Rotary Motion Sensor (Rob Vondrak)
Author
Rob Vondrak, Immaculate Heart High School
Sensor / Probe
This probe measures the rotational motion. (angular acceleration, angular velocity, angular position). This is the PASCO version, but Vernier also has one.
Sample Investigation
How does the position of mass on a rod affect it's ability to rotate? Or will applying the same force cause an objects of different shapes to move at different rates?Wind a string around the rotary motion sensor, attach a mass, and hang it over a pulley. This will provide a constant force/torque being applied to the rotary sensor. Attach a long rod with masses to the wheel of the rotary motion sensor. Release the hanging mass and let the rod begin to spin. Measure the angular acceleration of the spinning rod. Reset the experiment and adjust the position of the rod masses and record the angular acceleration again.
Independent variable: Mass position
Dependent variable: Angular acceleration
Constants: Net torque, mass of the spinning rod
Sample Data & Analysis and Interpretation
A constant net torque is being applied by the falling mass on the string. That torque will cause the rod (that has a unique moment of inerti
Photos
The Rotational Motion Sensor does not come with the rod and masses, that needs to be purchases separately.
a) to spin with a constant angular acceleration. By adjusting the placement of the masses on the spinning rod, you will change the moment of inertia of the rod and when the same net torque is applied, it will have a different angular acceleration.Looking at a graph of the Angular Acceleration vs Time, you can see that the angular acceleration has increases when the masses were moved closer to the axis of rotation. (note the green trial is negative because the rod was spinning in the opposite direction). The angular acceleration decreases when the masses are moved farther from the center of the rod, this is because the moment of inertia has increased.
Movies
Promotional video for the sensor