Experiment 13
ROTATIONAL DYNAMICS

ANALYSIS


1.  From the acceleration data of procedure step 4 for the 0.030 kg driving mass in cell C16, use the equation below to calculate the moment of inertia I for the platform. The quantity r is the radius of the hub which should have been entered in cell F51. Record the moment of inertia value in cell C58 on the Worksheet. Enter the average error in cell E58.

2.  Repeat, using the average data of procedure step 10 for the 0.050 kg driving mass in cell C24. Record this value of I in cell C59. Enter the average error in cell E59.

3.  Average the two results for the moment of inertia, and record the value and its uncertainty in cells C61 and E61. You can regard this number to be the best value of the moment of inertia of the platform by itself.

Measured Moment of Inertia

4. 

a.  From the data of procedure 11b for the 0.090 kg driving mass in cell C36, use the above equation to calculate I for the combination of disk + platform. Record the value in cell C67, and the average uncertainty in cell D67. Determine the moment of inertia for the disk alone by subtraction as indicated below, and enter the result in cell E67 on the Worksheet.

b.  Repeat the same analysis, using the data for procedure 11c for the 0.160 kg driving mass in cell C44. Record the value in cell C68, and the average uncertainty in cell D68. Determine the moment of inertia for the disk alone by subtraction, and enter the result in cell E68 on the Worksheet.

c.  Average the two measured values of Idisk, and enter the result in cell E70. You can regard this number to be the best value of the moment of inertia of the disk.

Calculated Moment of Inertia

5.  From the dimensions and mass of the disk, calculate its moment of inertia, using the formula from any textbook. For a solid disk, the moment of inertia is given by:

Enter the calculated value in cell E73.

NOTE: The above analysis carries over exactly the same in the case where a ring is added instead of a solid disk. The only difference in this case is that the moment of inertia of a ring is: Iring = M R2.

6.  Calculate the percentage difference between the calculated and the measured values for Idisk obtained in cells E70 and E73, respectively. Enter the value in cell E75.

7.  Answer Question 1 on the Worksheet.

8.  Print out the completed Worksheet and turn it in to your instructor.