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There's a good reason for the law enforcing seatbelt usage inmany states.
很多國家法律規(guī)定使用安全帶是有原因的。
Seatbelts saved nearly 12,000 lives in the year 2000.
2000年，安全帶的使用挽救了近1200條生命。
In this Moment of Science, we take a look inside thesesimple but highly useful machines.
讓我們通過科學(xué)一顆來了解一下這個簡單但又十分有用的裝置吧。
A seatbelt consists of a belt made of flexible webbing and a retractor device.
安全帶是由彈性帶和一個牽開器裝置構(gòu)成的。
The retractor, usuallylocated inside a plastic housing above the passenger's outer shoulder, consists of a spool aroundwhich the belt winds, and a spring attached to the spool to keep the webbing taut.
牽開器通常位于乘客外肩上方的塑料罩里，由一個纏繞彈性帶的線軸和一個依附在線軸上使彈性帶拉緊的彈簧構(gòu)成。
When you pull a seatbelt across your chest and pelvis, the spool spins counter-clockwise,untwisting the spring.
當(dāng)你拉開安全帶繞過你的胸和盆骨時，線軸就會逆時針旋轉(zhuǎn)，松開彈簧。
Since the spring wants to return to its coiled position, when you let go ofthe belt the spring causes the spool to spin clockwise, reeling in the slack.
當(dāng)你解開安全帶的時候，彈簧就會通過自身回力使線軸順時針旋轉(zhuǎn)，收緊安全帶。
The most important part of a seat belt is the spool's locking mechanism—a device that makes thebelt hold tight in the unfortunate event of a crash.
安全帶最重要的部分就是線軸的預(yù)收緊裝置，在發(fā)生車禍的時候可以使安全帶收緊，
The locking mechanism is activated either bythe car's movement or by the belt's movement.
汽車運動和安全帶運動都會觸發(fā)預(yù)收緊裝置。
In car-activated systems, when the car stops suddenly a weighted pendulum swings forward,causing a metal bar to jam into a toothed gear attached to the spool.
在汽車啟動觸發(fā)的情況下，汽車突然停下時，一個加重的擺錘會向前擺動，金屬棒就會卡進(jìn)依附在線軸的齒輪里。
Unable to unwind anyfurther, the belt holds the passenger tightly in place.
安全帶再無法被進(jìn)一步放開的情況下就會緊緊的將乘客束縛在座位上。
In belt-activated systems, centrifugal force, cause by a sudden jerking of the belt, causes a leverattached to the spool to move outward.
在安全帶激活系統(tǒng)中，由安全帶突然震動造成的離心力會使線軸上的杠桿向外移動。
The extended lever activates a device that catches thetoothed gear attached to the spool, stopping its spinning motion.
延長的杠桿會觸發(fā)線軸上與齒輪相連的一個裝置，從而使軸芯停止轉(zhuǎn)動。
In both systems, the point is totighten the belt so that its stopping power is spread across the sturdiest parts of your body.
這兩種情況的關(guān)鍵就是要收緊安全帶，這樣安全帶的收力才會傳遞到身體中最強壯的部分。
