【英语时差8,16】空中舞蹈2

（单词翻译）

 A skydiver’s body is in a delicate balance. Gravity tugs¹ her downward with a constant, relentless² force, while air resistance pushes her upward. The faster she falls, the more air resistance there is, so eventually these two forces cancel out. Then she falls at a constant rate, her terminal velocity³. To link up with other skydivers in mid-air formations, skydivers need to control their terminal velocity very carefully. After all, if you’re falling at a hundred and ten miles per hour, and your friend is falling at a hundred and twenty, there’s no way you can link at all. As it turns out, your terminal velocity is determined⁴ by exactly two things–your weight, and the amount of surface area you expose to the ground. While a skydiver can’t do anything about her weight mid-fall, she can control how much area she presents downward. Stomach down, with arms and legs spread out in a kind of belly-flop, the average skydiver is likely to fall at around a hundred and ten miles per hour.