PASCO ME-8930 SMART TIMER - Manual (Page 32)

Smart Timer 012–06734A
28
least three times and record the average values for weight of the hanging mass and
acceleration in Table 4.2.
3. Using calipers, measure the diameter of the pulley about which the thread is wrapped
and calculate the radius.
4. Since in step 2, 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. This rotational inertia can be
subtracted from the total, leaving only the rotational inertia of the ring. To do this, take
the ring off the rotational apparatus and repeat step 2 using a hanging mass of
approximately 30 g.
5. 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 4.4.
6. Repeat steps and 2 and record the data in Table 4.2.
Figure 4.4
Disk mounted vertically
rotating shaft
“D” hole of
rotational disk
“A” base
rotational disk
Ring and Disk
Disk Alone Disk Vertical
Combined
Friction Mass
Hanging Mass
Hanging Mass–
Friction Mass
Acceleration (a)
Table 4.2. Experimental Rotational Inertia Data