# Questions tagged [rigid-body-dynamics]

The study of the movements of a collection of connected bodies subject to external forces in the absence of deformation. This tag should be used for questions on the analysis of 2D/3D dynamics of rigid bodies, do NOT use this tag because your question contains a rigid structure.

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### Determining the principal moment(s) of inertia and KE of a cuboid

I am a bit perplexed with regards rotations about a certain axis. Say we have a cuboid with lengths $l_1$, $l_2$, $l_3$ (not a cube, so $l_1$ does not equal $l_2$ does not equal $l_3$). I am okay with ...
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### Pitch in Screw Motion of Rigid Body

Does anyone know how to prove these statements?
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### Rigidity Vs. Viscosity and Bulk modulus

Can one consider a rigid body as a fluid having infinite viscosity and bulk modulus? Basically, I am asking if is it possible to start from Navier-Stokes equations (including Bulk modulus and ...
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### Does a rotating rigid ring (or other rotating rigid body) in space generate heat?

I don't have training in physics (so forgive me if I use the wrong terms or mix up concepts), but I was thinking about “artificial gravity” in space. If a spaceship were being propelled by some force, ...
289 views

### Is there a quantum analogue of the “Tennis Racket” theorem?

A non-trivial result from studying the classical mechanics of an extended object shows that rotation about an axis whose moment of inertia is between the largest and smallest moment-of-inertia axes is ...
35 views

### Applying forces to move spaceship without torque

I'm building a game prototype where you control a 2D spaceship by activating it's thrusters. Below is an schema of my thruster. It applies a force in the direction of the arrow, with a variable and ...
63 views

### Why is the vibrational kinetic energy of a body ignored when calculating the total kinetic energy?

In calculating the total kinetic energy of a macroscopic rigid body, we add the total translational kinetic energy and the total rotational kinetic energy of the constituent particles. Why is the ...
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### A problem on Degrees of Freedom

Degrees of freedom of a massless rod, moving freely in space with a speck which is constrained to move on it? It seems massless rod is ideal I am very confused how to regulate degrees of freedom. ...
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### If the net external moment on a body about a point is zero

I was told that If net external moment of some forces is zero about a point, then the net external force passes through the point. I know it's not true in general, what was the special condition ...
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### Relating angular velocity between rotating frames

Notation I'll be using Hubert Hahn's notation for my question. Hahn has an algebraic treatment of all values. $\omega_{GN}^{G}$ is the angular velocity of frame $G$ with respect to frame $N$, ...
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### Energy Conservation in Rolling without Slipping Scenario [closed]

A solid ball with mass $M$ and radius $R$ is placed on a table and given a sharp impulse so that its center of mass initially moves with velocity $v_o$, with no rolling. The ball has a friction ...
24 views

### Physical meaning of product of inertia [duplicate]

I'm trying to intuitively get this concept. Conventionally, $I_{xz}$ for example, signifies the $x$ component of $L$, the angular momentum, when $\omega$, the angular velocity, is in the $z$ direction....
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### Are the ideas of angular velocity, angular acceleration, angular momentum, torque, etc only helpful for rigid bodies?

For rigid bodies, all the particles can have different linear velocities but the same angular velocity, so it makes it convenient to talk about the angular velocity instead. From there, we get to ...
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### Confusion regarding configuration space of a rigid body as described in Theodore Frankel

Assume a rigid body has one point, the origin of $\mathrm{R}^3$, fixed. By comparing a cartesian right-handed system fixed in the body with that of $\mathrm{R}^3$ we see that the configuration of the ...
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### How can all particles of a rigid body have identical angular velocity when their position vector is not perpendicular to the axis?

Consider this spinning disk, in a 3D coordinate system. It is translated above the origin of the coordinate system and spinning around the axis given by this translation vector. Every source I can ...
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### Derivation of $\frac{d}{dt}\mathbf L = I \dot{\boldsymbol \omega} = \mathbf M - \boldsymbol \omega \times \mathbf L$

I would like to know how the above quantity is derived (Here $\mathbf{M}$ is the rate of change of angular momentum with respect to a non inertial frame).I tried looking at various sources and couldn'...
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### Acceleration of a merry-go-around, when a human is walking along it's rim

According to law of conservation of angular momentum, the merry-go-around is expected to rotate at constant angular velocity, while the man walks along it's rim with constant speed relatively to the ...
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### Generalized coordinates of two unequal masses attached to a mass-less rigid rod

Consider a system of two particles of masses $m_1$ and $m_2$ moving in a plane. Let the respective position vectors be $\mathbf{r_1}$ and $\mathbf{r_2}$. The particles are attached at the end of a ...
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### What is the moment acceleration of the center of mass for a rigid body under an external force

As shown in the following, a rigid body experiences an external force $\overrightarrow{F}$ away from its center of mass C: The rigid body is assumed to be free in space, experiencing no other force. ...
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### Can someone please explain Gyroscopic precession?

So I watched this video It is a fairly popular one by veritasium, and one that confused me. I was wondering if someone can cover the physics behind this in a intutitive and easy to understand manner. ...