In this experiment designed for use with PASCO Capstone software, students discover the relationships between centripetal force, mass, velocity and radius. The force and velocity are directly measured with sensors and the mass and radius can easily be changed.
The rotating arm features a groove with 2 captured masses along its length. One of the masses is free to move along the length of the groove. The "free mass" is connected to a small cable that runs under a pulley in the center of the arm and up to a Force Sensor. A ball-bearing swivel is used to ensure the cable does not tangle as the arm rotates. The other mass is placed the same distance from the center as the free mass; thereby balancing the arm. A flag attached to the bottom of the "fixed mass" passes through the photogate once per revolution, calculating the angular and tangential velocity of the mass.
The Force Sensor and Photogate allow accurate and repeatable measurements of force and velocity. Key variables (mass, radius and velocity) can be easily changed to discover their relationship to centripetal force.