PASCO ME-9341 INTRODUCTORY ROTATIONAL APPARATUS User Manual
Page 34
Introductory Rotational Apparatus
012-03051F
30
0.15
0
5
10
15
20
TIME (SEC)
0.2
0.25
VELOCITY VS. TIME
M = -0.007076
±
0.00001571
B = 0.2472
±
0.0001405
R = -0.9997
VELOCITY
(M/S)
0
Calculations
frictional
average
h
2
(avg)
GPE (J)
d (m)
theta (rad)
torque (Nm)
torque
B.P. + pulley
0.477
-0.043
0.888
59.18
-0.00073
0.569
-0.061
0.990
65.98
-0.00092
compare
0.595
-0.069
1.022
68.11
-0.00102
-0.00104
with
0.603
-0.083
1.042
69.44
-0.00120
below
0.603
-0.093
1.048
69.84
-0.00133
B.P. only
0.575
-0.072
0.996
66.40
-0.00108
0.581
-0.101
1.006
67.07
-0.00150
-0.00132
0.599
-0.100
1.086
72.42
-0.00138
B.P. + disk
0.595
-0.108
1.042
69.47
-0.00156
-0.00156
A second method of measuring the friction was used for comparison. The falling mass and attatched string were
removed and the super pulley was used with the Motion Timer program. The base plate was initially spun by
hand, and the frictional deceleration was measured as the slope of the velocity vs. time graph. (see graph) The
frictional torque was calculated from this deceleration and the known rotational inertia of the base plate.
I = 0.01
ω
o
alpha
torque
average
B.P. + pulley
6.3575
-0.11244
-0.00084
6.4890
-0.11504
-0.00086
2.8102
-0.10378
-0.00078
2.2213
-0.12181
-0.00091
2.2008
-0.08772
-0.00066
-0.00080
1.2787
-0.10370
-0.00078
0.6177
-0.09142
-0.00069
2.2157
-0.10252
-0.00077
1.7819
-0.12055
-0.00090
3.7205
-0.11370
-0.00085
There is a 23% difference in the measured friction with these two methods; mostly due to the fact that the second
method does not include the friction of the pulley used to hold up the dropping mass.
Notes
Expect a fairly wide spread of results on this
lab. The friction of the system depends on
many factors which may not be completely
controlled, and a 10% variation between
successive identical measurements is not
uncommon.