Have you ever seen a ski jumping competition? Athletes slide down the ramps at speeds of more than 100 kilometers per hour and fly in the air for more than ten seconds. Why can you fly so far? Landing from a high place, why not fall?
Scientific audit:
Hu Bin (Dean and Professor, Winter Olympic Training College, Beijing Sport University)
At 19:00 on February 14, the first round of the Beijing Winter Olympics ski jumping men's team competition was held at the National Ski Jumping Center, and the Chinese team sent Zhen Weijie, Lv Yixin, Song Qiwu and Zhou Xiaoyang to participate in the competition of the event. After all four players completed their own test jumps, the Chinese team ranked 11th with 115.0 points, and did not qualify for the final round later.
Ski jumping is referred to as "snow jumping", athletes pedal skis along the artificial jumping slopes, take off at the starting point, the body in the air along the parabola until the landing slope, and glide to the stop area to terminate. It mainly evaluates the flight distance and action posture of the competition athletes, which is the ultimate event that combines speed, strength and technology. Let's take a picture to understand.
▲Ski jumping (Image source: Xinhua News Agency)
Ski jumping is a veteran-level competition at the Winter Olympics: it has been included in the competition since the first Winter Olympics in 1924. At the 2022 Beijing Winter Olympics, there are five categories: (men's/women's) 90-meter standard platform, (men's) 120-meter big jump platform and (men's) team competition, of which the team event is a new event, and 5 gold medals will be decided.
What is the concept of a height of 120 meters? The height of the Beijing Observation Tower, located outside the south gate of the Beijing Olympic Forest Park, is 246.8 meters, and the snow jumping from the high platform is equivalent to about half the height of the Beijing Sightseeing Tower directly, jumping without any protection measures, flying in the air for a few seconds before landing.
▲Comparison of the height of the Beijing Sightseeing Tower and the jumping platform (Source: Xinhua News Agency)
Ski jumping is mainly divided into four stages, namely the skiing stage, the jumping stage, the flight stage and the landing stage. In the sliding stage, the athlete slides down from the starting point, and the gravitational potential energy is converted into kinetic energy, and the greater the gravitational potential energy, the greater the kinetic energy of the transformation. In order to reduce the impact of air resistance, players often use a crouching position while extending their arms close to their bodies and extending backwards, all to provide faster speed for the take-off stage.
Enter the take-off stage and the flight stage, and fly farther becomes the ultimate goal of the competition. After years of exploration by athletes, a V-shaped classic posture of leaning forward and two skis separating forward has been developed, of course, there are also athletes who have developed other postures on this basis, with the purpose of flying farther.
The landing stage is the most difficult and dangerous part of ski jumping, but the far mobilizers can often "turn the danger into a disaster". So the question is, from a height of 100 meters, without any protective measures, why can athletes still be unscathed after landing?
▲Schematic diagram of high-altitude skiing (Image source: Xinhua News Agency)
Our usual sense of "throwing out" refers to the throwing of the object, the object moves along the parabolic trajectory, or lands in a vertical manner, no matter what kind of trajectory, the speed will be zero instantaneously after landing, and the force distribution of this violent deceleration will cause great damage to the object.
There is no need for a height of one hundred meters at all, and as far as ordinary people are concerned, "jumping" from a height of more than ten meters is enough to cause serious damage.
But for ski jumping, first, the ski jumping platform and the landing slope are calculated, so that the trajectory of the athletes when they jump and land is consistent with the trajectory of their parabola, and it is not easy to land vertically; second, the landing surface is sloped, and the slope of the slope decomposes the force in the horizontal direction, and the force of the downward fall and the force of the landing slope form an angle, and the impact force that should have been downward is converted into the acceleration force on the slope, and the athlete can land safely, and continue to slide for a period of time, using the ground friction to stop. Finally complete the game.
In terms of equipment, in order to reduce the degree of damage caused by falls, the material of ski suits is generally synthetic fibers, and the lining is also equipped with foam to cushion the impact of the ground. The maximum width of the ski is 11.5 cm, and the length is generally 1.46 times the height, which provides a good guarantee for stability when landing.
▲The ski suit for high-altitude skiing is generally made of synthetic fiber material, and the thickness cannot exceed 6 mm at the maximum, and the thinnest cannot be less than 4 mm. Ski jumping costumes are thickened at the knees, hips, and elbows (Source: Xinhua News Agency)
▲Ski jumping skis are wider and longer than alpine skiing and cross-country skiing, so that they can better use the wind to slide farther in the air (Image source: Xinhua News Agency)
▲Special gloves for high-altitude skiing (Image source: Xinhua News Agency)
▲High-altitude ski helmet (Image source: Xinhua News Agency)
▲High-speed ski special ski shoes are made of leather, good flexibility, can protect the ankle, while ski shoes also need to have a higher waist, the waist of the shoe leans forward, must not hinder the athletes from jumping (Image source: Xinhua News Agency)
The participants in the ski jumping competition are all professionally trained skiers. Their flexibility and coordination are better than ordinary people, and they have undergone professional training and mastered a large number of ice and snow sports skills. All of this, it's no surprise that athletes can "fly freely" in the snow.
Due to the difference in the angle of the ski jumping slope and the lifting angle at the end of the platform, as well as the difference in natural conditions such as temperature, temperature, wind direction, wind power and snow quality, the ski jumping competition only has the best result, but there is no world record. While we understand the knowledge of sports science and appreciate the wonderful competition, we must also praise these hard-working and brave athletes!
(This content is jointly produced by Beijing Science and Technology News and China Digital Science and Technology Museum)
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