Rotation of a non pivot object

[VHAHAHA]

my teacher told.me.that If a rotating uniform stick is falling, the axis of rotation is about the cm of the stick.
I don't understand why it is about the cm of the ball. I have searched on google and i found no answer.
Can anyone give me some reference so that I can read? Can anyone explain to me? Thank you

 

[UltrafastPED]

Try this: http://ocw.mit.edu/courses/physics/8-01sc-physics-i-classical-mechanics-fall-2010/rotation-and-translation/two-dimensional-rotation-and-translation-dynamics/MIT8_01SC_coursenotes27.pdf

 

[VHAHAHA]

i have read this note
but i still can't the answer
any tips?

 

[D H]

You can describe the motion of a rigid body as a combination of translation of some point fixed with respect to the rigid body and rotation about that point. That point? It's completely arbitrary. It doesn't even have to be a point on the object. It's a consequence of Euler's rotation theorem.

So why choose the center of mass? That is the one point for which translational and rotational motion decouple from one another.

 

[PJC01]

The concept of rotation can be a bit confusing, but let me try to explain it to you. When an object is rotating, it is moving around a fixed point called the axis of rotation. This axis can be anywhere within the object, depending on how it is rotating.

In the case of a non-pivoting object, such as a uniform stick, the axis of rotation is typically located at the center of mass (cm) of the object. This is because the center of mass is the point where all of the mass of the object is evenly distributed, and therefore it is the point where the object will rotate around.

Your teacher is correct in saying that if a rotating uniform stick is falling, the axis of rotation is about the cm of the stick. This is because as the stick falls, it is rotating around its center of mass, which is located at the cm of the stick.

As for references, you can look into the concept of rotational motion and the center of mass in any physics textbook or online resource. I would also recommend talking to your teacher for further clarification and examples. I hope this helps!