The explosive crack of a bullwhip can frighten cattle into a pen and even keep lions and tigers at bay. From scientific investigations dating back nearly a century, researchers had concluded that whips make loud sounds when their tips attain supersonic speeds and send shock waves–little sonic booms–through the air.
That long-standing explanation may not withstand a new analysis, however.
Calculations by applied mathematicians Alain Goriely and Tyler McMillen of the University of Arizona in Tucson indicate that another part of the whip–a loop rolling down the whip's length–also goes supersonic when it's near the tip and begins to uncoil. This creates the whip's signature cracking sounds, they say.
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