Two masses, one of them fixed, the other free to move but attached to a larger mass weighing it down, are attached to a rod, which is rotated by a motor. If the rod rotates fast enough, the smaller mass on the rod lifts the larger mass underneath the device.
The device also has an in-built counter, which can measure the number of rotations the rod undergoes in a minute. These measurements can be used to corroborate the formulas for centripetal motion.
A more modern apparatus which uses Vernier data collection apparatuses to collect data on the centripetal force of the small mass as a function of angular velocity is also in use in the Physics labs.
Location: Older Welch Apparatus C2-4, Motor Q3-3, Newer Welch Apparatus Room 73