Physics Demo Number: 081

Approximate Run Time: 10 min

Races On Inclined Plane with Rotational Inertia As Judge of Outcome

Demo Description

Race equal-diameter and equal-mass aluminum disks down an inclined plane.

The open-center disk is thicker than the solid one to allow equal mass with equal diameter.

 

Scientific Principles

  • Rotational Inertia

  • Conservation of Energy

  • Rotational and Inclined Plane Dynamics

Equipment & Set Up

  • Aluminum disks

  • Spare metal shelf ( seen in left-hand photo below, is now replaced by a shop-made phenolic board, seen in right photo below.)

 

Equipment Location

  • Aluminum disks are located in Kit (081) on [F-3-2] .

  • Phenolic board is on wall as seen in right-hand photo below.

  • Blocks of wood are Standing on [F-3-2] next to Kit (081)


Instructions

The left photo shows two equal-diameter and equal-mass aluminum disks , which may be made to race down the spare metal shelf under them with the aid of some blocks of wood to incline the racing plane.

The disks have different thicknesses to allow equal mass with equal diameter.

They were custom-machined for us in the Science Shop.

The right photo shows the new shop-made phenolic board , now dedicated  to serve as the inclined plane for racing disks and rings.

This new plane hangs from its U-Handle on a bracket on the wall   next to  my desk-workbench.

Closer inspection of this photo reveals an automatic disk catcher at the handle end of the plane, and a dedicated white nylon  stepping ramp to set the plane angle.

(One can also see the top corner of a flat metal plate hanging behind the plane.  This plate can be laid on the lecture-hall cork-floor when one needs a hard-contact reaction force of the floor on a body dropped on the floor.)

Various other rolling candidates are in Kit (081) for other races.
  
Writeup created by David A. Burba
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