Becoming Batman
Page 18
Before coming back to Batman, I want to think of a more common example. Think about the mechanics—restricted just to the arm for now—of pitching a baseball or throwing a football. Once the arm is brought back in preparation for throwing, the basic motion involves rotating the shoulder, then bringing the upper arm forward. After this process is started you see that you are extending your elbow during the motion—but not at the beginning of the motion. Last, the motion of the wrist is added on to the motions at the shoulder and elbow. Then the football or baseball is released to move toward the target. The principle of summation of forces is really no different from the relative motion examples used in high school physics classes. You know the one where someone throws a ball at 50 mph while stationary on the ground. Next that same person throws the ball at 50 mph but this time while standing on the flatbed of a big truck that is traveling in the same direction at 50 mph. How fast is the ball traveling relative to the ground in the second case (neglecting air resistance, of course!)? Now we have an ordinary Joe who can pitch a baseball at 100 mph.
I said earlier that we needed to consider the motions of the body in addition to that of the arm. Using the example of baseball pitching again, this means that we have to pay attention to the fact that the trunk rotates and the player pushes with his legs. Actually, good pitchers throw the ball with their entire body, not just with one arm. Batman’s punches are no different. When he punches he uses his whole body, including the segments of his trunk and legs, added all together with his arm motions to hit the target. If he steps forward to punch, he is also adding together now the energy from his forward step onto that of his punching arm. All of this adds the motion of each segment together such that peak velocities are all added up for each segment. This means that Batman’s punch will hit the target with as high a velocity as possible.
Why is velocity so important? Well, what Batman is trying to develop in his kicking foot or punching hand—and also what a pitcher is trying to achieve with a baseball—is maximum kinetic energy, or energy of motion (recall our discussion in Chapter 6). Kinetic energy is defined as 1/2m × V2, where m is the mass of the object (hand, foot, baseball, etc.) and V is the velocity at which the object is moving. (See, I promised you some math!) To hit the target with the largest impact forces possible, the highest kinetic energy is needed.
In the example of a punch, Batman is really having a collision between his fist and the chest or face of Joker, Killer Croc, or Bane. In such a collision, the time of impact is very important. This brings us to a term from physics, impulse, which is defined as force × time. A small force applied over a long time can be the same impulse as a high force applied over a short time. Thus, this same impulse from both scenarios can create the same change in momentum of the object to which the force is being applied.
However, in the case of crime fighting, speed is often essential. So, Batman needs to move quickly with high forces to change the direction of his foes’ attacks as well as plant some debilitating blows of his own. Here we are talking about derivations from Sir Isaac Newton’s second law of motion: “The rate of change of momentum of a body is proportional to the resultant force acting on the body and is in the same direction.” This law applies to the forces acting within Batman’s body, as his muscles work together to produce movement. It also concerns forces Batman’s whole body applies to the evildoers who are the target of Batman’s controlling forces.
Now let’s talk about a term you may be more familiar with: “collision.” When you collide with another car, damaging yours, it is generally an accident. When Batman punches the Penguin or his henchmen, it is a deliberate collision. Luckily for Batman, the human body is nowhere near as rigid as a car! Remember our pitcher? His arm moves in segments, and the force of his pitch was the sum of the force of the segments. This provides much needed flexibility and reduces damage to ourselves when we collide with an object. However, at impact the muscles remain tense to provide rigidity to the fist so that maximum transfer of force and energy from Batman’s hand into the target occurs. As part of this, Batman also tries to strike through the target somewhat so that impact moves into the physical space occupied by Killer Croc or the Joker. Also, the targets themselves have some flexibility in the softness of their flesh and muscles and in the fact that they will move back on reflex when someone comes forward to punch them! Too bad the criminals are not made of wood or concrete! We’ll learn more about what happens when you collide with these substances later.
Something else to keep in mind regarding striking and kicking is in martial arts it is preferred to strike small targets using small parts of the body. This action increases the pressure of the attack because pressure is equal to the applied force divided by the surface area over which that force is applied (in a mathematical formula: pressure = force × area). Think of high-heeled shoes. Imagine someone putting a running shoe on one foot and a stiletto high-heeled shoe on the other. With which foot would you rather be stepped on? Obviously, the stiletto heel will hurt much more. But the force of gravity pulling down the mass of the woman in both cases is the same. The surface areas are different, though, and so are the pressures.
Good examples for fighting are knife hand and sword hand strikes (we will revisit the knife hand in the next chapter). The tips of the fingers are the striking surface with the knife hand and represent a very small surface area. In this way, maximum force is imparted to the target over a small area. Other examples include using the side edge of the foot instead of the sole of the foot for side kicks, the ball of the foot instead of the instep for front kicks, and the area of the first two knuckles only and not all four knuckles when punching.
Boards Don’t Fight Back
With all this in mind let’s return to some of the questions I led off this chapter with. How powerful are martial arts blows? In karate a good way to get a handle on this is to look at the practice of what is called tameshiwari, or test breaking. This practice follows on from the much older practice in Japanese swordsmanship known as tameshigiri, or test cutting. Tameshiwari refers to the test breaking of materials like wood and concrete to gauge the skill and preparation of the strikes applied. There are four things to consider in this analysis: the force generated, the peak velocity of the body part used, the energy generated by the blow, and the deformation of the material that is struck.
First off, it has been calculated that an expert in karate—and this would be similar for any of the striking arts—can generate a striking force greater than 3,000 N (in which N stands for newtons, a measurement of force used in the metric system), or approximately 675 pounds. Is that a large force? Well, to break materials of simple structure like wood requires a force of 670 N (about 150 pounds), while concrete needs 3,100 N (almost 700 pounds). To break bone such as that in the jaw requires a force of only 1,100 N (about 250 pounds).
However, in many altercations a broken jaw isn’t the biggest worry; it is getting a concussion (which we will look at more in Chapter 13). Forces in the range of approximately 800 N (about 180 pounds) applied for only eight milliseconds are enough to produce head accelerations of 80 g that can yield a knockout blow. Here the g measures the effects of acceleration; it is roughly equivalent to 10 meters (32 feet) per second squared. As with your car, acceleration here means something is going at an increasingly faster speed. To put the number 80 g in perspective, roller coasters usually have a maximum of 3 to 4 g for a few seconds. Fatal car accidents can have a measure of 80 g.
In addition to the magnitude of the force, the velocity of the hand that must be reached to break wood is about 6 meters (about 20 feet) per second, while that for concrete is 10.6 meters (about 35 feet) per second. Remember that to calculate velocity you need two things: how far something is going and how fast its speed is changing. This is determined by dividing change in distance by change in time. The thresholds of hand (or foot) velocities needed to break wood and concrete are shown in Figure 10.1. The plots shown there are for hand techniques, and it is eas
y to see that wood can certainly be broken with a lower velocity strike than can concrete.
Learning to break a single pine board of one-inch thickness with something like a hammer fist strike is pretty easy. Almost anyone can do it with a little practice. Referring to my training terms here, even “Bruce” could do it! However, to break numerous pine boards all stacked together or to break concrete requires much more skill. Back when I was a teenager I used to do breaking as part of demonstrations. The most I ever did was six unfinished pine boards (no spacers!) with a sword hand strike.
Figure 10.1. Fist velocity and the deflection (in millimeters for concrete and centimeters for wood) needed to break two objects. Modified from Wilk et al. (1982).
A lot of what we know scientifically about the physics of martial arts techniques has come from studies conducted by Michael Feld, Ronald McNair, and Stephen Wilk. The name of McNair may be familiar to you for a tragic reason. McNair was not only a gifted martial artist (fifth-degree black belt holder) and MIT-trained physicist, but he was also a NASA mission specialist on board the ill-fated space shuttle Challenger when it exploded on January 28, 1986. McNair had an interest in physics applied to martial arts and was involved in taking measurements of hand and foot velocities from experts in empty hand fighting. I have extracted some of their data into Table 10.1 to give you an idea about the peak velocities of Batman’s hands and feet when striking and kicking.
To give another reference, these kinds of impacts have been likened to the force you would receive from Batman if he hit you with a wooden club weighing about 6 kilograms (13 pounds), lightly padded, and swung at about 20 mph. Keep in mind that Babe Ruth, the “Sultan of Swat,” used a bat that weighed 1.5 kilograms (3.5 pounds) early on in his career but later used a one-kilogram (2.5-pound) bat. The bat that Barry Bonds used in 2007 to hit his record-setting 756th home run was 85 centimeters (34 inches) long and weighted about .9 kilogram (2 pounds). It is worth noting that elite baseball players can swing the bat with peak speeds of about 90 mph. An equivalent baseball bat impact for Batman’s kick or punch would need a Barry Bonds style bat swung at about 45 mph. Of course, hitting with a maple bat and hitting with a closed fist do not produce identical impacts. However, this at least gives you a ballpark—sorry, pun intended—idea as to how hard those empty hand hits would be.
So the forces and velocities generated by experts such as Batman are well able to break such seemingly hard objects as wood, concrete, and bone. Now let’s look at why Batman’s hand doesn’t break while he is dealing all these blows. It stands to reason that if the forces generated in a hand strike are large enough to break bone and concrete they should also break the hand, too, shouldn’t they? Well, it isn’t quite that simple because of the way the force is applied and the geometry of the part of the body that is used. For example, because the fist is really a collection of bones held together with muscle, tendon, and connective tissue, it compresses when it hits something instead of breaking. Your bones can actually withstand impact forces much higher than “harder” materials. Remember in Chapter 5 we learned that your bones are basically stretchy material (collagen) embedded with hard minerals. Because of the overall structure of the fist, it can actually withstand forces of up to 25,000 N (more than half a ton) without breaking! It has also been estimated that the foot can withstand two thousand times more force than can a concrete block.
TABLE 10.1. Maximum velocity of different martial arts techniques in meters per second
Let’s look at how this discussion of force translates into fighting strategies. In Western fighting such as boxing the intention is to impart a large momentum to the entire body mass of the opponent. Boxers both generate and receive repeated blows with high forces. A central strategy is to chip away at the opponent by applying punches to the body and slowly wearing the opponent down. This contrasts with the typical objective of most Eastern martial arts traditions in which a quick and expeditious finish to any altercation is the focus. Many of the empty hand traditions actually operate around principles that are similar to those from the weapons traditions, particularly those of cutting bladed weapons. In Japanese swordsmanship there is a concept called ikken hissatsu. This battlefield term means to kill with a single cut of the sword. It has become associated also with empty hand fighting. In modern application this doesn’t actually mean killing. It refers to decisive and successful action taken in a confrontation that ends the fight as quickly as possible. This doesn’t argue against the effectiveness of Western empty hand fighting, but it does speak to the difference in tactics and overall approach to be found when contrasted to Eastern martial arts.
Consider another sport in which the athlete is always on the giving—or receiving—end of blows: boxing. How do the padded gloves of the “sweet science” of boxing affect the severity of blows during a boxing match? The gloves reduce the peak impact forces of the blows yet also increase the time over which the forces are applied, resulting in an increase in the impulse (which we learned earlier in the chapter is equal to force multiplied by time). Smaller peak forces lead to reduced damage to hard tissues like bone and cartilage. However, an equivalent or greater impulse can lead to very large accelerations to body segments such as the head, which can be quite damaging to the boxer.
Despite the use of gloves and helmets in sport boxing, the risk of knockouts does not seem to be lessened. This is so even when increasing the padding in the gloves (220 to 280 grams, or eight to ten ounces, for example). The peak forces generated by professional boxers can be greater than 4,000 N (900 pounds). This level of force could induce an acceleration greater than 50 gs on devices mimicking the human head. This easily exceeds any threshold for a knockout.
In real fighting, however, a one punch knockout is very unlikely. This is the case for Batman as well. He talks about this in a story called “The Blockbuster Breaks Loose!” (Detective Comics #349, 1966). In this story Batman fights a huge mountain man—you guessed it, he’s the Blockbuster—bent on his destruction. In one series of exchanges Batman manages to knock out the powerful Block-buster with one sword hand strike (or “karate chop”). He is then shown saying “A one-punch kayo! Robin won’t believe this!” It is very interesting to note that in a few panels prior to this one-strike knockout, Batman’s hand was hardened by an unknown “calcium compound.” So, this probably had a lot to do with how he was able to dispatch his opponent with one blow!
How Many Minions?
Just for fun I am going to answer some questions rather than posing them for a change! First, the answer to the question what is the quickest punching motion Batman can make is as low as 140 milliseconds. If Batman struck his blows in this range he would be able to punch Bane seven times in one second. If instead of how many times he can punch one bad guy in one second, we asked how many bad guys he can punch in one second, then the answer is three. This assumes the bad guys aren’t dummies and don’t line up to fight Batman but encircle him instead! But what if the punches and kicks—medium range techniques as shown in Figure 9.4—aren’t enough and Batman finds himself in hand-to-hand range? Let’s see what happens with throwing and judo next.
Throwing Down the Batgauntlet
When we consider throwing and falling, we are really talking about balance and posture and about how to uproot, unbalance, and destabilize someone so that they can be thrown. The term “throwing” really describes just placing an opponent in an unstable posture where his balance is “broken” and then letting him fall to the ground. Of course, more “oomph” is added to the fall by active throwing from a position of strength. The founder of judo, Jigoro Kano (1860–1938), took his training in jujutsu and the principle of ju. The term ju can mean suppleness, gentleness, or even “easy,” but this term has to do with using the strength of an attacker against himself. That is, instead of opposing the force of an attacker, you redirect and use that force to add to his.
Remember earlier in the chapter when we looked at the pitcher and how each of the segments of his
throw adds up and contributes to the total force of his throw? Now we are imagining each person in a fight as one segment and that we add up their forces to make a combined force. Let’s say, for example, Batman has a maximum force of ten, and he is fighting Batgirl who can only generate a maximum force of five. (These numbers are just for illustration because their forces would be way higher than this!) There is no way for Bat-girl to defeat Batman using force on force in this case because Batman’s force is double hers. However, if Batgirl uses her force in the same direction as Batman, her force of five is added to the ten of Batman. This gives a total of fifteen. Now, Batman cannot withstand this blended attack since he can only resist with ten. In this way a weaker opponent can defeat a stronger one.
I have fallen victim to this over the years. I am a fairly solid 1.9-meter (6′2″), 94.5-kilogram (210-pound) man. Many times, visiting Japanese masters—who were much, much smaller than I am—have come to Canada to give clinics. Often I would be selected to help with a demonstration of some particular technique. Frequently, those demonstrations involved small pulls and pushes on my body. These were followed quite quickly by a look at the ceiling of the training hall! I am thankful I knew how to fall without injuring myself. In those cases my own attacking forces were used against me. That was OK, though. I got to learn how to do the techniques as well as how effective they could be firsthand.
Another key component in determining force—and one that beginners such as Bruce often overlook—is the force of gravity. This force is always acting straight down from the body or body segment. It is a constant that can be used by the skillful expert to easily unseat and unbalance an opponent. When trying to throw an opponent using the principles in judo or other throwing arts, you are always pushing and pulling in various combinations on the opponent. This will turn the person and push the center of mass outside his or her base of support. Once the center of mass is positioned outside the base of support, the person will begin to fall. If he or she cannot recover balance (by stepping, for example) a fall to the ground will probably occur. If you add a little extra push or pull to this, a fall is certain.