Ring and Disk Set

Product Code: ME-3419


Demonstrate Conservation of Angular Momentum with this set of 2 disks, a ring of equal mass, and 3 alignment guides

To demonstrate conservation of angular momentum, a non-rotating ring is dropped onto a disk that is rotating on a Wireless Rotary Motion Sensor (PS-3220) or a PASPORT Rotary Motion Sensor (PS-2120). The angular velocity of the disk is recorded in real time and students can easily determine the angular velocities of the disk just before and after the ring is dropped.

Combining these velocities with the rotational inertia of the disk and ring, students can confirm that angular momentum is conserved.

An alignment guide is placed on top of the rotating disk and is threaded onto the shaft of the Rotary Motion Sensor. This guide helps to align the ring precisely when it is dropped onto the spinning disk.

For a more complete investigation of rotational inertia as well as torque, you may be interested in the Rotational Inertia Accessory (ME-3420) which contains everything included in this kit as well as a pendulum rod with adjustable “point” masses and a clamp-on super pulley.


  • Discs (2): 8.9 cm diameter, 100 g
  • Thin Ring: 8.9 cm outer diameter, 7.9 cm inner diameter, 100 g
  • Alignment Guides (3): 3.9 cm radius, 1.7 g

Support Documents

Rotational Inertia Accessory Kit Instruction Sheet