【英语时差8,16】你的快速球投的如何？

 Pop quiz: You have a flat table and two billiard balls. You and your strong-armed friend each roll one of the balls off the table so they pass the edge at the same time, only his ball is traveling much faster than yours. Which one hits the ground first?

 

It's one of the perennial¹ stumpers of physics class that, provided they both pass over the edge simultaneously², both balls will land at exactly the same time. In fact, no matter HOW fast the "fast" ball is moving, it will still fall at the same speed as the ball that just meanders³ over the edge. Yes, even if the "fast" ball is fired out of a cannon⁴, this will still hold true. The reason is that horizontal motion in no way affects vertical⁵ motion: gravity acts on both the fast ball and the slow ball with the same force at all times. So while the fast ball lands much farther away, it doesn't get to spend any more time in the air than the slow ball -- or, for that matter, than any other ball moving at any speed in between.

 

In fact, the only thing that will make a difference in the landing times of the two balls is the curvature of the earth. If the fast ball moves SO fast that it's able to get past the point where the ground starts to drop away significantly underneath⁶ it, it then will indeed spend a longer time falling, but only because it will now have a greater distance to fall. And if you can generate the kind of energy required to produce this effect, you have just succeeded in putting your fast ball into orbit.  

1 perennial   

adj.终年的；长久的

参考例句：

• I wonder at her perennial youthfulness.我对她青春常驻感到惊讶。
• There's a perennial shortage of teachers with science qualifications.有理科教学资格的老师一直都很短缺。

2 simultaneously   

adv.同时发生地，同时进行地

参考例句：

• The radar beam can track a number of targets almost simultaneously.雷达波几乎可以同时追着多个目标。
• The Windows allow a computer user to execute multiple programs simultaneously.Windows允许计算机用户同时运行多个程序。

3 meanders   

曲径( meander的名词复数 )； 迂回曲折的旅程

参考例句：

• The stream meanders slowly down to the sea. 这条小河弯弯曲曲缓慢地流向大海。
• A brook meanders through the meadow. 一条小溪从草地中蜿蜒流过。

4 cannon   

n.大炮，火炮；飞机上的机关炮

参考例句：

• The soldiers fired the cannon.士兵们开炮。
• The cannon thundered in the hills.大炮在山间轰鸣。

5 vertical   

adj.垂直的，顶点的，纵向的；n.垂直物，垂直的位置

参考例句：

• The northern side of the mountain is almost vertical.这座山的北坡几乎是垂直的。
• Vertical air motions are not measured by this system.垂直气流的运动不用这种系统来测量。

6 underneath   

adj.在...下面，在...底下；adv.在下面

参考例句：

• Working underneath the car is always a messy job.在汽车底下工作是件脏活。
• She wore a coat with a dress underneath.她穿着一件大衣，里面套着一条连衣裙。