The Physics of Whip Cracking

I tried my hands on whip cracking in an Aussie sheep farm tour late last year.  Interestingly, whip cracking in Australia has gained enough prominence to be a competitive sport! I must admit that the whip is not my forte, as I could only get it cracking 10% of the time (when I am not hitting myself with it).  Staring at defeat, I decided to learn the science behind this in hope of conquering it some day.

It turns out a whip cracks because a sonic boom is created at its tip or topper. A sonic boom is created when an object travels at supersonic speeds such that its surrounding waves of air pressure are compressed into a single shock wave at the speed of sound. The logical question then: what is travelling so fast in the whip? Well, it's the tip.

Why? Conservation of momentum! Let's picture this: when you apply a force to a whip, the initial loop motion and wave are applied to the thong, which has a much larger mass than the whip's tip. It is worth noting that momentum is the product of the mass and speed of the moving object. The smaller the mass, the higher the speed, thus the lighter tip ends up moving extremely fast. In fact, a tip can reach Mach 2 and 30 times its initial speed when whipped properly. 

Now that I know the science behind whips, hopefully I will see improvement next time I get my hands on one.


-PTS

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