A disk of rotational inertia I about the central axis shown in (Figure 1) is rot

Question

A disk of rotational inertia I about the central axis shown in (Figure 1) is rotating about this axis with initial rotational velocity ,i on low-friction bearings. A second identical disk is held at rest a few millimeters directly above the first disk and suddenly dropped. After some slipping, the two discs are observed to have a common rotational speed about the original axis of rotation. Part A What is the magnitude of the final rotational velocity of the combined disks? What is the magnitude of the final rotational velocity of the combined disks? ,f=,i4 ,f=,i22 ,f=,i2 ,f=,i2 SubmitMy AnswersGive Up Provide FeedbackContinue of 1 no title provided

Explanation / Answer

the moment of an disk is c*m*r^2
where c is a constant depending on the configuration of the object. In the case of a disk c=1/2

This is essentially a collision. using conservation of momentum
I1*0-I2*0=(I1+I2)*f

I1=.5*m*r^2 and I2=.5*m*4*r^2

put it all together

f=-3*0/5

the larger moment wins the battle and the combined disks rotate in the same direction and a lower velocity

b)
.5*(I1+I2)*f^2-.5*I1*0^2-.5*I2*0^2
or
3*9/25-3= -1.92 J

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