PASCO ME-8950A COMPLETE ROTATIONAL SYSTEM - Manual (Page 38)

Complete Rotational System 012-05293F
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Measure the Radius
1. Using calipers, measure the diameter of the cylinder about which the thread is wrapped and calcu-
late the radius. Record in Table 5.2.
Finding the Acceleration of the Disk Alone
Since in Finding the Acceleration of Ring and Disk the disk is rotating as well as the ring,
it is necessary to determine the acceleration, and the rotational inertia, of the disk by itself so
this rotational inertia can be subtracted from the total, leaving only the rotational inertia of the
ring.
1. To do this, take the ring off the rotational apparatus and repeat Finding the Acceleration of Ring
and Disk for the disk alone.
NOTE: that it will take less “friction mass” to overcome the new kinetic friction and it is
only necessary to put about 30 g over the pulley in Finding the Acceleration of the Disk
Alone.
Disk Rotating on an Axis Through Its Diameter
Remove the disk from the shaft and rotate it up on its side. Mount the disk vertically by inserting
the shaft in one of the two “D”-shaped holes on the edge of the disk. See Figure 5.5.
WARNING! Never mount the disk vertically using the adapter on the track. The adapter is
too short for this purpose and the disk might fall over while being rotated.
Repeat steps Measure the Radius and Finding the Acceleration of the Disk Alone to
determine the rotational inertia of the disk about its diameter. Record the data in Table 5.2.
Calculations
Record the results of the following calculations in Table 5.3.
1. Subtract the “friction mass” from the hanging mass used to accelerate the apparatus to determine
the mass, m, to be used in the equations.
2. Calculate the experimental value of the rotational inertia of the ring and disk together.
3. Calculate the experimental value of the rotational inertia of the disk alone.
4. Subtract the rotational inertia of the disk from the total rotational inertia of the ring and disk.
This will be the rotational inertia of the ring alone.
5. Calculate the experimental value of the rotational inertia of the disk about its diameter.
6. Calculate the theoretical value of the rotational inertia of the ring.
"A" base
rotating shaft
"D" hole of
rotational disk
rotational disk
Figure 5.5: Disk mounted vertically