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Forums
Physics
Classical Physics
Mechanics
Calculate the change of angular velocity
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[QUOTE="Cutter Ketch, post: 6302187, member: 515910"] You apparently have a specific piece of demonstration equipment in mind, but we are not understanding what this equipment looks like or what you are doing with it. Could you post a diagram and ask your question using the diagram as a reference? That being said, it sounds like you have an apparatus consisting of a rotating structure and two masses on the rotating structure. While the device is spinning the two masses can be moved inward or outward closer to or further away from the axis of rotation. If I am understanding correctly, you want to know how to calculate the final angular speed after moving the masses given the initial speed and some knowledge of the moment of inertia of the structure and the mass of the weights. If I have that right, this should be a very simple calculation. You will need to know the moment of inertia of the structure. Usually this is a simple disk shape so that the inertia is easily calculated, or it is provided by the manufacturer of the demonstration equipment. Moments of inertia add, so with the added masses the total moment of inertia is: ##I_{struct} + m_1 r_1^2 + m_2 r_2^2 ## Often the masses have the same mass and are arranged so that they are always at the same distance from the axis. Then the inertia reduces to ##I_{struct} + 2 m r^2## The position of the masses r is what you are changing, and this in turn changes the moment of Inertia ##I_{initial} = I_{struct} + 2 m r_{initial}^2## Is changed to ##I_{final} = I_{struct} + 2 m r_{final}^2## Assuming negligible friction, momentum is conserved: ##I_{initial} {\omega}_{initial}= I_{final} {\omega}_{final}## [/QUOTE]
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Physics
Classical Physics
Mechanics
Calculate the change of angular velocity
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