What Causes Rotation of Rigid Bodies?

AI Thread Summary
The discussion centers on understanding the causes of rotation in rigid bodies, particularly when they rotate about a fixed axis. It highlights that in a rigid body, all atoms or molecules are fixed in place relative to each other, which allows each point to sweep out a circular path during rotation. The concept of centripetal force is raised, emphasizing that this force is necessary for maintaining circular motion. The conversation also touches on the constraints that keep the particles in their positions, although the analogy of a string is questioned in the context of rigid bodies. Overall, the key takeaway is that the fixed arrangement of particles within a rigid body enables consistent rotation around a fixed axis.
Amar.alchemy
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Hi All,

I don't know whether this question makes any sense or not anyhow i will ask. For example, consider a ball which is attached at the end of the string and let us assume that this ball rotates in the uniform circular motion. Then the reason it rotates in uniform circualar motion is its tangential velocity and radial accelaration(ie perpendicual component of accln).
Now consider a rigid body which rotates with constant angualr velocity about the fixed axis. My question is what makes the rigid body to rotate about the fixed axis?? kindly explain me.
 
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Amar.alchemy said:
Now consider a rigid body which rotates with constant angualr velocity about the fixed axis. My question is what makes the rigid body to rotate about the fixed axis?? kindly explain me.

Are you asking where the centripetal force comes from? If we assume the body is rigid, we are saying that every atom or molecule within it is fixed in place and cannot move relative to the others (due to chemical bonds or whatever). So every point particle that comprises that object individually sweeps out a circle around the axis of rotation. The radius of said circle depends upon how far away that point particle is from the axis. These individual motions together constitute a rotation of the entire body.
 
cepheid said:
Are you asking where the centripetal force comes from?

Exactly...
So what make these point particles to go around the fixed axis??
 
Amar.alchemy said:
Exactly...
So what make these point particles to go around the fixed axis??

The imposed constraint via the string.
 
Cyrus said:
The imposed constraint via the string.

In rigid bodies where does the sting comes??:confused:
 
Amar.alchemy said:
In rigid bodies where does the sting comes??:confused:

I don't understand what you're asking.
 
Amar.alchemy said:
In rigid bodies where does the sting comes??:confused:

This was mean to be my answer to that question:

cepheid said:
If we assume the body is rigid, we are saying that every atom or molecule within it is fixed in place and cannot move relative to the others (due to chemical bonds or whatever).

Every point is fixed in place relative to the others. Therefore, when you rotate the body, every point sweeps out a circle that is dictated by its (unchanging) position within the body. Do you understand?
 
Ya, thanks :)
 

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