Angular velocity and external forces

Click For Summary
When a rotating ring experiences a change in mass while maintaining constant angular velocity, the angular velocity will indeed change due to the conservation of angular momentum. As the mass decreases, the moment of inertia also changes, necessitating an adjustment in angular velocity to conserve momentum. The process that alters the mass could also impact the system's momentum and energy, indicating that the system may not remain closed. Understanding whether the mass removal affects angular momentum is crucial for a definitive answer. Therefore, any change in mass during rotation will influence the angular velocity.
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.
 

Thread 'Mousetrap Car Energy efficiency'

For simple comparison, I think the same thought process can be followed as a block slides down a hill, - for block down hill, simple starting PE of mgh to final max KE 0.5mv^2 - comparing PE1 to max KE2 would result in finding the work friction did through the process. efficiency is just 100*KE2/PE1. If a mousetrap car travels along a flat surface, a starting PE of 0.5 k th^2 can be measured and maximum velocity of the car can also be measured. If energy efficiency is defined by...
View full post »

Similar threads

Undergrad Conservation of Angular Momentum vs a gyro at the North Pole
  • · Replies 16 ·
Replies
16
Views
1K
Undergrad Effects of External Torques on the Angular Momentum of Asymmetric Bodies
  • · Replies 3 ·
Replies
3
Views
2K
Undergrad Energy of spinning objects as axis of rotation moves
  • · Replies 1 ·
Replies
1
Views
1K
Undergrad Conservation of angular momentum during collisions
  • · Replies 3 ·
Replies
3
Views
3K
Undergrad Does a person standing up on a swing in oscillatory motion do any work?
  • · Replies 6 ·
Replies
6
Views
2K
Undergrad Writing an equation for torque around an arbitrary point on a body
  • · Replies 6 ·
Replies
6
Views
1K
High School The physics of flywheel launchers (like tennis ball shooters)
  • · Replies 60 ·
3
Replies
60
Views
5K
High School Rolling of non-deforming sphere on a non-deforming rough surface?
  • · Replies 4 ·
Replies
4
Views
2K
Undergrad Is angular momentum perpendicular to fixed axis of rotation constant?
  • · Replies 1 ·
Replies
1
Views
1K
Undergrad Why does a free rigid body rotate only about its COM when F(ext) is applied?
  • · Replies 7 ·
Replies
7
Views
2K