Angular velocity and external forces

[SpaceExplorer]

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?

 

[SpaceExplorer]

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...

 

[rock.freak667]

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.

 

[rcgldr]

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.

 

[Rap]

rcgldr is right - you have to know if the mass removed also removed any angular momentum before you can answer the question.