英语听力文摘 English Digest 528、为何高尔夫球上有小窝？

 　　Why Do Golf Balls Have Dimples?

 

　　You’re out on the golf course one pleasant afternoon. Your ball is set on the tee. You lean over the ball. You grip the club just right.

 

　　Your arms are straight. Your stance perfect. Whoosh¹! You swing, and the ball takes off toward the green, sailing in a beautiful arc–almost as if it’s weightless.

 

　　Your impeccable technique certainly has a lot to do with the success of that drive, but you got a major assist from the little dimples on the golf ball–and they’re the subject of this Moment of Science.

 

　　Combined with the proper spin, the dimples help keep the ball in the air longer, and here’s how.

 

　　Your picture-perfect swing puts backspin on the ball. The dimples trap a layer of air next to the ball, and this layer spins with the ball.

 

　　The air being dragged across the top of the spinning ball moves in the same direction as the air that’s rushing past. As the air spinning with the ball comes around the bottom it is moving in the opposite direction from the air on top, and therefore against the onrushing air. Consequently it’s slower than the air on top.

 

　　A slow moving air stream has higher pressure than a fast moving air stream. So, the higher pressure on the bottom of the ball is going to hold the ball up longer.

 

　　The effect of the dimples is so significant that a drive of two-hundred yards hit with a dimpled golf ball, would be shortened² with a non-dimpled ball to about one hundred yards.

1 whoosh   

v.飞快地移动，呼

参考例句：

• It goes whoosh up and whoosh down.它呼一下上来了，呼一下又下去了。
• Whoosh!The straw house falls down.呼！稻草房子倒了。

2 shortened   

v.弄短，缩短( shorten的过去式和过去分词 )

参考例句：

• She shortened the skirt by an inch. 她把裙子缩短了一英寸。 来自《简明英汉词典》
• Vacations have lengthened and the work week has shortened. 假期延长，工作周就缩短了。 来自辞典例句