Teacher guide featuring 15 labs designed for Advanced Placement Physics 1.
Students use a rotary motion sensor to determine the mathematical relationship between torque, rotational inertia, and angular acceleration of a rotating object.
How do net torque and rotational inertia affect the angular acceleration of a rotating object? Experimentally determine the mathematical relationship between net torque, rotational inertia, and angular acceleration of a rotating object.
The Structured version of this lab activity is divided into two parts: Part 1 – Students use hanging masses to apply torque to a rotating arm, oriented horizontally (see figure below). In each Part 1 trial, students keep the rotational inertia of the arm constant and measure its angular acceleration while increasing the amount of applied torque by adding more hanging mass. A plot of angular acceleration versus net torque will show a straight line, and from that, students are expected to recognize the proportional relationship. Part 2 – Students use a fixed hanging mass to apply a constant non-zero net torque to the same rotating arm used in Part 1 while measuring the angular acceleration of the arm; however, in each Part 2 trial they keep the applied torque (amount of hanging mass) constant and vary the rotational inertia of the rotating arm by adjusting the position of two masses fixed to the rotating arm. Rotational inertia is increased as the masses are positioned farther from the axis of rotation. Students calculate the rotational inertia of the arm in each trial and then calculate the inverse rotational inertia (1/rotational inertia). A plot of angular acceleration versus the inverse of rotational inertia will show a straight line, and from that, students are expected to recognize the proportional relationship. Students are then expected to combine the relationships outlined in each part into one mathematical expression relating the three variables.
The Ohaus Scout Pro Balance 2000g listed in the Materials and Equipment section is for classroom use, not individual lab stations.
This experiment may require software and an interface for data collection.