PASCO ME-9341 INTRODUCTORY ROTATIONAL APPARATUS User Manual
Page 36
Introductory Rotational Apparatus
012-03051F
32
Notes – on Procedure
➂-➄ Rather than go through the process of releasing and engaging the smart pulley each time, I found it easier to
hold the pulley against the platter with a rubber band all the time. Either way works fine, though.
➈
I did not get consistent results when dropping the ring on the disk, due to the difficulty in centering the ring
each time.
Notes – on Analysis
object
ω
o
ω
f
I
o
I
f
L
o
L
f
% dif.
RKE
o
RKE
f
disk on B.P.
4.30
2.16
0.00750
0.01453
0.032
0.031
2.68%
0.069
0.033
4.00
1.92
0.00750
0.01453
0.030
0.027
7.00%
0.060
0.026
6.75
3.45
0.00750
0.01453
0.050
0.050
0.98%
0.170
0.086
4.06
2.01
0.00750
0.01453
0.030
0.029
4.08%
0.061
0.029
7.20
3.39
0.00750
0.01453
0.054
0.049
8.78%
0.194
0.083
5.14
2.73
0.00750
0.01453
0.038
0.039
-2.89%
0.099
0.054
Bar on B.P.
3.62
2.45
0.00750
0.01052
0.027
0.025
5.06%
0.049
0.031
2.88
2.02
0.00750
0.01052
0.021
0.021
1.61%
0.031
0.021
2.35
1.54
0.00750
0.01052
0.017
0.016
8.08%
0.020
0.012
1.88
1.34
0.00750
0.01052
0.014
0.014
0.02%
0.013
0.009
Bar on B.P.+disk
2.80
2.33
0.01453
0.01755
0.040
0.040
-0.51%
0.056
0.047
3.14
2.60
0.01453
0.01755
0.045
0.045
-0.01%
0.071
0.059
5.48
4.41
0.01453
0.01755
0.079
0.077
2.79%
0.218
0.170
2.24
1.87
0.01453
0.01755
0.032
0.032
-0.83%
0.036
0.030
Angular momentum is conserved, kinetic energy is not.
There is a bit of delay time between when the objects first touch and when they equalize their velocities, and it has
been suggested that friction in the bearings during this delay is a source of error. To investigate this, a rubber band
was placed on top of the base plate and the first part of the experiment was repeated.
This method was found to greatly decrease the delay time, and there is some improvement on the actual results.
(The angular momentum of the rubber band was neglected.)
Another method of analysis, which almost entirely eliminates frictional problems, is to extrapolate both linear
regions of the velocity graph completely across the graph, then measure the instantaneous distance between these
two lines as the difference in velocity before and after the collision.
object
ω
o
ω
f
I
o
I
f
L
o
L
f
% dif.
RKE
o
RKE
f
Disk on B.P.
2.86
1.50
0.00750
0.01453
0.021
0.021
-1.60%
0.031
0.016
(rubber band)
4.01
1.93
0.00750
0.01453
0.030
0.028
6.76%
0.060
0.027
3.01
1.56
0.00750
0.01453
0.022
0.022
-0.41%
0.034
0.018
5.47
2.83
0.00750
0.01453
0.041
0.041
-0.23%
0.112
0.058