Circular motion about a central point or axis

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24 views

Effect of atmospheric drag on earth's rotation

Okay, so I had a question answered regarding the earth rotating and planes flying east and west but one part of the answer talked about how the atmosphere is moving along with the earth (same angular ...
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3answers
65 views

Air flight and Earth's rotation

I read a response asking why flights of equal distance east and west take roughly the same time (disregarding wind actions). I have trouble visualizing part of the answer; "the speed of the rotation ...
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0answers
26 views

Is there a physical formula or equation to describe change in size of rotating tire?

I've heard that tires will actually grow larger when you are moving, and shrink back down when you stop. I was wondering if there is a way to calculate the size of a given tire, and what the variables ...
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0answers
21 views

What is the exact physics behind the heading indicator?

If I know right, the really basics of its functioning is that a quickly rotating gyroscope's axis of rotation moves into the north-south direction, due to the torque resulting from the tangential ...
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1answer
207 views

To prove uniqueness of the rotation tensor associated with rotation of a rigid body

Suppose there are $N$ particles embedded in a rigid body which undergoes some random rotation such that: $$ \overline{\overline {R}}_{ij} \otimes \vec{a}_{ij} = \vec{b}_{ij}$$ where, $i$ and $j$...
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1answer
513 views

Angular velocity relative to different frames

In Goldstein it is said "It is intuitively obvious that the rotation angle of a rigid body displacement, as also the instantaneous angular velocity vector, is independent of the choice of origin of ...
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9answers
7k views

What is the difference between translation and rotation?

What is the difference between translation and rotation ? If this were a mathematics site, the question would be at best naive. But this is physics site, and the question must be interpreted as a ...
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2answers
38 views

Derivation of Specific Rotation formula?

This is sort of a weird question, so bear with me: I was reading about how chiral molecules rotate plane polarized light and decided to think of a "logical" formula for expressing the amount that ...
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2answers
208 views

Rigid Body Dynamics - Calculating Rotation of an Object

I've looked everywhere and I can't quite find a concise answer, especially due to my limited knowledge and understanding of terminology. I found something called Rodrigues' Rotation Formula that ...
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2answers
247 views

Need help understanding angular acceleration due to gravity

The question asks what the angular acceleration of an uniform disc of radius $R$ rotating about an axis passing through its edge if it is released from rest with its center of mass at the same height ...
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2answers
50 views

Why anticlockwise movement is present in the whole universe [closed]

Why electronic movement in its orbit and planet orbital movement along with milky ways have anticlockwise movement. is there any specific reason. The Sun is rotating anticlockwise from its axis as ...
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0answers
36 views

Dampening a swinging mass

Suppose a bar (black) sitting on a suspended ball (blue) has two rigid loads attached to it (red, green): Because the bar sits on a ball, the bar can swing clockwise or anti-clockwise. Suppose the ...
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1answer
185 views

Rotation motion like the number 8

I'm a college student majoring in culinology and I'm trying to find out the reason or method of the number 8 motion. Responses doesn't have to be in culinology examples, but that would be a great help ...
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3answers
52 views

Force at axis of spinning wheel

This is a newbie question, but I don't quite understand the forces at work when an object is rotating. So I've read that i can use my right hand to determine the direction of the force at the axis ...
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1answer
198 views

How can angular velocity be constant even when there is a torque by friction?

A cylinder at rest lying on a rough ground is given an impulse which imparts a translational velocity (no angular velocity) to it. The question goes ahead with finding time after which rolling starts ...
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1answer
57 views

Vertical circular motion(with gravity)

Let's say I have a stone tied to a string and swing it vertically upwards. Now, if I provide an initial velocity such that the velocity of the stone = 0 at an angle greater than 0 from the horizontal(...
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2answers
44 views

Rotation matrix for aligning x-axis in an arbitrary direction

I want to align the x-axis of my coordinate system, with an arbitrary direction in space $\hat{n}$. About which axis should I rotate? Ceratinty rotation about x-axis or $\hat{n}$-axis will not serve ...
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0answers
31 views

A point on a disc travelling at the speed of light [duplicate]

This might be a duplicate of this. I had an interesting thought experiment: suppose that you have a disc of a 1 m radius, where a point P2 inside the disc travels at the speed of light. You have a ...
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0answers
7 views

Pointer to reference for rotational dynamics for large torques?

It's my understanding that when dealing with rotational dynamics (e.g., a gyroscope like at time=2155 seconds of https://youtu.be/N92FYHHT1qM?t=2155) that the equation for relating the speed of ...
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0answers
48 views

Why does a fan blade appear to spin backwards when spun really fast?

This a phenomenon which I notice everyday but never really took an interest in. Why does a fan (or any other rotary object), when spinning really fast, 'appear' to slow down, upto a certain rpm, then ...
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2answers
100 views

Pauli Matrices & 2D Rotation Operators?

I was doing a strange calculation with my teacher the other day: find the eigenvalues and eigenvectors of the 2D rotation operator. Intuitively, there should be no solution to this problem in $\mathbb{...
5
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2answers
466 views

How is Chasles' Theorem, that any rigid displacement can be produced by translating along a line and then rotating about the same line, true?

Chasles' Theorem in its strong form says: The most general rigid body displacement can be produced by a translation along a line (called its screw axis) followed (or preceded) by a rotation about ...
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4answers
146 views

Rotation of a vector

Is a vector necessarily changed when it is rotated through an angle? I think a vector always gets changed because its projection will change, and also its inclination with axes will always change. ...
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0answers
37 views

Are there characteristics that distinguish our universe?

Are there any defining characteristics of our universe that could be different for other universes (or "instances of our universe") that operate under the same laws of physics? And which, if any, are ...
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0answers
30 views

Rotation operation on spin-1/2 particles

How does rotation operators work on a particle? What does it do on the particle conceptually? Also does particles spin on its axis?
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3answers
44 views

Why does a pot start rotating when coffee is stirred inside?

I usually make Turkish coffee as my morning coffee. I have a small somewhat rounded pot with handle on one side. I noticed that when I pour water in and start stirring, pot has a tendency to start ...
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3answers
52 views

Axis of rotation and rotating rigid body [closed]

We know that angular momentum of a solid disk rotating with angular velocity $\omega$ is given by $I\omega$ about its center. Now if I chose any axis (parallel to above), will it have same magnitude ...
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3answers
84 views

Rolling dynamics of round objects down an incline

If a cylinder is rolling down an inclined plane with inclination $\theta=30^\circ$ (with coefficient of static friction between cylinder and the plane $\mu_s=0.8$) without slipping and it has mass $...
4
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1answer
193 views

What are phase conventions in angular momentum and rotation calculations?

I work with complicated angular momentum calculations related to atomic physics; nevertheless, I never need to use anything related to a phase convention (apparently because it's taken care of in a ...
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3answers
76 views

Direction of deflection of Coriolis force on Earth

I'm a bit confused about Coriolis force direction on Earth. The observed deflection is to the right in the northern emisphere and to the left in the southern one. But what about an observer in the ...
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2answers
30 views

How to calculate the acceleration, if the mass-center is not on the force-vector's line (2D)

In a 2D plane there is an object, whose center of mass is at the $P$ point. The mass of the object is $m$. We apply a force $\vec F$ at the point $A$. If the center of mass is on the line, defined ...
4
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0answers
39 views

Why rotating reference frames are not inertial? [duplicate]

Let's say I'm standing on the equator, and that there is no other reference point in the sky. If the planet is rotating, then I measure my weight to be lower than if it is not. But given that I have ...
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5answers
107 views

Rolling without slipping taking the contact point as pivot

I'm confused about this "rolling without slipping" kind of situation. Or better in this case the object is rolling and slipping, just use the label "rolling without slipping" to identify the kind of ...
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1answer
18 views

Moment of Inertia for objects moving in a circle?

I have been treating objects moving in a circle as a hoop, where $I=MR^2$ and it's been working but I feel like it works for a different reason from what I'm thinking. How do you actually find the ...
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1answer
27 views

For a rolling object, is the tangential velocity the same as the velocity of the center of mass?

For example, a solid disk rolling down a hill would include both rotational and linear kinetic energy. For the rotational kinetic energy ($\frac{1}{2}I\omega^2$) the angular velocity becomes $v/r$ but ...
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2answers
36 views

Why does the angular speed formula end up in radians per second?

So, in my homework I am given the radius and also the tangential speed $v$, the measurement for radius is meters; the measurement for $v$ is $m/s$. I don't understand how by after calculating the RPM ...
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3answers
65 views

Rotation of rigid body with two different angular velocities

Consider a cylinder that rotates about a vertical fixed axis with angular velocity $\vec{\Omega}$ while rotating about a vertical axis passing through its center of mass with angular velocity $\vec{\...
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1answer
38 views

If a rotating ball gets disintegrated to dust or energy what happens to its angular momentum?

Say a rotating ball or neutron star gets completely annhilated to energy by meeting its anti-matter counterpart (also rotating in the same direction), what happens to the angular momentum? It cannot ...
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1answer
38 views

Coriolis object deflection and conservation of angular momenutum

I'm trying to understan kinematic inertial explanation of the apparent deviation of objects due to fictitious forces in rotating Earth. Take an object moving from the equator northwards, or ...
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1answer
44 views

Tension as a function of distance from the centre of a rod AB rotating about its end A [duplicate]

My confusion is- 1) While taking limits, tension at end B of rod is taken 0, The function comes showing maximum Tension at end A. But it seems to me that that at end A, T must be 0 as x=0 and at end ...
0
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1answer
26 views

Derivative of angular momentum of rigid body

I found this equation that describes the change in angular momentum $\vec{L}$ of a rigid body rotating about a fixed point $O$. $I_o$ is the moment of inertia of the body with respect to the axis of ...
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1answer
19 views

Angular velocity and velocity of CM indipendence in rigid body motion

In the most general case, in rigid body motion the linear velocity of the center of mass $v_{cm}$ and the angular velocity of the rigid body $\Omega$ are not related with each other. Which condition ...
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3answers
83 views

Rolling without slipping in absence of friction force

I'm confused about a rolling without slipping situation. Suppose to have a disk of radius $R$ on a floor, and exert a horizontal force at a certain distance $r$ from the center of mass. I would like ...
0
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1answer
21 views

Calculation of support reaction in rigid body rotation and collisions

I can't understand the logic behind the calculation of torques exerted by supports in rigid body motion, especially rotation. The equation of angular momentum is $$\vec{\tau}=\frac{d\vec{L}}{dt}\tag{...
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1answer
39 views

How to simulate an accelerometer in code

I want to write a simulation of an accelerometer (with a fixed X and Y axis in this case but with respect to a world coordinate frame) on a stick, rotating in a circle around a fixed point. From that ...
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1answer
36 views

Could gyroscopes be use to control orientation of satellite?

In the game space engineers, the player can control the angular movements of a spacecraft with gyroscopes. Just to be clear, the purpose of this gyroscope is not to measure rotation, but to actually ...
2
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1answer
51 views

Contraction of a rotating system

Consider a system of two masses that rotates with constant angular velocity. When a force contracts the system the velocitie of the two masses increase. I understand this in terms of conservation of ...
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1answer
32 views

Instantaneous axis of rotation of a rigid body

For the description of rigid body motion, any point $O$ of the rigid body could be taken as reference, since the velocity of a generic point $P$ can be written in function of the angular velocity $\...
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1answer
68 views

Calculate the distance from the axis beyond which the particles have slid off a rotating disk

A collection of small particles is distributed on the top surface of a disc that is rotating at 91 revolutions per second, about an axis, which is vertical. Some of the particles slide off, and some ...