Please answer A & B Unit 13- Rotational Dynamics- Post-lab I. Calculating unknow

Question

Please answer A & B

Unit 13- Rotational Dynamics- Post-lab I. Calculating unknown moment of inertia A. The procedure for Experiment 1 could be used to determine the moment of inertia about a particular axis for an oddly shaped object. Suppose the lower platter, with mass of 0.900 kg and radius of 0.350 m, is rotating with an angular speed of 4.50 rad/s initially. When the object with unknown moment of inertia l is dropped onto the lower plate, the two objects rotate together with angular speed of 1.35 rad/s. What is the moment of inertia of the oddly shaped object? B. In the Experiment 1 in the lab, was there any outside torque acting on the system of the two platters? How can you tell? If so, what force may be creating the torque?

Explanation / Answer

A.moment of inertia of platter I1=mr^2/2

I1=.9*(0.35)2/2=0.055kgm2

now no external torque is applied on the system, so angular momentum is conserved

suppose unknown object has I2 moment of inertia

so,

I1w1=(I1+I2)w2

0.055*4.5=(0.055+I2)1.35

so I2=0.128 kgm2

B.No,there wasn't any outside torque acting on the syste of two platters, because the force exerted on the platter by the object is internal force of the system.the same magnitude of force is also exerted on the object by the plate.

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