the resistance movement
speed, height, strength in battle is the core of modern sports, so sports is mechanics and physics in particular has a very closely related.The upcoming Beijing Olympic Games, both the strength of world sports contest, but also sports-related science and technology contest.
In this paper, the mechanical knowledge in the application of sport to the reader to make some simple introduction.If you are interested in this area, but also in the July 16 to September 7 at Chaoyang Park, between the Sony ExploraScience Science Museum entitled"The Ultimate Challenge 0.01 seconds - Something about the resistance movement & rdquo ; science exhibition, experience the magic of science and sports related!
What is resistance?
objects in the water or air, the fluid flow in the Games by the force on the object, the direction of this force is always opposite the direction of the movement of objects, which is what we often that resistance.We have experience in daily life, when you car at high speed out of the window on the handle when the role of resistance was felt.
resistance phenomenon and our production and life are closely related, have long attracted people's attention.However, the reasons for the resistance is very complex, it has been studied more than 2,000 years can not be said to fundamentally solve the problem.Establishment of the great scientists of the classical Newtonian mechanics system I had for many years.It was not until the 20th century, the development of the aviation industry and the needs of the people is rather clear understanding of this phenomenon.Resistance to many factors, such as the shape of the object, the fluid nature of movement speed, is difficult to give a unified explanation, different situations require different descriptions.
at high speeds, the resistance become critical, in order to study the air resistance, invented the wind tunnel.According to the principle of relativity, objects in motion in still air force conditions equivalent to stationary objects in the flow of the air force.Wind tunnel research stationary object is in the forces in the flow of equipment, people to create a fixed pipe flow can be controlled to simulate the movement of objects in the surrounding air flow, measured by sensors in the various shapes of objects suffered by the wind drag, lift, pressure and so on.Study currently in flight dynamics, wind tunnel experiments have played a decisive role.
real resistance
suffered in the fluid moving object can be roughly divided into the resistance of pressure drag and friction.As in the air, always in front of the movement of objects and arranged to squeeze the air pressure, formed in the rear wake zone, in the wake region of less pressure, which resulted in pressure drag; friction good understanding of the object and the interface between the fluid forms a boundary layer, relative movement between layers, friction is bound to exist.Further analysis of moving objects in the fluid resistance mainly from the molecular or atomic substances between the electromagnetic force, such as pressure from the object and the fluid molecules or atoms of the collision; friction mainly from the interface layer at different speeds between the molecular or atomic momentum exchange.
speed a great impact on resistance, generally faster, the greater the resistance, and speed should be proportional to n-th power, how much and n is the number of factors.Newton was considered proportional to the square resistance and speed, this is roughly consistent in some situations.In addition to speed, drag a great impact on the shape of objects in the same section and velocity case, the resistance of different shapes have very different sizes.In general, the formation of smaller wake region, resulting in resistance to small; steady laminar boundary layer flow of the turbulent boundary layer over the formation of vortex resistance.Wind tunnel tests and theoretical analysis have proved that streamline the shape of least resistance is to produce, which is widely used in high-speed streamlined case the reason.Under normal circumstances, the smoother the surface, the less prone to the boundary layer turbulence, friction on the small.But sometimes the surface is not smooth but will reduce the resistance, indicating that the resistance phenomenon is complex and can not be generalized.Ma Hang, such as golf full of golf than the smooth flight even further, because the rough surface boundary layer of air can be better attached to the sphere, the delay of the boundary layer separation with the ball, after the separation point shift to smaller wake region, increasing pressure wake region, making the pressure drag decreases; despite Ma Hang to the frictional resistance increased, but the overall resistance decreases.
in daily life, although in many cases we are doing everything possible to reduce the resistance, but no resistance is impossible, such as the sea can not do without resistance.If there is no resistance, I am afraid we have a problem of human existence, do not destroy the ground that meteor meteorite is a high-altitude rain will fall killed people, maybe people should wear water droplets.
sport of drag
in sports such as sprinting, skating, cycling, throwing the air resistance and other projects can not be ignored, swimming To overcome the resistance in both, but also the effective use of resistance to achieve better results.Especially in today, close to exercise extreme sports scores, the competition is more intense, athletic performance in the tenth of a second, hundredths of a second contest between the resistance effect becomes essential.
the bike race, the more obvious measures to reduce the resistance, the first bike racing is designed according to aerodynamics, ride a bike, the rider must lean forward, in line with the location of gas power in order to reduce resistance in the air.Cycling helmet-like shape of water droplets athletes head to replace the natural shape, so fast forward to minimize the eddy current effect, reducing the cycling of air resistance.Test showed that the air resistance to wear a helmet significantly less than the"shaved head" when the air resistance.
the density of water is much larger than air, in water resistance movement was greater.Swimming in it is necessary to do everything possible to reduce the resistance of the body forward, but also increase the resistance of the water in order to achieve good results.For example, people in bathing suits and down a great effort, recent experiments show that wearing a bathing suit appropriate resistance than swimming naked, and then people would not imitate the cortex to create a fake shark shark swimsuit, so swim increased.
ski jumping is a high-speed sports, and use reasonable overcome resistance, effect more visible.Early aerial ski jumping and snowboarding action as the body parallel to his arms out in front, arms and back was improved to try to be hip, to further reduce air resistance.At this point, the snow jump athlete's body has become a"vehicle", from the side looked exactly like an airplane wing profile.Snowboard air under the flat lower velocity in the head and shoulders high velocity uplift the human body back to form the upward lift.In 1985, Sweden's Jane Boca Rove pioneered the two parallel skis into a V shape, which is a"toe", so the flight distance increased by 10% and became the standard snow jump action.Although the opening of the air resistance is greater than ski skis parallel, but staggered as leakage of the ski area of the body to increase the flight, thus increasing the lift, so that the"lift-drag ratio" closer to a reasonable value.
