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Published on Taipei Times http://www.taipeitimes.com/News/lang/archives/2007/09/30/2003381288 Sunday Science: Newton's law of inertia 週日科學:牛頓慣性定律 Sunday, Sep 30, 2007,Page 14 Do you always wear your seat belt when you are traveling in moving vehicles? This week's experiment will use physics to find out why seatbelts are a good idea. You'll need to find a safe place outside with a smooth surface and a wall. You'll be crouched down a lot for this experiment, so make sure you're away from traffic. What you will need: A box of eggs A toy truck (big enough to hold an egg) or a small Tupperware box. Some markers (optional) Anything from around the house you think might act as a cushion, for example, bubble wrap, tissue paper, a dishcloth, a sponge, cotton puffs. Sticky tape Elastic bands ► First of all you can decorate your eggs. Use the marker to give each egg its own face and personality. ► Using a section cut from the egg box (or some modeling clay if you brought loose eggs), make a seat for the egg in your vehicle. ► Take your truck outside. Don't put an egg in it yet. ► First experiment pushing and stopping the truck using the wall or your hands. How can you make the truck go? Does it go in a straight line? How can you make it stop? ► Now place your first egg passenger in the seat. Push the car hard towards the wall. What happens to the passenger? ► Retrieve the truck. Try to make the truck safer by using a material such as bubble wrap to cushion the egg passenger. Then push the truck into the wall again. ►Retrieve the truck. Using elastic bands or sticky tape try to make a seat belt for your next egg passenger. Then push the truck into the wall again. What happens? ► If your egg passengers are still getting hurt, keep trying to design an effective seat belt, until you can safely crash your truck and keep your eggs safe. (Catherine Thomas, staff writer) 你坐在行進車輛中會繫緊安全帶嗎？本週的實驗將利用物理原理來發現安全帶的好處。你需要到外面找個表面平坦且有一道牆的安全地點。進行這個實驗，你得不斷彎下身來，所以務必遠離車流。 所需材料︰ 一盒雞蛋． 一輛玩具卡車（要大到能裝進雞蛋）或一個小的特百惠餐盒， 一些馬克筆（可有可無）， 家中任何可充當緩衝墊的物品，如：泡泡棉、衛生紙、桌巾、海綿、化妝棉 膠帶， 橡皮筋 ► 首先，裝飾一下雞蛋。用馬克筆幫每顆蛋畫上代表自己個性的臉譜。 ► 剪下一小段蛋盒（如果你拿的是散裝雞蛋就利用一些黏土），做為雞蛋在玩具車內的座位。 ► 把玩具卡車拿到外面。先別把蛋放進去。 ► 首先，試著推動玩具卡車，再利用牆面或自己的手擋下車子。你要怎麼讓卡車移動？卡車的動線呈一直線嗎？你要怎麼讓它停下來？ ► 現在把第一位雞蛋乘客放到座位上，並把卡車朝牆面用力推去。雞蛋乘客會怎麼樣？ ► 取回卡車。用泡泡棉將雞蛋乘客包裹起來，讓卡車更安全。接著，再把卡車推向牆面。 ► 取回卡車。利用橡皮筋或膠帶替下一位雞蛋乘客做一條安全帶。再一次把卡車推向牆面。結果又會如何？ ► 如果雞蛋乘客還是受傷了，就繼續設計有效的安全帶，直到能安全進行卡車撞擊，並保護雞蛋乘客毫無損傷
Science Journal 科學日誌 Have you ever been in a car that had to stop suddenly? What happened to the people and objects in the car? Were they secured? How do you think it would make a difference? 你遇過必須緊急煞車的情況嗎？車內的人或物品怎麼樣了？他／它們有被安全固定嗎？你覺得怎麼樣才會出現不同的結果？ What's the science? 科學原理 This demonstrates Newton's first law, sometimes called the law of inertia. The law states: ↗An object tends to stay at rest until a force causes it to move.∫ When you push the car, your push is a force, which makes it move. The law further states: ↗an object which is moving tends to keep moving until a force causes it to stop.∫ When the truck hits the wall, the wall exerts a force on it, which causes it to stop. When your truck has an egg passenger, the egg passenger is moving at the same speed as the truck. The wall stops the truck, but not the egg. If the egg is not secured to the truck, the egg will keep moving at the same speed until something applies a force which will make it stop. Splat! Once the egg is secured to the truck, when the truck hits the wall, the seat belt will exert a force on the egg to keep it safely in place.
這印證了牛頓第一定律，有時也稱為慣性定律。慣性定律的第一部分說：「除非物體受到外力，迫使它改變運動狀態，否則靜者恆靜。」推動玩具卡車時，你的推力就是讓卡車改變靜止狀態的外力。慣性定律的第二部分則是「除非物體受到外力，迫使它改變運動狀態，否則動者恆動」。當玩具卡車撞上牆面時，牆面對車子所施加的作用力讓車停止。當卡車載了雞蛋乘客，雞蛋乘客便以和卡車等速的速度運動。牆面讓卡車停止行進，但雞蛋則不然。如果雞蛋沒有固定在卡車上，那麼在受到外力阻擋前，雞蛋仍會以等速向前運動。啪嗒！一旦雞蛋固定在卡車上，當卡車撞擊牆面時，安全帶就會施加作用力在雞蛋上，讓它保持在安全的位置。
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