What Causes Rotation of Rigid Bodies?

Click For Summary

Discussion Overview

The discussion revolves around the mechanics of rotation in rigid bodies, specifically focusing on what causes a rigid body to rotate about a fixed axis. Participants explore concepts related to angular velocity, centripetal force, and the constraints that govern the motion of particles within a rigid body.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • One participant questions what causes a rigid body to rotate about a fixed axis, seeking an explanation of the underlying mechanics.
  • Another participant suggests that the centripetal force is a key factor, noting that in a rigid body, every point particle moves in a circular path around the axis of rotation.
  • A follow-up inquiry seeks clarification on the origin of the centripetal force acting on the particles within the rigid body.
  • Participants discuss the concept of constraints, with one suggesting that an imposed constraint (like a string) is necessary for rotation.
  • There is confusion regarding the analogy of a string in the context of rigid bodies, prompting further clarification about the nature of rigidity and the fixed positions of particles within the body.
  • One participant emphasizes that in a rigid body, the positions of atoms or molecules are fixed relative to each other, which dictates the circular paths of the points during rotation.

Areas of Agreement / Disagreement

Participants express uncertainty regarding the analogy of a string in the context of rigid bodies, indicating a lack of consensus on this point. The discussion remains unresolved as participants explore different aspects of the mechanics involved in rotation.

Contextual Notes

There are limitations in the discussion regarding the assumptions made about the nature of rigid bodies and the role of forces in causing rotation. The analogy of a string may not directly apply to all rigid body scenarios, leading to confusion among participants.

Amar.alchemy
Messages
78
Reaction score
0
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.
 
Physics news on Phys.org
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 :)
 

Similar threads

Undergrad Why does a free rigid body rotate only about its COM when F(ext) is applied?
  • · Replies 7 ·
Replies
7
Views
2K
Undergrad What Happens When a Rigid Body with a Fixed Point Moves Along a Closed Path?
  • · Replies 8 ·
Replies
8
Views
2K
Graduate Rigid body kinematic motion and rotation
  • · Replies 13 ·
Replies
13
Views
2K
Undergrad Intuition Behind Intermediate Axis Theorem in an Ideal Setting
  • · Replies 6 ·
Replies
6
Views
2K
Undergrad Rigid body mechanics and coordinate frames
  • · Replies 3 ·
Replies
3
Views
2K
Undergrad Inertia of body moving about two distinct parallel axes
  • · Replies 10 ·
Replies
10
Views
2K
Undergrad Rotation of a rigid body about external axis
  • · Replies 10 ·
Replies
10
Views
4K
Undergrad Does a rotating rigid body has single angular velocity.
  • · Replies 3 ·
Replies
3
Views
2K
Graduate Is the rotational KE of a rigid body considered as internal energy?
  • · Replies 30 ·
2
Replies
30
Views
4K
Graduate A doubt in the rotational analogue of F=ma
  • · Replies 3 ·
Replies
3
Views
2K