Angular velocity and external forces

Click For Summary

Discussion Overview

The discussion revolves around the effects of changing mass on the angular velocity of a rotating ring, specifically considering the conservation of angular momentum and energy. The scope includes theoretical implications of mass change during rotation and its impact on angular velocity.

Discussion Character

  • Exploratory
  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • One participant suggests that if the mass of the ring changes, the angular velocity must change to conserve kinetic energy, as the moment of inertia is affected by the mass reduction.
  • Another participant agrees, stating that the change in mass leads to a change in inertia, which necessitates a change in angular velocity to conserve angular momentum.
  • A different viewpoint notes that any process altering mass would likely also influence momentum and energy, indicating that the system may not be closed.
  • One participant emphasizes the need to understand whether the mass change also affects angular momentum to determine the outcome accurately.

Areas of Agreement / Disagreement

Participants express differing views on the implications of mass change on angular velocity, with some asserting that angular velocity must change while others highlight the necessity of considering the overall system dynamics and conservation laws. The discussion remains unresolved.

Contextual Notes

There are limitations regarding assumptions about the closed nature of the system and the specifics of how mass change occurs, which are not fully addressed in the discussion.

SpaceExplorer
Messages
25
Reaction score
0
Suppose I have a ring of mass 'M' rotating about an axis passing through its center with constant angular velocity 'w', now if its mass changes by dm due to some unknown reason during rotation, will the angular velocity change, assuming no external force acts on it during any point of time?
 
Physics news on Phys.org
my intuition tells me that it must change since KE must be conserved, and for it to be so, the angular velocity must change as the moment of inertia changes with the reduction in mass, but I ain't sure, so pls reply...
 
SpaceExplorer said:
my intuition tells me that it must change since KE must be conserved, and for it to be so, the angular velocity must change as the moment of inertia changes with the reduction in mass, but I ain't sure, so pls reply...

Yes it will change due to conservation of angular momentum as well. If the mass changes, then the inertia changes, so in order to conserve the angular momentum, the angular velocity will change.
 
Whatever process that changed the amount of mass would probably also affect the amount of momentum and energy. Momentum and energy are conserved in a closed system, but if mass is being changed, it's not a closed system.
 
rcgldr is right - you have to know if the mass removed also removed any angular momentum before you can answer the question.
 

Similar threads

Undergrad Effects of External Torques on the Angular Momentum of Asymmetric Bodies
  • · Replies 3 ·
Replies
3
Views
2K
Undergrad Conservation of Angular Momentum vs a gyro at the North Pole
  • · Replies 16 ·
Replies
16
Views
1K
Undergrad Properties of angular momentum
  • · Replies 6 ·
Replies
6
Views
915
Undergrad Confusion about adding angular velocities
  • · Replies 4 ·
Replies
4
Views
2K
Undergrad Conservation of angular momentum during collisions
  • · Replies 3 ·
Replies
3
Views
3K
Undergrad Non-Constant Angular Acceleration
  • · Replies 6 ·
Replies
6
Views
3K
Undergrad Energy of spinning objects as axis of rotation moves
  • · Replies 1 ·
Replies
1
Views
1K
Undergrad Conservation of angular momentum in the iceskater example
  • · Replies 10 ·
Replies
10
Views
1K
Undergrad Angular velocity of a rod and what formula to use while solving.
  • · Replies 15 ·
Replies
15
Views
3K
Undergrad Writing an equation for torque around an arbitrary point on a body
  • · Replies 6 ·
Replies
6
Views
1K