Forces on a Rotating Rigid Body

This question has been puzzling me for some days now and I thought I might ask you guys for some help. Say that we have a rigid body (like a rod) that is in a vacuum in space. Furthermore, say that ...
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1answer
168 views

Difference between torque, moment and couple

I know the basics of them like Torque is force multiplied by the distance (from the point where there is no rotation like centre of gravity). Couple acts because of two equal and opposite forces ...
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1answer
102 views

Classical angular momentum components are numbers. Can they be generators of some symmetry group?

In Quantum Mechanics (QM), angular momentum turn out to be the generator of rotational symmetry. This is trivial to see because in QM, angular momenta are defined by the commutation relations $$[J_j,...
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1answer
73 views

Relation Between Cross Product and Infinitesimal Rotations, Generators, Etc [duplicate]

Looking into the infinitesimal view of rotations from Lie, I noticed that the vector cross product can be written in terms of the generators of the rotation group $SO(3)$. For example: $$\vec{\mathbf{...
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2answers
115 views

Angular Momentum in a Straight Line

Edit: This is not a duplicate question. The other question asked how angular momentum remained constant if the distance varied. This question asks why you can select any point and calculate angular ...
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3answers
241 views

How to distinguish between angular frequency $\omega$ and frequency $f$

The relation between the "regular" frequency $f$ and the angular frequency $\omega$ ($\omega = 2\pi f$) is clear to me. However, every time I see "rotations per second" I really get confused as to ...
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2answers
71 views

Gravitational potential energy of a rod, attached by its end to an axis

Situation: We suppose a rod is attached by its end to some pivot, and is allowed to fall from a horizontal position. As this occurs, the rod loses gravitational potential energy ($∆U_G$), say 10J, ...
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2answers
183 views

Torque, Angular Acceleration and Linear Acceleration

We know that we torque is applied, it cause an angular acceleration in the rotating body similar to what a force does to a body moving on a straight line. But my question is, Does Torque affect the ...
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0answers
29 views

Lense-Thirring effect: Revolution, precession, rotation … inside rotating shell?

This is a very basic and vague question (I don't know general relativity, nor much physics, but am interested in this question for idiosyncratic reasons). Consider a rotating spherical shell of mass ...
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3answers
95 views

Maxwell's Equations in a Rotating Frame of Reference: How to transform E and B Fields?

I know there is allready a question on the topic, here, however the answer to this question deals with GRT, and I want to keep the level of the question basic (however enough to deal with thing like "...
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1answer
227 views

The physics of a cornering wheel and the centripetal force

Can a rolling wheel create a side force without first rotating on a vertical axis? There is something wrong with the way we describe how a cornering vehicle wheel creates a cornering force. I think ...
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0answers
32 views

Windowless space station: rotation vs. gravity ring vs. frame dragging?

Imagine a windowless hollow cylinder, with an observer sitting inside on the curved wall. Something is pulling the observer against that wall. The observer can also walk easily along the inner ...
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2answers
53 views

Is the acceleration of a rotating body always it's centripetal component? [closed]

For constant circular motion where a rotating mass accelerates angularly. Would the linear acceleration of the rotating mass always be equal to its centripetal acceleration e.g. The earth's ...
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1answer
34 views

How can I find the power given only the torque?

I have a system where I am trying to find the power generated by a DC electric generator. However, I am not very familiar with generators, so I am having difficulty determining the rotational velocity....
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1answer
43 views

Why should the friction between two disks be zero when there velocity is same? [duplicate]

In this video here, Walter Lewin mentions two discs of different radius $r_1$ and $r_2$, of the same density, where the first disk is initially rotating, while the second is at rest. In the videos ...
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1answer
34 views

Should there be a significant differential in wind velocity indoors vs outdoors in relation to Earth's rotating atmosphere?

What is the behavior of a rotating Earth's atmosphere indoors? Should there be any differences experienced between the atmosphere spinning in lockstep with the Earth outdoors vs. closed-off indoors? ...
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1answer
41 views

If a ball were to roll through a loop, would the normal force change when compared to a frictionless block?

I am currently working through the following problem: Reaching part c), we are required to repeat the former parts using a spherical mass instead of a frictionless cube. I have no problems with the ...
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2answers
59 views

Rotation of a Bicycle Wheel

Circular motion at a constant velocity requires a net force toward the center of rotation. If I stand a bicycle on its seat, wheels upwards and spin the wheels with my hands, they start rotating. ...
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1answer
111 views

How to obtain $Y$ rotation with only $X$ and $Z$ rotation gates on the Bloch sphere?

Let's say you have a system with which you can perform arbitrary rotations around the $X$ and $Z$ axis. How would you then be able to use these rotations to obtain an arbitrary rotation around the $Y$ ...
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2answers
217 views

Rolling objects released from rest: time down the ramp [closed]

Since we are given the values of I for each object, I was able to calculate the KE's of each: the solid spheres had KE of $1/5mv^2$; the hollow sphere had a KE of $1/5 mv^2$, and the hoop had $1/2mv^2$...
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0answers
65 views

What does a basis rotation correspond to physically for linear position-momemtum?

For polarization and angular momentum, rotating the basis corresponds to a very straightforward physical transformation, namely, the physical rotation of an experimental apparatus about an axis in ...
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1answer
116 views

Relation between Spin 1 representation and angular momentum and $SO(3)$

This is a naive question. It occurred to me while studying in detail the the Spin 1 angular momentum matrices. The generators of $SO(3)$ are $J_x= \begin{pmatrix} 0&0&0 \\ 0&0&-1 \\ ...
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2answers
179 views

Rolling Without Slipping and Rotational Energy

I'm a little confused. Translational energy and rotational energy add separately, according to my textbook, to give the total kinetic energy of a moving object. That means that for a disk ...
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1answer
233 views

Integrating over Euler Angles

I have a $6\times6$ matrix having its elements being functions of Euler's angles (ZXZ rotation scheme) representing a tensor physical property. To find the average of the tensor property, I need to ...
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2answers
85 views

Rigid bar on a pivot

Say we have a solid bar in space. It is on a pivot, the pivot being right at the bar's center of mass There is a massless rocket pushing on one end of it, making it spin, faster and faster. Suddenly,...