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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Rigid body motion (RBM) transformation of interface points between a rigid and an elastic bodies

Above are pictures of a problem in mechanics. An elastic body occupying domain $\Omega$ is supported below with a fixed support and from above with a rigid body. The following calculations aim to ...
user134613's user avatar
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Direction of static friction in wheel [closed]

If a wheel is rolling right, that means the static friction on the stationary point that touch the ground is pointing left. That creates the torque that moves the wheel right. But if that stationary ...
Dor's user avatar
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4 answers
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How to tell if a force on a rigid body does any work?

In problems in Newtonian mechanics I often need to understand whether there is energy conservation. When only conservative forces (such as gravity) are present, it's obvious. But what about when we ...
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5 answers
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Why can't rotations in general be associated with vectors?

In my textbook, there's a question: A vector has both magnitude and direction. Does it mean that anything that has magnitude and direction is necessarily a vector? The rotation of a body can be ...
archthegreat's user avatar
2 votes
2 answers
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Physical pendulum: axis of rotation

Why is the angular momentum always considered to be parallel to the angular velocity in physical pendulum problems, as if the axis of rotation were a principal axis always? I don't see the ...
lgotta's user avatar
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Why when spinning over non-principal axis, it will change the axis of rotation?

Let's look at a disk which is rotating around non-principal axis. I know the explanation when looking in a rotating frame, the centrifugal force on the edges of a the disk create a torque that wants ...
Dor's user avatar
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How to determine the torque required to decelerate a rotating arm?

I am working in CAD on a robotic arm and wondering what is the appropriate way to determine Torque required from my actuator to decelerate the arm moving at some speed. Below I included a quick sketch ...
SoloLeveling's user avatar
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2 answers
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Angular momentum about an axis other than axis of rotation [closed]

I know the formula for angular momentum about the axis of rotation i.e, $L = I\omega$. But what if I need to calculate the angular momentum about some axis other than the axis of rotation. Is it going ...
yyzr's user avatar
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Rotational work by a force

If we have an object which is acted upon by a force which which produces both translational and rotational motion of body then would the total work done by the force be the sum of its translational ...
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3 votes
1 answer
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Doubt in rotational work-energy theorem

This is a question on work-energy theorem in rotational motion with its answer for the first part of the question. Here, I have a doubt about why is the book taking the translational work done by the ...
yyzr's user avatar
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Combined KE for an object rotating about a point other than COM

I know the KE equation for combined translational and rotational motion, which is $K=Mv^2/2+I\omega^2/2$, and here $v$ is the velocity of COM and $I$ is the moment of inertia about the COM. But what ...
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If a 100,000 ton container ship slams into a bridge at 8.6 knots how much energy was moved into the pylon and at what rate of transfer speed? [closed]

Edit: the entire question is in the title, the answer should be an amount of energy and a value of energy transfer in some unit, but not knowing enough about physics I don’t know what the appropriate ...
MetaGuru's user avatar
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3 answers
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How does rolling without slipping happen physically?

In physics textbooks, problems about rolling usually include the assumption that the rolling is without slipping, meaning that $v=R\omega$ throughout the motion, where $v$ is the translational ...
35T41's user avatar
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5 answers
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Total kinetic energy confusion

This might be a stupid question or has already been asked before, so please refer me to the answer if it has. Let's say we have a rolling ball, which is purely rolling, and there is no friction. (Is ...
Beast's user avatar
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About Constrained Speeds

My question is whether there is any known method, which doesn't use calculus, to find the speed of ball C, given that the speeds of balls A and B are given at a certain moment in time. Suppose that in ...
R. Ferreira's user avatar
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Question regarding dynamic modeling of cable driven robot

I am studying rigid body dynamics and am currently exploring the paper "Analytic determination of wrench closure workspace of spatial cable driven parallel mechanisms". In the paper, the ...
robot_robot's user avatar
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Two bodies rotation separation

I am currently working on programing a small simulation involving two bodies, yet I find myself somewhat unconvinced by the results I'm obtaining. Consider this particular test scenario: I have two ...
Arn30's user avatar
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2 answers
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Proof of Newton's second law of rotation for rigid body

I'm reading over my lectures notes on rigid body dynamics and I'm trying to prove as many results as possible. However I can't seem to prove that $\tau = \frac{dL}{dt}$ for a rigid body, where $\tau = ...
Charlélie Carer's user avatar
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0 answers
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EMF generation by rotating rod without magnetic field [closed]

what is the EMF generated by a conducting rotating rod of mass $m$ and length $l$ in free space without magnetic field. the rod is roating with angular speed $w$? also find the current if the rod has ...
Konakalla Prajith reddy's user avatar
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2 answers
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Forever Pure Rolling? [duplicate]

If a spherical body is given some velocity and it then starts pure rolling on a plane surface(not inclined), will the body come to rest if we ignore other factors like surface irregularities and air ...
Shubham Kumar's user avatar
2 votes
1 answer
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Conservation of angular momentum and the choice of the axis

The problem A ball with radius $R$ slips on a surface with speed $v_{cm}=v_0$, so that the velocity of the center of mass, decreases and the angular velocity $\omega$ increases. The ball starts a pure ...
semola's user avatar
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How does conservation of angular momentum work when a body is rotating on multiple axes? [duplicate]

I'm trying to understand how momentum is conserved when gymnasts twist mid-air while they are doing a flip. In this post, I will refer to the movement of his feet over his head as "rotation",...
Luther Grusovin's user avatar
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1 answer
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What is the formula for how a force affects linear motion on a rigid body?

Say a body (two glued spheres will do) hits a ceiling, and the balls and ceiling are the only things in the universe. I translate the point of impact to the center of mass, calculate my lever arms, ...
Jorge Al Najjar's user avatar
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What is the value of twists vs homogenous transformations?

When reading engineering books they sometimes use twists vs standard homogenous coordinates or quaternions. What value is there in using twists?
FourierFlux's user avatar
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1 answer
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Equivalent Characterizations of Rigid Bodies & Angular Velocity Interpretation

In rotational kinematics, there seem to be two common characterizations of a rigid body: A rigid body is any collection of particles with position vectors $\textbf x_1,\textbf x_2,...$ such that the ...
William Deng's user avatar
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1 answer
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Free Body Diagram of Precessing Top

Consider a heavy, symmetric top spinning on a table, initially inclined at some angle from the vertical. Assuming this angle is fixed, it follows that the weight $\textbf W$ and normal force $\textbf ...
William Deng's user avatar
4 votes
3 answers
503 views

When the gyro moves down, does it spin faster?

First, I have a gyro, $\omega$ is its angular velocity Then, I simple it to When it moves down, there is Gravity does work differently for A and B. Therefore, the angular velocity should be ...
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Kinetic energy of rigid body with unknown center of mass

There is a rigid body undergoing general planar motion (translation+rotation) in 2D. I dont know the translational velocity and center of mass(CM), all I know is the velocity at geometric center (...
Isa Mammadli's user avatar
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Simulating joints in rigid body physics

When simulating rigid body physics with joints(say unconstrained for simplicity) you normally have a constraint force binding the two objects together applied at the point of the joint. This results ...
FourierFlux's user avatar
4 votes
2 answers
787 views

Like force, does the rotational effect of force/torque require some finite time to travel through a real body?

Let's say I am using a long wrench to unscrew a tight bolt because the formulas developed in rigid body statics states that the moment arm should be longer for minimal force application. But how long ...
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Is the equation for degrees of freedom $f=3N-k$ valid for all cases?

Consider the example of a linear triatomic molecule. Now at low temperatures, where we can exclude vibration, quite clearly degrees of freedom, $f=5$, with 3 translational and 2 rotational degrees of ...
Srijan Das's user avatar
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Clarification on order of transformations

Suppose I have two rigid bodies, B1 and B2, I have the position of B2 relative to B1 as a standard homogenous transformation T_12 Similarly I the transformation of B1 relative to the origin as T_01. ...
FourierFlux's user avatar
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88 views

Is there a way to explain torque and Euler's Laws of Motion from Newton's Laws

If I have a rigid rod and I apply a force $\vec F$ distance $r$ away from the centre of mass the torque on the rod is $\vec r \times \vec F$ from the centre of mass and the torque causes the rod to ...
244529's user avatar
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1 answer
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The horizontal components of velocities of two points in a rigid body must be equal but can we conclude that vertical velocities have to be equal?

Consider two points in a rigid body and their velocities at a particular angle to the horizontal. The horizontal components of velocities must be equal so as to satisfy the basic definition of a rigid ...
Anvi Mahajan's user avatar
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Integrating Kinematic equatioms with variable initial conditions

Suppose you have have acceleration and angular velocity for a rigid object but unknown initial orientation, velocity and position. Can you integrate the known data in such a way that it's easy to ...
FourierFlux's user avatar
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1 answer
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Moment of Inertia of a gyroscope

I saw that the moment of inertia could be calculated for bodies as the addition of the sum of their parts, so I was wondering if it could be calculated for the gyroscope that is pictured below I was ...
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16 votes
3 answers
4k views

Spinning gyroscope loses weight?

I ran two tests with a toy gyroscope spinning on a weighing scale that is accurate to $1$mg. The scale was reset to zero before the tests. The gyroscope was flipped over between test $1$ and test $2$. ...
John Eastmond's user avatar
1 vote
1 answer
99 views

Spivak, Classical Mechanics: rolling disc

In page 231 of his brilliant classical mechanics book ("Physics for Mathematicians 1"), Spivak considers the setting where we have a disc rolling on a planar floor such that the plane of the ...
Plemath's user avatar
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1 vote
2 answers
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Mathematical Proof of consistency of centre of mass in a Rigid body

I read that the center of mass remains unchanged in its position with respect to other points in the rigid body, even when any external force is applied to the body. However, I am willing to know if ...
Mathologist's user avatar
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IMU frame to body frame

I am thinking about this problem: My IMU is centered at point O, and my structural body is centered at point p. Points O and P are two points on a rigid body. Point P is always moving and its motion/...
Nick X Tsui's user avatar
1 vote
2 answers
192 views

Calculate rotation from net torque and inertia matrix

I am trying to grasp the concepts of forces applied to a rigid body resulting in a net change of the rotation of the object. This is not a home assignment and I read some resources on both the web and ...
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1 answer
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Modelling the quintuple cork on snowboarding with Euler's rigid body equations

I'm currently brainstorming for my Math AA HL Internal Assessment (a kind of math investigation paper you must elaborate for the IB Diploma) and I've hit a bit of a roadblock. Snowboarding is a hobby ...
Miles Jarra Gloekler's user avatar
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1 answer
78 views

Energy involved in rolling with slipping

A ball rolls without slipping on a table. It rolls onto a piece of paper. You slide the paper around in an arbitrary (horizontal) manner. (It’s fine if there are abrupt, jerky motions, so that the ...
Cognoscenti's user avatar
1 vote
1 answer
65 views

How does friction applied to a rolling sphere in 3 dimensional space

I am doing a rigid body physics simulation program. This simple program can simulate the behaviour of a rigid sphere rolling/sliding on some surface. I need help with computing the friction force on ...
YX L's user avatar
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1 vote
2 answers
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Conservation of Angular momentum for an irregular body rotating about three axes

I am having trouble understanding how conservation of momentum can be used to calculate final angular velocity for a body rotating in multiple axis with an asymmetrical MoI. Suppose a satellite is ...
Katelyn Ball's user avatar
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Two speeds of precession without nutation

I understand mathematically that when you look for solutions to the equations of motion of a spinning symmetric top with a constant inclination angle $\theta$, you get a quadratic equation with two ...
PatrickComposerPhysicist's user avatar
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1 answer
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Doubts about the parallel-axis theorem

I was studying about the parallel-axis theorem but had trouble making intuitive sense looking at it's derivation and statement. My confusion is that how is the moment of inertia about the center of ...
Bhavya Jain's user avatar
3 votes
1 answer
89 views

How does the definition of a rigid body imply constant distance from the center of mass?

Let there be a system of N point-particles in 3D space, this system is a rigid body. The general definition of a rigid body is $ \mid r_{i}-r_{j} \mid$=constant $\forall i,j$ In one of the books I was ...
16π Cent's user avatar
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0 answers
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Proof angular velocity is invariant to translation on rigid body [duplicate]

My understanding is for a rigid body the angular velocity between two points fixed on the body is the same for all points. In other words the angular velocity vector would be the same. I can't find a ...
FourierFlux's user avatar
1 vote
1 answer
297 views

Why isn't energy conserved for this particle?

The picture below shows a particle $A$ linked to a disk through a massless rod. The rod can freely turn, with no friction, around a fixed axis that goes through the center of the disk. The system is ...
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