Wireless Rotary Motion Sensor
Experiment 1: Rotational Inertia of a Point
14
013-15949A
Equipment Setup
1.
Attach a mass on each end of the rod (part of the Rota-
tional Inertia
l
Accessory Kit) 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
Wireless Rotary Motion Sensor (WRMS).
3.
Mount the rod and masses to the pulley on the Wireless
Rotary Motion Sensor. Please note the orientation of
the 3-step Pulley.
4.
Mount the WRMS on a support rod. 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 with Clamp (part of the
ME-3420) on the platform of the Wireless 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.
7.
Adjust the Super Pulley height so that the thread is level with the 3-step pulley.
Procedure
Part 1: Measurements for the Theoretical Rotational Inertia
1.
Weigh the two masses from the ends of the thin rod to find the total mass
M
total
and record the value in Data
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
Part 2: Measurement for the Experimental Method
A. Finding the Acceleration of the Point Masses and Apparatus
1.
In the data collection software, create an experiment to measure the angular velocity (in radians per second)
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).
Total Mass
Radius
Rod and Masses
3-Step Pulley
Wireless Rotary
Motion Sensor
Super Pulley
with Clamp
Hanger
and Mass
Support
Rod
Figure 1.1: Rotary Motion Sensor and Free
Body Diagram
