It has been reported that
The closing ceremony was held at the Chengdu Open Air Music Park. It is the first time in the world that the closing ceremony of a large international sporting event
China
2 . In the Beijing Winter Olympics, we were treated to incredible displays of athletic talents ascompetitors took to the snow and ice. As a popular sport at the Winter Olympics, ski jumping is oneof the best examples to showcase the “superhuman” power of athletes.
Ski jumpers soar into the air and appear to be almost flying in the sky. How do they achieve this? Physics call offer us an explanation of how they make it. It involves the use of the laws of aerodynamics(空气动力学)to fight against gravity and increase lift while reducing drag.
To understand how ski jumping works, we need to consider three elements: gravity, lift and drag. Gravity is the force that pulls us towards an object. Lift occurs when an object is moving through the air—as its surface comes into contact with air particles(微粒), the particles are pushed down and away from the object, allowing it to move up. At the same time, this interaction createsdrag, and slows down an object’s movement.
While there is nothing that the skiers can do about gravity, they can twist their bodies into positions to allow them to achieve greater lift and avoid as much drag as possible. According to the Smithsonian Magazine, “To do this, athletes try their best to make their skis and body nearly parallel to the ground and place their skis in a V-shape just outside the form of the body. This position increases the surface area that produces lift and puts them in the ideal angle that will also maximize(最大化)lift.”
Because of how the sport works, athletes’ equipment is strictly controlled according to weight and height in order to avoid any unfair advantages. This means suits must be tight in order to ensure athletes cannot use them as a way to gain more lift. For athletes, minor day-to-day waterweight changes as little as 300 grams. It can mean that suits will not be tight enough according to their body mass indexes(体重指数).
1. What does the underlined word “It” refer to in the second paragraph?| A．Athletic talent. | B．Ski jumping. |
| C．Physical science. | D．Superhuman power. |
| A．The interaction between force and drag. |
| B．The interaction between gravity and balance. |
| C．The interaction between skiers and air particles. |
| D．The interaction between air particles and gravity. |
| A．Standardized equipment. | B．Specially made suits. |
| C．Strict control of athletes’ height. | D．Much daily water intake. |
| A．The techniques used by ski jumpers. |
| B．Rules of the ski jumping competition. |
| C．Excellent performances in ski jumping. |
| D．The scientific principles behind ski jumping. |
Square dancing has become more and more popular in recent times, especially for the middle-aged women. Square dancing is not
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