Olympic science

Excerpted from Zhao Zhizhen's Light of Olympic Science and Technology. Authorized by Mr. Zhao Zhizhen, the Scientific Squirrel Club will be published on the Internet, reproduced from: Scientific Squirrel Club [].

As an efficient "energy converter", the bow can convert 70% to 80% of elastic potential energy into kinetic energy of the arrow, and the "remaining" energy becomes the damping vibration of the bow.

The meaning of archery

White, black, blue, red and yellow, these five-color concentric circles are the "targets" in the archery field. The target diameter is 122 cm, and the bull's-eye diameter is only 12.2 cm. An athlete should shoot the 10 ring from 90 meters away, which is equivalent to standing in one goal of a football field and shooting an apple at the opposite goal. In other words, the size of the whole target looks like a thumbtack in front of you. It is really not an easy task to achieve "a hundred steps to penetrate the Yang" and not miss an arrow.

It is difficult to find a nation in the world, and bows and arrows have never been used in history. Cupid's "Golden Arrow" and "Lead Arrow" govern the love between heaven and earth. Robin Hood robbed the rich and helped the poor by the "magic arrow", and Hou Yi transformed the "ecological environment" by the "nine-day archery range". How many myths and legends in the East and West are related to bows and arrows? In the long years before the appearance of "hot weapons", bows and arrows have always been the most powerful military equipment. From hunting tools to war weapons to sports, the role of bows and arrows in human civilization has undergone fundamental changes.

1908 women's archery competition in London Olympic Games

1900 At the time of the Paris Olympic Games, archery was already an "old-fashioned" sports competition. The old-fashioned longbow is elegant and has become the first sound for women to enter the modern Olympic Games. 1920 archery was disqualified after the Antwerp Olympic Games because the host country did not have uniform competition rules. We should be deeply grateful to Ms. Inge Bliss. Under the leadership of the only female president of the International Single Sports Federation, the International Arrow Federation made unremitting efforts to finally return archery to the Olympic family in 1972. The American men's team won individual and team championships in Atlanta Olympic Games, and star shooter McKinney was known as the "evergreen tree" in archery. South Korea's "dream team", known as the "archery machine", once became the leader of women's archery in the world. China girl He Ying and her partner won the women's team championship for the first time at the 200 1 4th1World Championships.

In shooting, the flight of bullets is propelled by gunpowder or compressed gas. All the strength of archery comes entirely from human physical strength. Today, the recurve bow used in the Olympic Games is still the "direct descendant" of the traditional bow and arrow, which consists of a rigid handle, elastic upper and lower bow pieces and a tough bowstring. Under the action of the athletes' bow-holding arms and bow-pulling arms, the tension on the bowstring makes the outside of the bow stretched and the inside compressed, which leads to the bending of the bow, transforms the muscle contraction force into the elastic potential energy of the bow, and then suddenly releases the flight of pushing the arrow. Bow is actually an energy converter, which converts human physiological energy into kinetic energy of arrows. In the bending process of the bow, the moment borne by each section is different, and the farther away from the bow handle, the smaller the stress, which is why recurve bow designed the bow tip into a "retroflex" shape.

The ancients have long understood the truth that "the bow should be strong". In archery competition, the average strength of male players is about 50 kg, and that of female players is about 35 kg. A regular world championship requires 288 bows in four days. The cumulative strength of male players is nearly 8 tons, and that of female players is more than 5 tons. But a weightlifter can only lift 1.5 tons in a competition. It can be seen how heavy archery is. What is more difficult is that archers are in a state of "pulling without firing, jumping like a horse" most of the time, and the horizontal support of the bow and arrow system and the vertical support of the standing body form a "cross" stress structure, and the end of the body is as dry as a branch. This advanced "static balance" is really not built in a day.

Archery aiming is more difficult than shooting aiming, because there is only a sight on the bow without a "door", so it is impossible to find a ready-made "aiming baseline" like a gun. Suppose we take the bull's-eye as the origin to make the horizontal X axis and the vertical Y axis. When the bull's-eye, sight, the edge of bowstring and eyes are in a straight line, the vertical plane of the arrow's flying direction should be consistent with the "bow plane" and coincide with the Y-axis on the target, so that the arrow will be concentrated on the Y-axis. So, how to ensure that the arrow is close to the X axis on the target?

Every time an athlete pulls a bow, he will put his finger on the right side of the mandible. Some archers put a small "kiss button" on the bowstring, and kiss it with their lips every time they shoot an arrow, so that the bowstring "leans" on the midpoint of the nose, the person and the chin. This "leaning method" ensures a fixed "leaning distance" from the tail slot to the aiming eye, so it is easy to control the height of the arrow.

Ensuring the linearity of exertion is one of the essentials of archery. The resultant point of bow pushing, the hook point and the center point of elbow joint of bow pulling arm should be in a straight line. Athletes can't "hold the bow" with all their hands, but want to "push the bow" from the jaws of the tiger, just to ensure the approximate "point contact" between their hands and the bow instead of the widest "surface contact".

recurve bow

A seemingly insignificant small part, called "signal film", is a significant invention in the history of archery. This is a piece of steel on the bow handle, which is used to hold down the arrow shaft. The archer pulled the bow in place, the arrow slipped out, and the steel plate hit the bow handle in the rebound, making a crisp "click" sound. The signal film can accurately "monitor" the depth of the athlete's bow every time, ensure that the bow arm maintains the same tension, and capture the "best deployment time" through "voice control operation". In archery, the most important thing is the consistency of action. The skills formed by each player through painstaking efforts must be highly fixed and programmed, as accurate and repetitive as a machine, and will not be out of shape and deformed at any time.

People often use the "arrow off the string" to describe speed. The initial velocity of the arrow shot by recurve bow is about 240 kilometers per hour, which exceeds the bullet train. The speed of an arrow depends on the strength and efficiency of the bow, the shape, weight and surface area of the arrow. The arrow feathers bonded in different ways can make the arrow rotate around the longitudinal axis to ensure flight stability. As a flying body with large length and diameter, the acceleration from bowstring will make the arrow shaft flex and vibrate elastically, which will reduce the flight stability. However, compared with shooting, the arrow's "action" is too slow, the speed is only one tenth of that of a bullet, and it takes about 1 second to reach the range 70 meters away. If the initial velocity direction is "flat throwing" to the bull's-eye, the arrow will fall nearly 5 meters due to the gravity of the earth when it reaches the target. Therefore, archery must have an "elevation angle", so that the arrow can make an "oblique throwing action" and the "trajectory" can become an arched parabola. It is no wonder that the arrow target is placed at an angle of 15 degrees with the vertical direction of the ground, facing the "ten thousand arrows through the heart" with a "look up" attitude. By the way, today's arrow target is to sew up the coiled straw rope and wrap it in target paper, using the same material as Zhuge Liang's "grass boat borrows an arrow"

The arrow target forms an angle of 15 degrees with the vertical.

As an efficient "energy converter", the bow can convert 70% to 80% of elastic potential energy into kinetic energy of the arrow, and the "remaining" energy becomes the damping vibration of the bow. According to the research of experts in the history of science, the appearance of early human stringed instruments was inspired by the sound produced by the vibration of bowstring. As for the bow that plays cotton, it is more obvious that "everything happens for a reason." These miscellaneous sticks installed on the recurve bow are called "shock absorbers" in order to increase the static inertia and rotational inertia of the bow, thus reducing the displacement and vibration of the bow during deployment. And achieve the effect of "counterweight", so that the center of mass of the bow and arrow system is closer to the bow pushing point to maintain balance.

compound bow

At the 38th Archery World Championships held in Jakarta from 65438 to 0995, the compound bow, which has gone through many hardships, was finally approved as an official event by the International Archery Federation. This is a real "modern bow" invented by American Allen in 1969, but its "innovation" is precisely the combination of the wheel and the bow and arrow, the two oldest inventions of mankind. The compound bow is equipped with eccentric wheels at the ends of the upper and lower bow pieces. Based on the lever principle of the moving pulley, when the bow opening force reaches the maximum, it becomes more and more "energy-saving" with the increase of the pulling distance, and the force can be reduced by 70% when the bow is full. This not only enables athletes to aim with a bow in a more relaxed and comfortable state, but also enables women to cross the gap of physical strength and use a "hard bow" like men.

Compared with recurve bow's tension curve, because it is in direct proportion to the increase of the pulling distance, the force exerted by the bowstring on the arrow is sudden and decreasing. However, the acceleration force of the compound bow on the arrow changes from small to large, and gradually tends to peak, and the effective action distance is correspondingly extended, so that the arrow leaves the string faster and the flight trajectory is straighter. In addition, the compound bow no longer uses three fingers to hook and lay strings, but "pulls the trigger" and lets the "string laying person" do it for you. The use of optical sight and bubble level greatly improves the accuracy of archery. The compound bow embodies scientific wisdom everywhere, and it has quickly become popular all over the world in recent years. Sales have occupied more than 90% of the world bow and arrow market and become the most prosperous "mainstream" of the bow and arrow family. Although the Olympic Games has not accepted the compound bow as an official event, the 13 Paralympic Games held in Beijing in 2008 has given the green light to the compound bow for the first time.

Every year, more and more archery competitions are vigorously carried out all over the world. In the long-distance race, each group shot 6 arrows according to the best result, and the world record of holding a bow reached 1.220 meters. In the ground target competition, draw a large target with a diameter of 15 meters around the column erected on the ground, and the players shoot 36 arrows from 100 meters away to decide the outcome. Riding and archery is still a traditional competition loved by many ethnic groups, and it is a foregone conclusion that skiing and archery will officially enter the Winter Olympics. In the forest of modern sports, the vitality of archery is increasing day by day.

From craftsmen in ancient workshops to high-tech equipment in modern enterprises, from bamboo chips, horns and wooden poles to aluminum alloys, glass fiber reinforced plastics and carbon fibers, human beings have never stopped making bows and arrows for thousands of years. We may inevitably fall into nostalgia for the past and the pursuit of civilization. Bows and arrows come from our primitive ancestors and will be passed on to distant descendants.