英语听力文摘 English Digest 215、会“溜”的悠悠球

　　What Makes a Yo-Yo Yo
悠悠球(YO-YO) 并非一个令人陌生的词眼，史书的最早记录出现在公元500年前的希腊;相传16世纪，菲律宾的狩猎民族在狩猎和格斗使用的器具中，在绳子的前端挂着重物似悠悠的武器，据悉这是悠悠的起源。大约300年前，悠悠传到了日本，被形象地叫作“独轮车”或“钱轮”，深受年轻人的欢迎。18世纪初叶，悠悠在英国以“王子财宝”、在法国以“诺尔曼悠悠”之名广为流行，尤其是在法国和英国的上流社会盛行。此后，这种玩具和“悠悠”的名字从法国流传到世界各地。因为每个球手的风格和自创花式都不尽相同，所以悠悠球的技术花式种类非常繁多，可以说是一个技术的海洋。目前主流的五个花式组别，每个组别的花式种类都数以千计，而且每年仍然会有非常多的新花式被研究出来。

　　Ever wonder what makes a yo-yo yo?
Why do yo-yos come back up again?That's a good question,look! And the answer lies in physics. You may have heard the term “inertia¹(惯性)”. Inertia is the tendency of something in motion to stay in motion, and something at rest to stay at rest. When you let go of the yo-yo, gravity causes it to start moving down.
Now, because it has a string wrapped around its axle（车轴）, the yo-yo will start spinning. By the time it reaches the end of the string, it is spinning fast. And because of inertia, it has a strong tendency to keep spinning.
The string that holds the yo-yo is attached to the axle in its middle. As the string unwinds（卷回）, that axle is spinning too. So when it runs out of string, the axle keeps on spinning, causing the string to wrap itself around the other way. That’s how the yo-yo winds（缠绕） itself back up.
Now in most yo-yos, there’s a small loop（环） at the bottom of the string. The yo-yo can be made to hang in that loop momentarily; that’s called “sleeping” the yo-yo. A quick tug（猛拉）on the string pulls the loop against the axle, increasing the friction²（摩擦力） between them.
That momentary³ increase of friction causes the string to catch on（抓牢） the axle, wrap around the spinning axle, and up comes the yo-yo again.
注释：
catch on
1.抓牢
The girl kept catching⁴ on to her mother's skirt.
小女孩一直紧紧地拉着妈妈的裙子。
2.理解
I don't quite catch on to what she is saying.
我不太明白她在说些什么。
3.流行
It is a nice song and I think it will catch on quickly.
这首歌很好,我想它会很快流行。

1 inertia   

adj.惰性，惯性，懒惰，迟钝

参考例句：

• We had a feeling of inertia in the afternoon.下午我们感觉很懒。
• Inertia carried the plane onto the ground.飞机靠惯性着陆。

2 friction   

n.摩擦，摩擦力

参考例句：

• When Joan returned to work,the friction between them increased.琼回来工作后，他们之间的摩擦加剧了。
• Friction acts on moving bodies and brings them to a stop.摩擦力作用于运动着的物体，并使其停止。

3 momentary   

adj.片刻的，瞬息的；短暂的

参考例句：

• We are in momentary expectation of the arrival of you.我们无时无刻不在盼望你的到来。
• I caught a momentary glimpse of them.我瞥了他们一眼。

4 catching   

adj.易传染的，有魅力的，迷人的，接住

参考例句：

• There are those who think eczema is catching.有人就是认为湿疹会传染。
• Enthusiasm is very catching.热情非常富有感染力。