Questions tagged [rotational-dynamics]

A tag for questions about the mechanical interactions of rotating objects, including torque and angular momentum.

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Trouble implementing transfer function of a wheel driving force observer

I'm trying to implement a piece of software that can determine Fd(the driving force of a wheel, shown in figure below) given w(angular vel), Tm(wheel torque) and r(wheel radius). What I don't ...
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Will a rotating disk contraction emit light?

The Ehrenfest paradox suggests an object will become smaller at the outer rim due to contraction, When near light speed. Or actually, any object near light speed will contact and appear smaller in its ...
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Lagrangian mechanics a cylinder on a cylinder barrel

This is a typical problem to be solved using the Lagrangian mechanics, but I have a problem in understanding the rotational energy. The task is to formulate the Lagrangian equation for the system of ...
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Interesting classical mechanics question! Any ideas? Yo-yo in space [on hold]

Imagine a cord wrapped around a wheel in free space (essentially a Yo-Yo). In a frame that is moving with the wheel, what happens to the cord and the wheel when the cord is pulled from 0 velocity to (...
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Tangential velocity after ball strikes wall

I have to solve a problem where there is a ball that goes in the perpendicular direction towards a wall. It strikes the wall and goes back at the same angle it came from. (All the movement are ...
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Angular momentum and torque in gyroscope

In my textbook (Kleppner), the principle of a gyrocompass is given to be "A ﬂywheel free to rotate about two perpendicular axes tends to orient its spin axis parallel to the axis of rotation of the ...
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What is the moment of inertia for two identical masses that lies not symmetrical to each other INSIDE a cylinder? [on hold]

Suppose I have a cylinder with r = 5.2cm, two masses are both ~200g, radius of the mass is 2cm each. If both of them are on the same line as the diameter of the cylinder (mass 1, center of cylinder ...
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Derivation of the time-derivative in a rotating frame of refrence

I have so trouble following Goldsteins derivation of the time derivative in the rotating refrence frame, and its use to derive the coriolis force (sec. 4.9-10) Given an intertial frame of refrence, $S$...
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Principal axes of cube at one of it's corner [on hold]

Find the equation of momental ellipsoid at the corner of a cube of side $2a$ referred to its principal axes. I have specific doubts in this question. At any point, angle which the principal axes ...
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Whats wrong in the torque method to get the time period for a semi cylindrical shell? [on hold]

Problem is : My all working is shown here : using 1 and 2 i am getting it to be 2pi√2R/g using energy equation it will lead us to correct answer but why the torque method is not working? Here A is ...
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Time taken by a round object inside rotating cylinder to exit from a hole

I want to know the time taken by a round object of sphericity of 0.85 inside a rotating cylinder to exit from a hole. The below figure will explain my query in a simple way. The notable points are: 1. ...
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Magnus Effect influencing Hurricane Balls motion?

In the motion of a hurricane ball, two sphere are glued or welded to each other and can be spun at very high RPM's, while one ball is rotating on a surface, the other ball is inclined to the surface ...
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Degree of freedom in ideal and real case

what will be the degree of freedom of a massless rod, moving freely in space with a particle which is constrained to move on it? What is meaning of massless rod?
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Rotating rope with a ring

I have this ideal system. There is a bar with negligible mass and a ring(a point) with mass $m$. Bar is rotating with angular speed $\omega$. If I see that system from Non-inertial reference system I ...
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Why do tensions cancel out in some places but not others?

I was answering a question regarding two rotating particles $P$ and $Q$ with $P$ attached to a fixed point $O$ by a light inextensible string and $Q$ attached to $P$ by a light inextensible string ...
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Why people feel outward force in rotor ride?

I know centrifugal is fictious force but what is possible reason for the force that people feel in rotor ride outwards. The reason for people not falling down is friction force which is in vertical ...
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Equilibrium of a rotating particle

Consider a point like particle rotating in a circle with constant angular velocity. Then there must be a centripetal force ok, now the question is can we say that object in equiliibrium? If your ...
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How can I calculate the internal angular acceleration? [closed]

This is a very well known topic and affects angular velocity. How does changing the moment of inertia affect angular velocity? An object that changes the moment of inertia simultaneously changes the ...
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Hollow cylinder with ball inside rolls down frictionless inclined plane [closed]

I have an question about rotational motion of the following system There is a hollow symmetric cylinder on a friction-less inclined plane (mass M, moment of inertia I, radius R, incline angle a). We ...
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Will the rods rotate about the hinge after collision?

The problem is like this: two blocks(considered to be point masses) of masses $m$ are simultaneously moving with uniform velocities $v_0$ towards the rods and they hit the edges of rod and stick to it(...
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What makes a forever spin top special?

What is the difference between a regular spin top and a forever spin top (which spins for far longer than a regular spin top).? The forever spin top is made out of stainless steel. I would like an ...
I can't find the math of that. Imagine a vibrating object, like a circular membrane, with vibration modes $\phi_{ij}(x,y)$. Let's express the initial vibration state like \$u(x,y,t)=\sum_{ij}a_{ij}e^...