Difference between circular motion and rotational motion

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Discussion Overview

The discussion explores the differences and similarities between uniform circular motion and rotational motion, focusing on their definitions, characteristics, and the forces involved. Participants examine how these concepts relate to angular and linear quantities, as well as the implications for analyzing motion in various contexts.

Discussion Character

  • Conceptual clarification
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • Some participants propose that uniform circular motion involves a body orbiting a central point with a centripetal force, while rotational motion describes how a body rotates around an axis.
  • It is suggested that in strictly angular motion, the center of mass does not undergo translational movement, contrasting with uniform circular motion.
  • Participants note that a body can experience both angular motion and linear translation simultaneously.
  • There is a discussion about whether centripetal force acts on every particle of a rotating body, with some asserting that intermolecular forces provide this centripetal force in a steel ball.
  • Some participants mention that both types of motion can be described using angular and linear quantities, although linear quantities may be less convenient for extended objects.
  • There is a suggestion that the choice between using angular or linear quantities depends on the specific problem and the information available.
  • One participant introduces a tangential topic about jet engines, indicating a potential interest in practical applications of these concepts.

Areas of Agreement / Disagreement

Participants generally agree on the definitions of uniform circular motion and rotational motion, but there are nuances in how these concepts are applied and understood. Some aspects remain contested, particularly regarding the role of centripetal force and the choice of quantities for analysis.

Contextual Notes

Some assumptions about the definitions of motion types and the nature of forces involved may not be fully articulated, leading to potential misunderstandings. The discussion does not resolve the complexities of analyzing motion in different contexts.

Who May Find This Useful

This discussion may be of interest to students and enthusiasts of physics, particularly those exploring concepts of motion, forces, and their applications in real-world scenarios.

Mr Davis 97
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I don't really understand the difference between uniform circular motion and rotational motion. I know that uniform circular motion deals with a body that is orbiting around a central point, with a centripetal force that is causing it to move in a circle. I know that rotational motion uses angles to describe how a body rotates around a central axis. However, aren't these basically equivalent? Each one involves a point revolving around a central axis. Is the real difference that rotation is described in terms of angles, and uniform circular motion is described in terms of linear acceleration and velocities?
 
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Mr Davis 97 said:
Is the real difference that rotation is described in terms of angles, and uniform circular motion is described in terms of linear acceleration and velocities?

Basically.

Uniform circular motion describes transitional movement around a fixed point, while angular motion describes how a body rotates about an axis. In strictly angular motion, the bodies center of mass doesn't undergo any translation movement.

You can have a body that undergoes angular motion while the center of mass undergoes a linear translation movement. (Move's in a straight line) You can also have a body that undergoes both uniform circular motion and angular motion.
 
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Student100 said:
Basically.

Uniform circular motion describes transitional movement around a fixed point, while angular motion describes how a body rotates about an axis. In strictly angular motion, the bodies center of mass doesn't undergo any translation movement.

You can have a body that undergoes angular motion while the center of mass undergoes a linear translation movement. (Move's in a straight line) You can also have a body that undergoes both uniform circular motion and angular motion.
Okay, that makes sense. I have another question. If we have a steel ball, and it is rotating about an arbitrary axis and is not in transnational motion, is there a centripetal force acting on every particle of the ball?
 
Yes, there is. The centripetal force is "provided" the inter molecular forces that keep the particles together in the steel ball.

And by the way, both types of motions mentioned in the OP can be described by angular quantities. And both can be described in terms of linear quantities as well.
For the spinning of extended objects, the linear quantities may not be so convenient but they are there.
 
nasu said:
Yes, there is. The centripetal force is "provided" the inter molecular forces that keep the particles together in the steel ball.

And by the way, both types of motions mentioned in the OP can be described by angular quantities. And both can be described in terms of linear quantities as well.
For the spinning of extended objects, the linear quantities may not be so convenient but they are there.
So the choice between tackling a problem in terms of angular quantities or linear quantities is determined by the information provided and which one would be easier to use in a specific case?
 
You might find it interesting to look into how jet engines work.
Turbofans are even more interesting.
 
Mr Davis 97 said:
So the choice between tackling a problem in terms of angular quantities or linear quantities is determined by the information provided and which one would be easier to use in a specific case?
Yes. Or you can use both even in the same problem.
In general the motion is a combination of translation and rotation, anyway.
 

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