Whip-Cracking Machine Reliably Breaks the Sound Barrier

We tend to think of breaking the sound barrier as a comparatively modern accomplishment, but on a smaller scale, cattle herders have been breaking it for centuries: the cracking sound …. Whip-Cracking Machine Reliably Breaks the Sound Barrier. Reliably getting a crack out of a whip takes skill and practice, though, which is why [Craig Turner] built a whip-cracking machine.

The first step was to build the whip itself, which was surprisingly complicated. Bullwhips taper down toward the end of the whip. As the whip uncurls during a crack, momentum passes down the whip; since the whip becomes continually narrower and lighter, conservation of momentum means that different stretches of the whip must move progressively faster.

To get this effect, [Craig] joined together a series of increasingly thin and light ropes. The heavy end of the whip terminated in an eyelet connected to a length of elastic shock cord. Stretching the whip back on the shock cord and releasing it whipped it around, resulting in a fairly reliable crack.