Did I Use the Right Approach for Conservation and Angular Velocity?

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Homework Help Overview

The discussion revolves around a problem related to conservation principles in physics, specifically focusing on angular velocity and the conservation of energy and momentum in a collision scenario involving a rotating object.

Discussion Character

  • Mixed

Approaches and Questions Raised

  • The original poster attempts to apply conservation of energy to find angular velocity but questions whether this is appropriate given the context of a collision. Some participants suggest that angular momentum conservation may be more relevant.

Discussion Status

Participants are exploring different conservation principles, with some suggesting that angular momentum should be used instead of energy. There is an ongoing examination of how to relate linear velocity to angular velocity, particularly in the context of the moment of inertia.

Contextual Notes

There is a note in the problem indicating that the door should be treated as a rod rotating about its end, which may influence the choice of equations and conservation laws to apply.

shaqtus
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Homework Statement


I need help with this question: http://img804.imageshack.us/img804/2278/unledsbg.jpg

For a, I got omega = 18.63 rad/s by using methods of conservation of energy. Can someone tell me if I did this right? If not, please help me out! To be honest, I thought I had to use conservation of momentum for this since it involves a collision, but its equations don't involve angular velocity.

Homework Equations



Conservation of energy/momentum

The Attempt at a Solution


a) omega = 18.63 rad/sec
 
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Energy is not conserved. But angular momentum is.
 
So does that mean I find v by means of conservation of momentum, and then use omega = v / r to find the answer? The reason I'm confused is because at the note at the bottom of the question, it says treat the door as a rod rotating about its end, which is a hint to use Inertia = (1/3)ML^2. Conservation of energy, not momentum, has inertia in its equation.
 
shaqtus said:
Conservation of energy, not momentum, has inertia in its equation.
Conservation of angular momentum will involve the moment of inertia.
 

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