PASCO ME-8950A COMPLETE ROTATIONAL SYSTEM - Manual (Page 44)

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 6.2.
Finding the Acceleration of Track Alone
Since in Finding the Acceleration of Disk and Track the track is rotating as well as the disk,
it is necessary to determine the acceleration, and the rotational inertia, of the track by itself so
this rotational inertia can be subtracted from the total, leaving only the rotational inertia of the
disk.
1. To do this, take the disk off the rotational apparatus and repeat Finding the Acceleration of Disk
and Track for the track alone.
NOTE: 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 Track Alone.
Disk Using Ball Bearings (Free Disk)
Mount the disk upside-down at the same radius as before. Now the ball bearings at the center
of the disk will allow the disk to rotate relative to the track. Repeat Accounting For Friction
and Finding the Acceleration of Disk and Track for this case and record the data in Table 6.2.
Calculations
Record the results of the following calculations in Table 6.3.
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 fixed disk and track combined.
3. Calculate the experimental value of the rotational inertia of the track alone.
4. Subtract the rotational inertia of the track from the rotational inertia of the fixed disk and track.
This will be the rotational inertia of the fixed disk alone.
5. Calculate the experimental value
of the rotational inertia of the
fixed disk and track com-
bined.
6. Subtract the rotational iner-
tia of the track from the
rotational inertia of the free
disk and track. This will be
the rotational inertia of the
free disk alone.
7. Calculate the theoretical
value of the rotational iner-
tia of the fixed disk off
axis.
8. Calculate the theoretical
value of a point mass hav-
ing the mass of the disk.
9. Use a percent difference to
compare the experimental
values to the theoretical
values.
Rotational Inertia for Fixed Disk
and Track Combined
Rotational Inertia for Track Alone
Rotational Inertia for Fixed Disk
Off-Axis (experimental value)
Rotational Inertia for Free Disk
and Track Combined
% Difference for Fixed
% Difference for Free Disk
Rotational Inertia for Free Disk
Alone (experimental value)
Rotational Inertia for Fixed Disk
Off-Axis (theoretical value)
Rotational Inertia for Point Mass
(theoretical value)
Table 6.3: Results