Science Photo Contest


Entry no. 5:  Sock shot from cannon

Photographed by Joseph DiVerdi

I was introduced to the pleasures of a "potato cannon" some time ago and wondered how fast those projectiles were moving. After setting up a few photo sensors, some simple circuitry, and a timing counter I found that my son's socks could be made to travel across the workshop at speeds of 300 to 500 MPH. It was a small step to build a fast strobe light, tie it to the circuitry, and capture some photographs. The photograph shown here is affectionately named the "Hammerhead Sock" and is beginning to unfurl as it whizzes past the camera at about 450 MPH. The exposure time is about 30 microseconds which is the duration of the flash, and ASA 400 film and a 50 mm f/1.8 lens were used. Over-the-counter photographic flash accessories provide light pulses which are fifty to one-hundred times longer. In some other experiments,loosely crumpled aluminum foil balls were seen to go supersonic.

A detailed description of the entire project can be found at http://xtrsystems.com/strobe