【英语时差8,16】跳伞的科学依据（上）

 Why would you want to jump out of a perfectly¹ good airplane? Well, you get to the ground much faster, and the trip down is a whole lot more interesting. Skydiving has become an increasingly popular sport, although most of us haven’t yet taken the plunge² and only enjoy it from the sidelines. If you’ve seen video of skydivers in action, especially skydiving teams that link up to create formations, you might wonder how they do it. It’s a matter of elementary physics. Any falling object experiences basically two forces: The downward tug³ of gravity, and the upward push of air resistance. When a skydiver first leaps out of a plane, she begins accelerating rapidly downward, tugged⁴ down by gravity. If you or I fell out of a tree, we would experience the same thing–this is the usual experience of falling. After about ten seconds though, she stops accelerating downward. She’s still falling of course, usually at around a hundred and fifteen to a hundred and thirty miles per hour, but her downward speed is no longer increasing.

1 perfectly   

adv.完美地，无可非议地，彻底地

参考例句：

• The witnesses were each perfectly certain of what they said.证人们个个对自己所说的话十分肯定。
• Everything that we're doing is all perfectly above board.我们做的每件事情都是光明正大的。

2 plunge   

v.跳入，(使)投入，(使)陷入；猛冲

参考例句：

• Test pool's water temperature before you plunge in.在你跳入之前你应该测试水温。
• That would plunge them in the broil of the two countries.那将会使他们陷入这两国的争斗之中。

3 tug   

v.用力拖(或拉)；苦干；n.拖；苦干；拖船

参考例句：

• We need to tug the car round to the front.我们需要把那辆车拉到前面。
• The tug is towing three barges.那只拖船正拖着三只驳船。

4 tugged   

v.用力拉，使劲拉，猛扯( tug的过去式和过去分词 )

参考例句：

• She tugged at his sleeve to get his attention. 她拽了拽他的袖子引起他的注意。
• A wry smile tugged at the corner of his mouth. 他的嘴角带一丝苦笑。 来自《简明英汉词典》