What Happens to Angular Speed When Moment of Inertia Increases?

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When a small object lands on a spinning disk, increasing its moment of inertia from I to 1.5I, the angular speed changes due to the conservation of angular momentum. The initial angular momentum is calculated as L = Iω, where the initial speed is 18 rad/s. The correct application of conservation of angular momentum shows that the new speed should actually decrease, not increase, as the total angular momentum must remain constant. The calculation presented, which suggests the new speed is 27 rad/s, is incorrect. Therefore, the new angular speed after the object lands will be lower than the initial speed of 18 rad/s.
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A large flat disk with moment of inertia I is spinning with angular speed 18 rad/s
a small object lands on the disk and changes the moment of inertia to 1.5I

what is the new speed?

i used L=I\omega to give me 18*1.5=27 rad/s

i used this because L is the angular momentum of the disk and has a relationship with the angular speed.

Is this correct?
 
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ghostbuster25 said:
A large flat disk with moment of inertia I is spinning with angular speed 18 rad/s
a small object lands on the disk and changes the moment of inertia to 1.5I

what is the new speed?

i used L=I\omega to give me 18*1.5=27 rad/s

i used this because L is the angular momentum of the disk and has a relationship with the angular speed.

Is this correct?

Do you have an equation showing the conservation of angular momentum ie the angular momentum before and after the object lands on the disk? If the moment of Inertia of the item with angular momentum increases, should the angular speed also increase? don't think so...
 
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ghostbuster25 said:
A large flat disk with moment of inertia I is spinning with angular speed 18 rad/s
a small object lands on the disk and changes the moment of inertia to 1.5I

what is the new speed?

i used L=I\omega to give me 18*1.5=27 rad/s

i used this because L is the angular momentum of the disk and has a relationship with the angular speed.

Is this correct?

I think answer is incorrect.
By the law of conservation of momentum,
disk initial momentum+object initial momentum =(disk+object) final momentum
object initial momentum is zero.
 
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