Physics Dept. Demonstration Manual

DLD19 - Inertia Cylinder


To demonstrate conversion of gravitational potential energy into linear and rotational kinetic energy.

  • custom ramp
  • custom cylinder with a locking axle
  • ring stand with a three finger clamp (clamp oriented with single finger side down to fit into the hole in the end brace of the ramp)


The system has been designed such that the cylinder fits into the slot in the ramp (see Figure 1) with the cylinder supported by it's axle. When released, with the axle free, the cylinder moves rapidly down the ramp without rotating (only the low I axle rotates). On the other hand if the axle is locked, the cylinder rotates as it moves down the ramp at a much lower linear velocity.



  1. PE Converted to Linear KE Only

    Loosen the axle lock such that the axle is free to turn.

    Position the cylinder at the top of the ramp taking care that when released the cylinder will be run straight down the ramp without binding on the ramp's rails.

    Instruct the students to ready to observe how long the cylinder takes to reach the bottom of the ramp.

    Release the cylinder.


    The cylinder hit the bottom of the ramp with quite a thump. It is recommended that the demonstrator be ready to catch the cylinder at the bottom. DO NOT LET THE CYLINDER JUMP OFF THE END OF THE RAMP, ROLL ACROSS THE BENCH, THEN ONTO THE FLOOR.

  2. PE Converted to Linear and Rotational KE

    Tighten the axle lock such that the axle cannot turn independently of the cylinder.

    Position the cylinder at the top of the ramp and proceed a described in Step 1.


    See also demonstrations DRD2 and 2.1.