PASCO PS-2120A Rotary Motion Sensor User Manual
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P S - 2 1 2 0 A
E x p e r i m e n t 1 : R o t a t i o n a l I n e r t i a o f a P o i n t M a s s
7
E x p e r i m e n t G u i d e
Part 2: Measurement for the Experimental Method
A. Finding the Acceleration of the Point Masses and Apparatus
1.
In the data acquisition software, create an experiment to measure the angular velocity (in radians per sec-
ond) versus time (in seconds) of the point masses and apparatus.
•
In PASCO Capstone, for example, drag the Graph icon from the Displays palette to the workbook. Select
“Angular Velocity (rad/s)” for the vertical axis, and “Time (s)” for the horizontal axis.
•
Click the Hardware Setup icon in the Tools palette to open the “Hardware Setup” panel. In the panel, click
the properties button (it looks like a gear wheel in the lower right corner).
•
In the Properties window for Linear Accessory, select
the size of the 3-step Pulley you are using. The
default setting is “Large Pulley (Groove)”. Click OK.
2.
Put a 50-g mass on the Mass Hanger and turn the
3-step Pulley to wind up the thread so the hanger is
just below the Super Pulley. Hold the 3-step Pulley.
3.
Click Record to begin recording data, and release the
3-step Pulley, allowing the hanger to fall.
4.
Caution! Click Stop to end data recording BEFORE
the hanger reaches the floor or the thread completely
unwinds from the 3-step Pulley.
5.
In the Graph display, select the region of the data that
represents when the Point Masses and Apparatus
were accelerating.
6.
In the display, select “Linear” from the curve fit
menu.
The slope, m, of the linear fit represents the angular accel-
eration (
) for the Point Mass and Apparatus
7.
Record the value of the slope, m, as the angular accel-
eration in Data Table 2.
8.
Using calipers, measure the diameter of the pulley
about which the thread is wrapped and calculate the
radius. Record the radius in Data Table 2.
In the previous procedure, the apparatus is rotating and
contributing to the total rotational inertia. The next step is
to find the rotational inertia of the apparatus by itself so
that this rotational inertia can be subtracted from the total.
Select Size of 3-step Pulley
Select “Linear” as the Curve Fit