The bullwhip crack is a supersonic shock wave created by impedance matching
Evidence
The bullwhip is a spectacular example of impedance matching (figure 1.3). If most of the energy from the relatively heavy handle region can somehow be efficiently transferred to a light string (“popper”) at the other end, the popper will wind up moving very fast. Sudden impedance mismatches along the whip would reflect energy, so the bullwhip is gradually tapered and also carefully constructed so as to have no abrupt changes in density or stiffness. … A factor of 20 does not sound huge, until you realize it is easy to get the handle moving at 40 miles an hour (a fast baseball pitch is 100 miles per hour), and 20 times that is 800 miles per hour, or faster than the speed of sound at 770 miles per hour! The popper thus goes supersonic (faster than the speed of sound). A supersonic object traveling through the air creates a shock wave, a very sharp pressure pulse. … The pulse itself travels through the air at the speed of sound, but when it reaches the ear, it is heard as a loud bang. — Eric J. Heller, Why You Hear What You Hear- An…, 80
Categorization
Category: Causal Relationships
- CANDY: The bullwhip crack being a supersonic shock wave is a perfect bar conversation fact.
- XREF: Connects to the reader’s deep interest in how sound physically reaches the ear and becomes perception.
Broader Connections
- Boom-producing surface motion involves extreme acceleration but modest velocity
#qualifies(0.75) — Eric J. Heller, Why You Hear What You Hear- An…, 698 - Suddenness of displacement, not speed, determines whether a boom is audible
#complicates(0.75) — Eric J. Heller, Why You Hear What You Hear- An…, 695