How Does Impact Affect Angular Momentum and Velocity in a Rotating Disk System?

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The discussion focuses on calculating the angular momentum and angular velocity of a rotating disk system after a lump of clay impacts it. The initial angular momentum of the system is determined by combining the disk's angular momentum with that of the clay just before impact. The moment of inertia of the disk is calculated using the formula I = 0.5 * m * r^2, yielding a value of 1.044 kg·m². After the clay sticks to the disk, the new angular momentum and angular velocity need to be computed to understand the system's behavior post-impact. The calculations emphasize the importance of considering both the disk and clay's contributions to the overall angular momentum.
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Homework Statement


A rotating uniform-density disk of radius 0.6 m is mounted in the vertical plane. The axle is held up by supports that are not shown, and the disk is free to rotate on the nearly frictionless axle. The disk has mass 5.8 kg. A lump of clay with mass 0.5 kg falls and sticks to the outer edge of the wheel at location A, < -0.36, 0.480, 0 > m. (Let the origin of the coordinate system be the center of the disk.) Just before the impact the clay has a speed 8 m/s, and the disk is rotating clockwise with angular speed 0.83 radians/s.



1) Just before the impact, what is the angular momentum of the combined system of wheel plus clay about the center C? (As usual, x is to the right, y is up, and z is out of the screen, toward you.)
LC,i = ?kg · m2/s

2) Just after the impact, what is the angular momentum of the combined system of wheel plus clay about the center C?
LC,f = ?kg · m2/s

3) Just after the impact, what is the angular velocity of the wheel?
omega vecf = ?radians/s


Homework Equations


I have no clue


The Attempt at a Solution


I don't know how to do it
 
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luckyg14 said:
1) Just before the impact, what is the angular momentum of the combined system of wheel plus clay about the center C? (As usual, x is to the right, y is up, and z is out of the screen, toward you.)
LC,i = ?kg · m2/s
Angular momentum has units like kg.m/s.
The angular momentum of the combined system about C is the sum of the individual angular momenta about C.
What is the moment of inertia of the disc about its centre?
 
I=.5*m*r^2
=.5*5.8*.6^2
=1.044
 
luckyg14 said:
I=.5*m*r^2
=.5*5.8*.6^2
=1.044
Right, but don't forget to include units.
You know the initial rate of rotation of the disc, so what is its angular momentum about its centre?
 
The book claims the answer is that all the magnitudes are the same because "the gravitational force on the penguin is the same". I'm having trouble understanding this. I thought the buoyant force was equal to the weight of the fluid displaced. Weight depends on mass which depends on density. Therefore, due to the differing densities the buoyant force will be different in each case? Is this incorrect?

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