Disney produced a documentary promoting nuclear power in 1957 called Our Friend the Atom. It has been shown in countless high school science classes since then. The 53-minute film is available in segments on YouTube,  if you'd like to watch the whole thing. One part that stuck with us is the demonstration of a chain reaction using ping pong balls on mousetraps.

Our Friend the Atom (segment 4 of 5)

The mousetrap reaction begins about six minutes into this segment. After seeing it, many budding scientists worked to recreate it. Not because it was educational, but because it was so cool.
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Harvard

These guys set theirs into a plexiglass case, for safety and in order to retrieve all the parts easier. They posted an explanation of a nuclear chain reaction and an overview of how this contraption was built, in case you want to reproduce this effect yourself.
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Short and Sweet

I don't know who did this one, but just watch this guy jump!
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In Class

A desktop demonstration sends balls and traps everywhere!
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Touchstone

Touchstone Energy used the gimmick for an ad with 6,000 mousetraps and 8,000 ping pong balls.
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St. Mary's University

It only takes a second for the chain reaction to happen, but when the video is played in slow motion, you can see the magic. This was produced by St. Mary's University. They posted an explanation here.
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Popcorn

This one has the perfect music for the slow-motion replay!
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