PASCO PS-2120A User Manual
Experiment Guide
Sensor Plug
Alignment
tab
PASPORT
input port
850 Universal Interface
Capstone Hardware Setup panel
Rotary Motion
Sensor icon
850 Universal
Interface
013-13496A
Rotary Motion Sensor
PS-2120A
Contents
Using the Rotary Motion Sensor with Data Acquisition Software..........................................................................1
Experiment 1: Rotational Inertia of a Point Mass....................................................................................................3
Experiment 2: Rotational Inertia of Disk and Ring .................................................................................................5
Experiment 3: Conservation of Angular Momentum ..............................................................................................7
Using the Rotary Motion Sensor with Data Acquisition Software
• Plug the Sensor Plug into a P ASPORT input port of
a PASPORT-compatible PASCO interface (such as
the 850 Universal Interface, Xplorer GLX, or
SPARK Science Learning System (SLS)).
• Turn on the PASPORT-compatible interface.
• For the PASPORT-compatible interface, start the
PASCO Capstone software.
• For the SPARK SLS, if the sensor is plugged in, the SPARKvue software will start automatically when you
turn on the interface. The SPARKvue software will show the SPARK SLS Home Screen with the Rotary
Motion Sensor.
PASCO Capstone Setup
• In PASCO Capstone, click “Hardware Setup” in the Tools
palette to open the Hardware Setup panel. Confirm that the
Hardware Setup panel shows the interface you are using
and the icon of the Rotary Motion Sensor.
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PS-2120A Contents
Create a Graph display
Graph display
icon
Click the “Select
Measurement”
menu button
Select “Angular Velocity”
Click “Record”
Click “Stop”
• Set up a data display. For example, drag the Graph icon
from the Displays palette onto the workbook page, or double-click the icon to create a Graph display..
• Set up the Graph display to show Angular Velocity (rad/s) on the vertical
axis. Click the “Select Measurement” menu button on the vertical axis
and pick Angular Velocity (rad/s) from the menu. Time (s) automatically
shows on the horizontal axis.
• Click ‘Record’ in the lower left corner of the PASCO Capstone window
to begin recording data. (The “Record” button changes to “Stop”.)
• Turn the shaft of the Rotary Motion Sensor back-and-forth. V iew the data
• Click “Stop” to end data recording.
• SETUP: For detailed information on setting up the data acquisition software and recording data,
in the Graph display.
refer to the User’s Guide and the online help for the data acquisition software.
Experiment Guide
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PS-2120A Contents
SPARK SLS Home Screen for
the Rotary Motion Sensor
Press
Show
Press “Angular
Velocity”
Press “Angular Velocity” and
then press “Show”
Press “Start”
Press
Start
Turn the Rotary Motion
Sensor shaft
SPARK SLS Setup
• In the Home Screen, press “Angular Velocity” and then
press the Show button ( ) to open a graph display.
• Press the Start button ( ) to begin recording data.
Turn the shaft of the sensor and view the data in the display.
• Press the Stop ( ) button to end data recording.
• SETUP: For detailed information on setting up the
data acquisition software and recording data, refer
to the User’s Guide and the online help for the data
acquisition software.
Technical Support
For assistance, contact PASCO:
Address: PASCO scientific
10101 Foothills Blvd.
Roseville, CA 95747-7100
Phone: +1 916-786-3800 (worldwide)
800-772-8700 (U.S.)
Web: www.pasco.com
Email: support@pasco.com
Experiment Guide
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Rotary Motion Sensor Contents
4
Experiment Guide
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PS-2120A Experiment 1: Rotational Inertia of a Point Mass
I
total
M
total
R
2
=
I =
rT=
FmgT– ma==
Tmga–=
Experiment 1: Rotational Inertia of a Point Mass
Equipment Required* Equipment Required*
PASPORT-Compatible Interface Rotary Motion Sensor (PS-2120A)
Mini-Rotational Accessory (CI-6691) Mass and Hanger Set (ME-8979)
Base and Support Rod (ME-9355) Triple Beam Balance (SE-8723)
Paper clips (for masses <1 g) Calipers (SF-8711)
*Click the equipment item to go to the PASCO web site.
Purpose
The purpose of this experiment is to find the rotational inertia of a point mass experimentally and to verify that
this value corresponds to the calculated theoretical value.
Theory
Theoretically, the rotational inertia, I, of a point mass is given by I = MR2, where M is the mass, and R is the distance the mass is from the axis of rotation. Since this experiment uses two masses equidistant from the center of
rotation, the total rotational inertia will be
where M
To find the rotational inertia experimentally, a known torque is applied to the object and the resulting angular
acceleration is measured. Since
where
the weight hanging from the thread that is wrapped around the 3-step Pulley.
where r is the radius of the chosen pulley about which the thread is wound, and T is the tension in the thread
when the apparatus is rotating.
Applying Newton’s Second Law for the hanging mass, m, gives
= M1 + M2, the total mass of both point masses.
total
= I,
is the angular acceleration, which is equal to a/r (a = linear acceleration), and is the torque caused by
(see Figure 1.1). Solving for the tension in the thread gives:
After the angular acceleration of the mass (m) is measured, the torque and the linear acceleration can be obtained
for the calculation of the rotational inertia.
Experiment Guide
5
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Rotary Motion Sensor Experiment 1: Rotational Inertia of a Point Mass
T
mg
a
Rod and Masses
3-Step Pulley
Rotary Motion
Sensor
Super Pulley with
Clamp
Hanger
and Mass
Thread
Support
Rod
Rod
Clamp
Figure 1.1: Rotary Motion Sensor and
Free Body Diagram
Super
Pulley
Figure 1.2: Super Pulley Position
Equipment Setup
1. Attach a mass on each end of the rod (part of the
Mini-Rotational Accessory) equidistant from the rod
center. You may choose any radius you wish.
2. Tie one end of a thread to a Mass Hanger and tie the
other end to one of the levels of the 3-step Pulley on
the Rotary Motion Sensor (RMS).
3. Mount the rod and masses to the pulley on the Rotary
Motion Sensor. Please note the orientation of the
3-step Pulley.
4. Mount the RMS on a support rod and connect it to a
PASPORT-compatible interface. Make sure that the
support rod does not interfere with the rotation of the
rod and masses. See Figure 1.1.
5. Mount the Super Pulley wish Clamp on the end of the
Rotary Motion Sensor.
6. Drape the thread over the Super Pulley such that the thread is in the groove of the pulley and the Mass
Hanger hangs freely (see Figure 1.1).
Note: The Super Pulley with Clamp must be adjusted at an angle,
so that the thread runs in a line tangent to the point where it leaves
the 3-step Pulley and straight down the middle of the groove on the
clamp-on Super Pulley (Figure 1.2).
7. Adjust the Super Pulley height so that the thread is level with
the 3-step pulley.
8. Connect the Rotary Motion Sensor to the interface and turn the
interface on.
Procedure
Part 1: Measurements for the Theoretical Rotational Inertia
1. Weigh the two ma sses from the ends of the thin rod to find the total mass M
Table 1.
2. Measure the distance from the axis of rotation to the center of the masses and record this radius in Data
Table 1
Data Table 1: Theoretical Rotational Inertia
Total Mass
Radius
and record the value in Data
total
6
Experiment Guide
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