Speed

Speed. Written by Bruce D. Cooper.

《速度》 作者：布鲁斯·D·库珀

Introduction. What is speed? Speed is the time it takes to go a certain distance. For most things, speed is measured in kilometers or miles per hour. For example, a speed of 16 kilometers, 10 miles per hour, means that something is moving fast enough to travel 16 kilometers in one hour. This speed is recorded as 16 kph, 10 mph. Speed can also be measured in other units of time and distance. It can be measured in meters per second or meters per minute. It can be measured in centimeters or inches per second,

引言 什么是速度？ 速度就是物体走过一段特定距离所用的时间。 大多数物体的速度，单位是千米每小时或英里每小时。 比如速度16千米（10英里）每小时，意思就是物体一小时可以走完16千米。 这个速度记作16kph（10mph）。 速度也可以用其他时间、距离单位计量。 可以用米每秒或是米每分钟做单位。 也可以用厘米每秒或是英寸每秒。

Faster objects are usually measured in larger units of distance and shorter units of time. Slower things, on the other hand, are usually measured in smaller units of distance and larger units of time. For example, a snail's speed might be measured in centimeters per hour. The movement of a glacier might be measured in meters per month. Light, the fastest thing in the universe, moves at 299 ,338 km per second, 186 ,000 miles per second.

速度越快的物体，通常用更大的距离单位、更短的时间单位计量。 反过来，速度越慢的物体，通常用更小的距离单位、更长的时间单位计量。 比如说，蜗牛的速度就可以用厘米每小时计量。 冰川移动的速度可以用米每月计量。 宇宙中最快的光，速度是每秒299338千米，即每秒186000英里。

People have always seemed to be fascinated by speed. We seem to love things that move fast. It doesn't matter if it is a cheetah chasing a gazelle, a horse galloping around a track, or human runners dashing toward a finish line. We simply think that fast things are cool. Perhaps that is why some of the most popular Olympic events from the first games on have been contests involving speed.

人类一直都对速度着迷。 我们天生喜欢速度快的事物。 不管是猎豹追捕瞪羚、赛道上马儿奔跑，还是赛跑选手冲向终点，我们都看得津津有味。 我们就是觉得速度快的东西很酷。 也许这就是为什么，从第一届奥运会开始，最受欢迎的项目里总有比拼速度的赛事。

Who is fastest? When we watch a track meet or other sporting event, we cheer for the fastest runners. But compared with other living things, humans are not all that fast. In fact, the fastest humans run at speeds of only about 35 .4 kilometers per hour, 22 miles per hour.

谁跑得最快？ 我们看田径赛或其他体育赛事时，总会为跑得最快的选手欢呼。 但和其他生物比起来，人类其实不算快。 实际上，跑得最快的人类，时速也只有大约35.4千米，也就是22英里每小时。

Speed is important for the survival of most living things. The cheetah, which runs at speeds of up to 113 kilometers per hour, 70 miles per hour, is the fastest living thing on land. The cheetah depends on its speed to capture food. For many animals, survival often depends on being faster than the animal that is chasing you.

对大多数生物来说，速度关乎生存。 陆地上跑得最快的生物是猎豹，它的时速能达到113千米，也就是70英里每小时。 猎豹靠速度捕猎获取食物。 对很多动物来说，活下去的关键，就是比追你的捕猎者跑得更快。