A force sensor measures the centripetal force exerted on a mass as it moves in a circle. A photogate can be used to measure the angular speed. Different masses can be added to the platform and positioned at variable radii. The platform can be driven by a falling mass. The apparatus also accommodates the Vernier Wireless Dynamic Sensor System or Go Direct® Force and Acceleration Sensor to measure force, which provides the best set of data. Sensors are sold separately.