The time derivative of angular position used when studying rotating objects or systems.

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32 views

tangential acceleration and angular acceleration [on hold]

$$r= 2 \text{ m}$$ $$a_{\text{tangential}}=\frac{\pi}{4} \text{ m/s}^2$$ for half a turn What is the angular velocity from rest of the circular path? $$a_{\text{angular}} = ...
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22 views

Find angular speed? [on hold]

The propeller blades of an airplane are 4.0 m long. The plane is getting ready for takeoff, and the propeller starts turning from rest at a constant angular acceleration. The propeller blades go ...
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1answer
30 views

Calculating estimated HP from velocity, auto weight, and constant acceleration

I am working on a simulation program that runs theoretical performances of different cars and was wondering if there is a way to estimate the HP at any running RPM? the problem is (and this may be me ...
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1answer
114 views

Rolling a ball into a cone; what should the forces overall be?

This is my solution to finding angular displacement/velocity/acceleration on cone so far. Consider a cone, with an apex of half-angle $\psi$ pointing down, and a height of $h$. If I roll a ball into ...
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2answers
6k views

Calculation of the G-force

I have a formula which is $\text{G-force} = \frac{v\omega}{9.8}$, where $v$ is speed and $\omega$ is the angular velocity. I've seen on the internet that G-force is actually $\text{acceleration}/9.8$. ...
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2answers
938 views

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 ...
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36 views

Torque, angular velocity, keeping track of the rotation of a sphere

I'm trying to simulate a rotating sphere due to a torque on a specific point on the sphere. Say the sphere is connected to a string (so variable length) on the bottom, on $(r, \theta, ...
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58 views

A question about a body moving in horizontal circular motion

I have some related questions about a body moving in uniform horizontal circular motion: The body moves with a constant angular velocity on a rough horizontal surface. It is attached to a string that ...
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85 views

How much effort would be required to fix the Earth's rotation?

Given that the earth's rotation has been slowing down by very slight amounts over time, forcing us to introduce leap seconds and so forth into our clocks and calendars, I would like to ask if this ...
8
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1answer
359 views

Is it expected that all stellar black holes will be spinning near the maximum allowed $\omega$-velocity?

Using a bit of classical reasoning I'm imagining black hole formation to be much like an ice skater pulling in her arms: Now, the size difference between a star and its black hole can't even be ...
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1answer
25 views

If a body move around the circle $n$ times then? [closed]

What will be its angular frequency if it rotates $n$ time in one second? I know its a homework type question but I am self studying and cannot have someone solve this problem. Help me please.
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3answers
51 views

How can I measure the speed of a figure skater's spin?

My daughter is a figure skater and needs to measure how fast she is spinning before she loses her position. This is a science project for 7th grade. I have looked for devices to possibly measure her ...
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1answer
69 views

When two objects roll down an incline, does the velocity increase?

I know the basics of rotational motion but this question just confused everything: The answer to the question is A. But why? My problems: If first, I treated both the disks as two particles, ...
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0answers
31 views

What is the relationship between the angular speed and the diameter of the eye of a water vortex?

In a water vortex formed in a plastic bottle, what is the relationship between the angular speed of the water and the diameter of the hole in the cap? I would have expected that according to the ...
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2answers
1k views

What are the expressions for rotational and translational kinetic energies of a system of point particles?

Consider a system of point particles , where the mass of particle $i$ is $\mu_i$ and its position vector is $r_i$. What are the expressions for translational kinetic energy and rotational kinetic ...
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114 views

Time derivative of angular velocity in rotating reference frame

I am going through a section in a textbook regarding the Newton Euler equations for a system of rigid bodies (robotics text). There is a particular line in the derivation I don't understand, I've ...
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1answer
70 views

Angular acceleration and linear acceleration

I have a small confusion. I learned very recently that all particles of a rotating body have the same angular acceleration but different linear acceleration (same for velocity as well). But how is ...
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0answers
24 views

The Linear acceleration in Gyroscope

I am trying to understand theory behind the Gyroscope. I found this article that explains things in much detail. But I am unable to understand how that perpendicular acceleration components (a1, a2) ...
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1answer
97 views

What formula connects the moment of inertia and angular velocity? [duplicate]

I need to determine angular velocity of a disc when a man with given mass and speed whacks on the edge of it. I calculated the total moment of inertia of disc and body, how do I calculate the ...
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60 views

Examples of projection of angular velocity

I am looking for examples where the projection of angular velocity vector onto a different axis, has some interesting physical meaning in day-to-day contexts. For example, if a gramophone turntable ...
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42 views

Angular momentum in an accretion disk

I need to plot the time evolution of the total angular momentum in an accretion disk. This confuses me because I thought this should be constant, since angular momentum has to be conserved? I'm given ...
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1answer
73 views

Why does this model fall apart when angular velocity is small?

I'm doing a physics problem in which a marble spins around a spinning bowl and both have angular velocity $\omega$. It rotates with radius $r$ around the central axis and the hemispherical bowl has ...
2
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2answers
68 views

Having trouble understanding how the centrifugal force works

I thought that I understood the centrifugal force earlier, but I can't seem to grasp how it interacts when considering that everything is relative? Let's imagine that you are the only one in the ...
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2answers
1k views

Proof of centripetal acceleration formula ($a_c = \frac{v^2}{r}$) for non-uniform circular motion

The formula for centripetal (radial) acceleration is well known, and there exist many proofs for it: $$||a_c|| = \frac{||v||^2}{r}$$ However, all the proofs I've seen rely on the fact that it is ...
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2answers
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Angular Velocity expressed via Euler Angles

On the top of the fourth page from here, the author trivially derives the components of angular velocity, expressed via Euler angles of the system. I fail to understand how the components of angular ...
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2answers
199 views

How do you travel in a circular orbit around a massive body?

I am trying to figure out how an object could achieve a perfectly circular orbit. Given a mass for the planet or other body the object is orbiting and a distance from the center of mass, how fast ...
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1answer
66 views

Have I calculated Angular Acceleration correctly?

I am teaching myself basic mechanics from a standing start. I am trying to understand Angular Acceleration and have set myself a problem to solve. My answer 'feels' wrong, so I'd like some help to ...
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1answer
50 views

How do I calculate the necessary velocity of two reels of tape to maintain constant tension on the tape?

I have a real-world problem that I'm quite certain can be solved with a formula. Unfortunately I myself am not particularly skilled in the realm of physics or math. Any and all help is very much ...
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1answer
345 views

Angular velocity $\omega$ by $v$

We have two girls, with mass ($M$). They become close to each other in speed of $V$. The distance between them is $3L$. I was asked to calculate the Angular velocity ($\omega$) of the two girls. So ...
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215 views

Ten-ping bowling: Can a ping pong ball knock over a bowling pin?

In this video we see a rather unorthodox bowling technique on display. The gentleman appears to knock over all of the pins using only a ping pong ball. It's a fake, of course: you could never knock ...
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3answers
80 views

How can I compute the angular velocity of a triangle formed by three particles knowing their instantaneous positions and velocities? [closed]

I have a set of trajectories of three particles and their instantaneous velocities. I would like to compute the 3 components of the angular velocity pseudovector of the fictive triangle formed by ...
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1answer
387 views

Finding stopping time when only given initial angular velocity and an expression for angular acceleration?

Question: A wheel starts is spinning at $27\text{ rad/s}$ but is slowing with an angular acceleration that has a magnitude given by $\alpha(t) = (3.0\;\mathrm{rad/s^4})t^2$. It stops in a time ...
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1answer
54 views

Angular velocity vector in terms of motion of an object

May be it is small question in this forum but I'm trying to get the feel of the understanding about the angular velocity. If this question is getting rejected please kindly refer me to appropriate ...
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1answer
2k views

Difference between angular frequency and angular velocity?

What is the difference between angular frequency and angular velocity? I think one is used for SHM and the other for circular motion? Also can both be used for centreptal accelartion? I think angular ...
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65 views

Are there 'special' cases for when special relativity can be applied for accelerating bodies?

I have the following theoretical situation: A space station modeled as a ring in free space is rotating about its centre point at a high speed. I am trying to work out where time flows slower. From ...
3
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1answer
67 views

Will a rotating body gain linear acceleration in water?

If a ball is floating in water and it has some angular velocity, will it gain some linear acceleration from the drag on it as it rotates? Edit: This is how I pictured it. I guess my reasoning is ...
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2answers
516 views

Relative angular velocity and acceleration

Background: (Irodov 1.55) Two bodies rotate around intersecting perpendicular axes with angular velocities $\hat\omega_1,\hat\omega_2$. Relative to one body, what is the angular-velocity and ...
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Does Earth's Rotation Affect Its Shape?

The question I am working on is, "Consider the following. (a) Find the angular speed of Earth's rotation about its axis. rad/s (b) How does this rotation affect the shape of Earth?" I am fully ...
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99 views

Angular velocity in fluids (Air resistance)

Few days ago I started making physics engine on directx. As it obvious I have encountered one problem. I can't find formula of air resistance for angular velocity. I only able to find drag force, but ...
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1answer
139 views

How do I find angular and linear velocity after normal force and “infinite” friction force?

Look at this picture: http://i.imgur.com/mY8ShkV.png Here we have a ball resting on top of a platform (the contact point is marked red). I know the normal vector (marked green). I also know the mass, ...
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1answer
89 views

Why is it that angular acceleration is constant in different instantaneous reference frames?

Take the following example: A rod (of length L and mass m) is held horizontally at both ends by supports. One is instantaneously removed. The specific problem is to prove that the force on the other ...
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79 views

Rolling in 3D using Torque, Angular Momentum/Velocity

I'm stuggling to get a simulation working correctly. Below you can see what I am attempting to do. You can also view it here. Can you spot where I'm going wrong? (Calculated at start) 1) Inertia ...
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1answer
426 views

How do I convert tangential speed to angular speed in an elliptic orbit?

I am running an animation of a satellite in an elliptic orbit (defined by a parametric equation for $x$ and $y$ as a function of $t$) and want to make sure the spacecraft is traveling at the right ...
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2answers
120 views

Does an object on top of a lever arm have angular velocity at the moment when the lever is released?

Suppose there is a lever arm fixed at one end, and it is parallel to the ground. There is an object resting somewhere on top of the lever arm (the object is not attached to the lever). At the moment ...
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1answer
83 views

Stability of square of masses on strings under rotation

Imagine we have a square of masses, $m$, connected by light inextensible strings, length $l$, rotating around it's centre at angular speed, $\omega$. It's easy enough to show that there must be a ...
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1answer
215 views

Why is body frame angular velocity nonzero?

This question is relevant to Euler's angles and Euler's equations for a rigid body. Why aren't $\omega_1$, $\omega_2$ and $\omega_3 = 0$ in the body frame? How can we measure $\vec\omega$?
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1answer
132 views

Paradox of angular velocity

For a torque-free symmetric top, the Inertia tensor has an inverse $I^{-1}$, and $L=I\omega$. Which implies that $\omega=I^{-1}L$. But since $I, L$ are constants, $\vec\omega$ is a constant. However, ...
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1answer
515 views

Rod slipping against block due to gravity? [closed]

A uniform rod of mass $m$ and length $l$ is pivoted at point O. The rod is initially in vertical position and touching a block of mass M which is at rest on a horizontal surface. The rod is given a ...
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1answer
144 views

Does angular momentum conservation imply that angular momentum $J$ is parallel to angular velocity $\omega$?

In other words, does $\frac{dJ}{dt} =0$ imply $J \times \omega =0$? Counterexamples or proofs would be helpful! EDIT: This question originally asked if $\frac{dJ}{dt} =0 \Leftrightarrow J \times ...
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12k views

What is the difference between angular speed and tangential speed in a circular motion?

I was looking a long time for the way the equations of this two speeds are obtained, and i found pretty much nothing important, so can someone explain how are those obtained, and which is the ...