Researchers are studying how best to shoot a rubber band. For help, they turned to physics and high-speed video. What they learned offers tips for making a clean shot — without hitting your thumb!
There’s more than one way to shoot a rubber band. Alexandros Oratis and James Bird are mechanical engineers at Boston University in Massachusetts. These researchers focused on one particular technique. First, give a thumbs-up. Now put the rubber band around the tip of your thumb and pull it back with the fingers of your other hand. Then let go.
To make sure their shots were consistent, the researchers used a cylinder as a stand-in for a thumb. Then they filmed a close-up of the shot in slow-motion.
As a rubber band is stretched, tension builds within it. The scientists saw that when they let go of the band, a release of that tension quickly travels along the rubber toward the cylinder (see the video). The band itself also zings toward the cylinder. But it moves more slowly than does the release of its tension, the scientists learned.
As the band shoots forward, the cylinder (or thumb) can get in the way. Colliding with the thumb can send the band askew. But with the right technique, the release of tension makes the thumb duck out of the way before the rubber band can smack it. The band is now free to sail past. As it does, the rubber scrunches into a wrinkly shape.
By testing different shooting strategies, the researchers found some guidelines. First, don’t pull the band too tight. The extra tension makes the band fly faster, so the thumb doesn’t have enough time to get out of the way. And a wider elastic band is better. That’s because the thumb has to press harder against the wider band. When the band is released, the thumb falls away more quickly, making the band’s getaway easier.
Oratis and Bird just shared their new findings, January 4, in Physical Review Letters.