Description: A chain reaction is simulated by an array of armed mouse traps loaded with ping pong balls.

42 mouse traps are mounted on a piece of plywood in a 6 by 7 array. Two ping pong balls may be positioned on each trap. It takes 15 minutes to arm and load the traps with no accidental events.

Demonstrate that a mouse trap stores energy and discuss the analogy between a nucleus and a trap. Start with a single trap. Arm it and load a ping pong ball, WELL CLEAR of the trap array. Ensure that the ball will fly AWAY from the trap array. Trigger the trap with a stick. The ball should fly across the lecture hall.

Next demonstrate what happens with an unmoderated sample. With the cover off drop a single ping pong ball onto the array. One or two traps should go off, with their balls flying across the room.

Finally demonstrate the chain reaction. CAREFULLY place the cover on the array. Drop a ball through the hole and watch. Use a rubber ball to ensure a good start (we have had dud reactions).

Cautions: Great care is required when setting the traps, and also to avoid setting off the reaction prematurely.

Concepts demonstrated: Chain reaction

Setup Time: Long and involved.

Difficulty/Commitment: Although not lengthy to perform, this demonstration should not be treated lightly owing to the difficulty in setting up.

Visibility: Visible. At some point we might try videotaping it and playing back the reaction in slow motion..

Related demonstrations:

References: PIRA #7D20.10
Video Encyclopedia 25-15
further references may be found here.