Concepts

Chain reactions

Overview

A chain reaction is simulated by an array of armed mousetraps loaded with ping pong balls.

Details

Equipment

• [1] Mousetrap array
• [1] Single mousetrap
• [43] Ping pong ball
• [1] Rubber ball
• [1] Plexiglas box
• [1] Short stick

Classroom Assembly

1. CAREFULLY arm the mousetrap array with the 42 ping pong balls. This takes 15 minutes or longer (if traps are accidentally set off) to accomplish and must be done ahead of time.

Important Notes

• It is very easy to set off mousetraps prematurely. Great care is required when arming the array of mousetraps, when dropping a ping pong on the array during the "unmoderated" portion of the demonstration, and when moving the array.

Script

Nucleus/Mousetrap Analogy:

1. Arm the single mousetrap with a ping pong ball keeping well away from the array.
2. Taking care to direct the single mousetrap away from the array, set off the single mousetrap with the stick. The ping pong ball will fly across the lecture hall.
3. Discuss the analogy between a nucleus and the mousetrap.

"Unmoderated" System:

1. With the Plexiglas cover off, drop a ping pong ball onto the array. One or two traps will go off, and their balls will fly across the room.

Chain Reaction:

1. CAREFULLY place the Plexiglas cover on the array.
2. Drop the rubber ball through the hole in the side. A chain reaction will occur and most traps will go off.

Additional Resources