Intro to Continuum Mechanics: Explaining Rotation

AI Thread Summary
In continuum mechanics, the displacement vector \(\delta\vec{\mu}\) describes how a vector \(\vec{\mu}\) changes position, represented by the equation \(\vec{\mu}'=\vec{\mu}+\delta\vec{\mu}\). The discussion highlights how the new position incorporates derivatives of \(\vec{\mu}\) with respect to spatial coordinates. The last component, \(\frac{1}{2}\left(\frac{\partial\vec{\mu}}{\partial x_i}-\frac{\partial\vec{\mu}}{\partial x_j}\right)\), is crucial as it represents the rotational aspect of the vector field. Understanding this component requires familiarity with the concept of curl in vector calculus, particularly in two dimensions. This foundational knowledge is essential for grasping the implications of rotation in continuum mechanics.
stanley.st
Messages
30
Reaction score
0
Hello!

I read somewhere about intro to continuum mechanics. There was a vector \vec{\mu} and displacement vector \delta\vec{\mu}. As vector \vec{\mu} move, it will get new position

\vec{\mu}'=\vec{\mu}+\delta\vec{\mu}

\vec{\mu}'=\vec{\mu}+\frac{\partial\vec{\mu}}{\partial x_i}\delta x_i=\vec{\mu}+\left(\frac{\partial\vec{\mu}}{\partial x_i}+\frac{1}{2}\frac{\partial\vec{\mu}}{\partial x_j}-\frac{1}{2}\frac{\partial\vec{\mu}}{\partial x_j}\right)\delta x_i=\vec{\mu}+\left[\frac{1}{2}\left(\frac{\partial\vec{\mu}}{\partial x_i}+\frac{\partial\vec{\mu}}{\partial x_j}\right)+\frac{1}{2}\left(\frac{\partial\vec{\mu}}{\partial x_i}-\frac{\partial\vec{\mu}}{\partial x_j}\right)\right]\delta x_i

Last component

\frac{1}{2}\left(\frac{\partial\vec{\mu}}{\partial x_i}-\frac{\partial\vec{\mu}}{\partial x_j}\right)

represent rotation. Can you explain me that? I don't understand this rotation.
 
Physics news on Phys.org
Look up the Curl of a vector in 2 dimensions

http://en.wikipedia.org/wiki/Curl_(mathematics )
 
Last edited by a moderator:
The rope is tied into the person (the load of 200 pounds) and the rope goes up from the person to a fixed pulley and back down to his hands. He hauls the rope to suspend himself in the air. What is the mechanical advantage of the system? The person will indeed only have to lift half of his body weight (roughly 100 pounds) because he now lessened the load by that same amount. This APPEARS to be a 2:1 because he can hold himself with half the force, but my question is: is that mechanical...
Some physics textbook writer told me that Newton's first law applies only on bodies that feel no interactions at all. He said that if a body is on rest or moves in constant velocity, there is no external force acting on it. But I have heard another form of the law that says the net force acting on a body must be zero. This means there is interactions involved after all. So which one is correct?
Thread 'Beam on an inclined plane'
Hello! I have a question regarding a beam on an inclined plane. I was considering a beam resting on two supports attached to an inclined plane. I was almost sure that the lower support must be more loaded. My imagination about this problem is shown in the picture below. Here is how I wrote the condition of equilibrium forces: $$ \begin{cases} F_{g\parallel}=F_{t1}+F_{t2}, \\ F_{g\perp}=F_{r1}+F_{r2} \end{cases}. $$ On the other hand...
Back
Top