Physics Demo Number: 117

Approximate

Run Time: 10 min

Dominoes For Chain Reaction ( Exponential Release of Gravitational Potential Energy)

Demo Description

Stand a scaled set of dominoes on their ends.

Place them at spacings corresponding to a metal template.

Knocking the tiny one over with a tiny force leads to a chain reaction of falling dominoes.

 

Scientific Principles

  • An example of an exponentially increasing release of gravitational potential energy in a carefully staged chain reaction of nine rectangular- parallelepiped toppling dominoes, each of whose mass increases over the one before it by (3/2)^4, so that the net increase in released gravitational potential goes as (3/2)^32 or about 431,000.

Equipment

  • Nine Lucite dominoes, wrapped in electrical tape to prevent chipping and to optimize frictional contact between each pair.

  • Metal plate with center line and positional template for standing the dominoes in their appropriate initial positions.

  • A dramatic option may be added by using the dust explosion apparatus , triggered by the  last domino toppling onto a  rubber air bulb. Then a good bit of chemical energy is released at the end along with some extra acoustical energy and a flame.

 

Equipment Location

  • Dominoes are stacked in [E-4-3].

  • Metal template is flat on wall to left of [E-4-6].

  • Dust explosion apparatus is in kit (117) on [E-4-2].

 Instructions


The first photo shows the template for alignment of the nine dominoes placed on the lecture cart.

The next photo shows the result of placing the dominoes on the template.


The next picture shows the result of inducing the tiny domino on the right in the second photo to fall over (perhaps with a blow from a tiny piece of string) and strike its neighbor to the left, which produces a chain-reaction of falling dominoes.


Be sure that no objects or body parts are residing in the area where the big red domino will land, unless they are capable of absorbing 35J of kinetic energy without structural damage.

The dominoes live in [E-4-3] column, and the template lives nearby to the dominoes next to [E-4-6].

The fourth picture shows the dust explosion apparatus.

Writeup created by David A. Burba
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