In Part One of this series, I discussed in great and tedious detail the construction of a whip using videos and website descriptions from two amazing whip makers as the primary references.
In this essay, I wish to discuss HOW that structure, the steady taper, reduction in mass, and physics allow the whip handler to accelerate a small portion of the end of the whip beyond the sound barrier and make a small sonic boom with only a minimal amount of force and effort. It’s admittedly still hard for me to wrap my brain around even today; I barely lift and extend my arm, and that motion is amplified and focused to such a degree that the tip of the whip reaches a minimum speed of about 770 miles per hour.
Let me just say again for the record that my “Advanced Degree” is in communications. ANYTHING I know about engineering and physics is gleaned from brilliant minds who operate on a level of understanding that I can only see the shadow of. So in order to explain and illustrate the details of the process far better than I ever could, I present an amazing video that says everything I WOULD want to say if I really understood all of it.
In this essay, I wish to discuss HOW that structure, the steady taper, reduction in mass, and physics allow the whip handler to accelerate a small portion of the end of the whip beyond the sound barrier and make a small sonic boom with only a minimal amount of force and effort. It’s admittedly still hard for me to wrap my brain around even today; I barely lift and extend my arm, and that motion is amplified and focused to such a degree that the tip of the whip reaches a minimum speed of about 770 miles per hour.
Let me just say again for the record that my “Advanced Degree” is in communications. ANYTHING I know about engineering and physics is gleaned from brilliant minds who operate on a level of understanding that I can only see the shadow of. So in order to explain and illustrate the details of the process far better than I ever could, I present an amazing video that says everything I WOULD want to say if I really understood all of it.
This is an episode of the web series “Smarter Every Day” with Destin Sandlin, an American engineer who created the program to share his love of and excitement about scientific principles with amateur folks like me, (and if you’re an armchair scientist like me, you should DEFINITELY subscribe to his channel!) His guest in this episode is, dancer, choreographer, flow and fire artist, Guinness World Record holder, world-renowned whip artist, and Rocket Scientist, April Choi, (seriously, she’s an engineer with a Masters Degree in mechanical engineering, and is currently working for NASA. She’s a 21st Century “Buckaroo Banzai”)
So, if you haven’t already, go ahead and watch the episode...THE WHOLE THING...It's fantastic...
I’m a video professional who has dabbled in 3D modeling and animation since the mid-’90s, and the high-speed photography process and 3D motion capture are processes I’ve wanted to use for YEARS now to study the motion and dynamics of a whip. The setup I had in my head is the equivalent of Neanderthals banging rocks together compared to the brilliance of their experiment design.
This touches ALL the bases I always want to cover. In fact, it does so amazingly well that this essay in the current series won’t be as long as the previous one, which spent a lot of time just establishing the terminology that I’m going to use from here on out.
I’d already read the earlier studies they mention in the video and had been in touch with one of the mathematicians who modeled the movement of the whip in the studies from the University of Arizona in the early 2000’s Destin mentions in the video. I also recently had the opportunity to ask April a few questions about whip dynamics.
To summarize the basics, (which if you’ve already watched the video and/or read the “Supersonic Whips” section of this website, this will be review), whips are big, flexible levers. The energy you put into the handle-end is greatly amplified at the popper-end. Due to the structure of the whip as defined in the previous entry, those densely braided layers of leather or nylon are tightly packed, so friction between strands and between layers, while present, is negligible. So, we have a continuous “Channel” for the kinetic energy we impart to the whip through the motion of our arm and hand. So, energy isn’t being lost in a significant amount as the “wave” of kinetic energy rolls down the length of the whip, BUT the whip is steadily reducing in diameter and mass along the length to the tip. Consequently, the speed of the wave of energy rolling down the whip increases, and the tip accelerates past the sound barrier.
I do want to point out a couple of things that the video features but doesn’t specifically mention because they are relevant to what will be further discussed in the remaining essays in this series.
Destin discusses Conservation of Momentum toward the end of the video when talking about getting smacked with his phone charging cable, and how that relates to the motion of a cracking whip. Conservation of Momentum is Sir Isaac Newton’s Third Law of Motion. What I want to point out here are outlined in the closely-related Second Law, and has to do with the Conservation of Energy and the principles of Inertia.
First of all, I want to talk about Conservation of Energy: If you took a class on physical science in primary or secondary school, this concept was no doubt drummed into you: “Energy can neither be created nor destroyed, it can only be transformed into some other form of energy.” That’s exactly what’s happening when the whip cracks. The kinetic energy of the whip is being transduced into acoustic energy - sound energy - as the whip breaks the sound barrier and the energy is transferred to the surrounding air. Once the crack has occurred, the whip is essentially de-energized.
You can clearly see this in the video of April cracking the whip. It displays structure and tension as the loop rolls down the length of the whip, accelerating into the state when it cracks - followed immediately by what you could call a semi-rigid state, with the whip fully extended for a few milliseconds. After that, the whip relaxes and fluidly follows through or bounces back, relatively slack. The bulk of the energy is transferred to the air as the kinetic wave is transduced to sound, so between the sudden loss of energy and the shock drag from the concussion wave of the crack, the whip decelerates very rapidly.
This principle is the basis for the appearance of danger in the whip performances of old: The whip artist sends the tip of the whip downrange toward the target being held by their lovely assistant. The target shatters in a dazzling display of sound and fury. Wow! They have to be really accurate to do that - like a sharp-shooter! Then the whip artist wows them further by sending the tip of the whip out toward the lovely assistant and it cracks with the same sound and fury that obliterated the target just seconds before. But the whip only gently and elegantly wraps itself around the outstretched arm of the lovely assistant, leaving not a mark or a blemish on their bare skin. HOW’D THEY DO THAT? Simply by where they placed the crack of the whip: Place the crack near the target, it tears it apart. Place the crack AWAY from the target - and the whip, de-energized and decelerated, simply wraps around the target in a slow, elegant arc.
Second, I want to talk about Newton’s First Law of Motion, which concerns inertia. That law states, in Newton’s own words; “Every object persists in a state of rest or of uniform motion in a straight line unless it is compelled to change that state by forces impressed upon it.”
The important part of that to our discussion is “uniform motion IN A STRAIGHT LINE unless compelled to change by forces impressed upon it.”
Note that in the video that during the motion tracking experiment, there is a long strip of white marking tape along the floor defining the path that the whip should take and that April very skillfully keeps that whip moving straight along as it accelerates into the crack.
By the very nature of the physics involved, a well-made whip will hit precisely what it is aimed at every time unless some outside force acts upon it. All we really have to do is line everything up, start the flow of the whip, and then let it do the rest.
Almost ALL of the problems I see people having in nailing a routine or hitting a target is that they’re trying to force the whip to do what they want it to do rather than just setting up the scenario they desire, and then letting the whip do the work.
That is obviously easier said than done, as not everyone is as spot-on precise in placing that crack exactly where they want it like April can. But note that she is aligning the whip at the beginning of the motion, and just letting it roll on through. If you are trying to hit a target with a whip and attempt to course-correct when the whip is already moving out in front of you, it’s too late. You will probably miss, and the whip will not crack efficiently or effectively.
By the exacting construction methods and the physics involved, a well-made whip will behave consistently EVERY time. If the whip should miss its mark or behave erratically, the problem is either the environment in which you’re working or more often than not, “pilot error.”
The next three essays of this series will explore the best methods of working with the foundational material to eliminate that pilot error; discussing how to properly set the whip up to crack the way you desire, and then just get out of its way and let that happen. Once you have those fundamental concepts down, everything else is just practice and repetition. After that, you’re primed and ready to focus whatever style of whip-cracking you want to pursue, from two-handed routines to incorporating dance, to stunt work and simulated violence, to martial arts.
So, if you haven’t already, go ahead and watch the episode...THE WHOLE THING...It's fantastic...
I’m a video professional who has dabbled in 3D modeling and animation since the mid-’90s, and the high-speed photography process and 3D motion capture are processes I’ve wanted to use for YEARS now to study the motion and dynamics of a whip. The setup I had in my head is the equivalent of Neanderthals banging rocks together compared to the brilliance of their experiment design.
This touches ALL the bases I always want to cover. In fact, it does so amazingly well that this essay in the current series won’t be as long as the previous one, which spent a lot of time just establishing the terminology that I’m going to use from here on out.
I’d already read the earlier studies they mention in the video and had been in touch with one of the mathematicians who modeled the movement of the whip in the studies from the University of Arizona in the early 2000’s Destin mentions in the video. I also recently had the opportunity to ask April a few questions about whip dynamics.
To summarize the basics, (which if you’ve already watched the video and/or read the “Supersonic Whips” section of this website, this will be review), whips are big, flexible levers. The energy you put into the handle-end is greatly amplified at the popper-end. Due to the structure of the whip as defined in the previous entry, those densely braided layers of leather or nylon are tightly packed, so friction between strands and between layers, while present, is negligible. So, we have a continuous “Channel” for the kinetic energy we impart to the whip through the motion of our arm and hand. So, energy isn’t being lost in a significant amount as the “wave” of kinetic energy rolls down the length of the whip, BUT the whip is steadily reducing in diameter and mass along the length to the tip. Consequently, the speed of the wave of energy rolling down the whip increases, and the tip accelerates past the sound barrier.
I do want to point out a couple of things that the video features but doesn’t specifically mention because they are relevant to what will be further discussed in the remaining essays in this series.
Destin discusses Conservation of Momentum toward the end of the video when talking about getting smacked with his phone charging cable, and how that relates to the motion of a cracking whip. Conservation of Momentum is Sir Isaac Newton’s Third Law of Motion. What I want to point out here are outlined in the closely-related Second Law, and has to do with the Conservation of Energy and the principles of Inertia.
First of all, I want to talk about Conservation of Energy: If you took a class on physical science in primary or secondary school, this concept was no doubt drummed into you: “Energy can neither be created nor destroyed, it can only be transformed into some other form of energy.” That’s exactly what’s happening when the whip cracks. The kinetic energy of the whip is being transduced into acoustic energy - sound energy - as the whip breaks the sound barrier and the energy is transferred to the surrounding air. Once the crack has occurred, the whip is essentially de-energized.
You can clearly see this in the video of April cracking the whip. It displays structure and tension as the loop rolls down the length of the whip, accelerating into the state when it cracks - followed immediately by what you could call a semi-rigid state, with the whip fully extended for a few milliseconds. After that, the whip relaxes and fluidly follows through or bounces back, relatively slack. The bulk of the energy is transferred to the air as the kinetic wave is transduced to sound, so between the sudden loss of energy and the shock drag from the concussion wave of the crack, the whip decelerates very rapidly.
This principle is the basis for the appearance of danger in the whip performances of old: The whip artist sends the tip of the whip downrange toward the target being held by their lovely assistant. The target shatters in a dazzling display of sound and fury. Wow! They have to be really accurate to do that - like a sharp-shooter! Then the whip artist wows them further by sending the tip of the whip out toward the lovely assistant and it cracks with the same sound and fury that obliterated the target just seconds before. But the whip only gently and elegantly wraps itself around the outstretched arm of the lovely assistant, leaving not a mark or a blemish on their bare skin. HOW’D THEY DO THAT? Simply by where they placed the crack of the whip: Place the crack near the target, it tears it apart. Place the crack AWAY from the target - and the whip, de-energized and decelerated, simply wraps around the target in a slow, elegant arc.
Second, I want to talk about Newton’s First Law of Motion, which concerns inertia. That law states, in Newton’s own words; “Every object persists in a state of rest or of uniform motion in a straight line unless it is compelled to change that state by forces impressed upon it.”
The important part of that to our discussion is “uniform motion IN A STRAIGHT LINE unless compelled to change by forces impressed upon it.”
Note that in the video that during the motion tracking experiment, there is a long strip of white marking tape along the floor defining the path that the whip should take and that April very skillfully keeps that whip moving straight along as it accelerates into the crack.
By the very nature of the physics involved, a well-made whip will hit precisely what it is aimed at every time unless some outside force acts upon it. All we really have to do is line everything up, start the flow of the whip, and then let it do the rest.
Almost ALL of the problems I see people having in nailing a routine or hitting a target is that they’re trying to force the whip to do what they want it to do rather than just setting up the scenario they desire, and then letting the whip do the work.
That is obviously easier said than done, as not everyone is as spot-on precise in placing that crack exactly where they want it like April can. But note that she is aligning the whip at the beginning of the motion, and just letting it roll on through. If you are trying to hit a target with a whip and attempt to course-correct when the whip is already moving out in front of you, it’s too late. You will probably miss, and the whip will not crack efficiently or effectively.
By the exacting construction methods and the physics involved, a well-made whip will behave consistently EVERY time. If the whip should miss its mark or behave erratically, the problem is either the environment in which you’re working or more often than not, “pilot error.”
The next three essays of this series will explore the best methods of working with the foundational material to eliminate that pilot error; discussing how to properly set the whip up to crack the way you desire, and then just get out of its way and let that happen. Once you have those fundamental concepts down, everything else is just practice and repetition. After that, you’re primed and ready to focus whatever style of whip-cracking you want to pursue, from two-handed routines to incorporating dance, to stunt work and simulated violence, to martial arts.