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Why does a newspaper tear smoothly up and down but not side to side?
[ 2006-08-11 11:08 ]
不知道大家有沒有注意過一個奇怪的現象：報紙若是豎著撕，就能直直地撕開；若是橫著撕，總是撕偏了、撕個扇形下來。這究竟是為什么呢？看了下面這篇短文，你就知道了。
 Newspaper is made up of tiny wood fibers. If you take a close look with a magnifying glass, you'll see that the fibers all line up in the same direction, up and down on the page. This gives the sheet of newspaper agrain.
When you tear the newspaper from top to bottom it tears evenly because you are tearing in the direction of the grain. But when you tear it from side to side, it tears unevenly because you're tearing against the grain.
grain: 紋理（木頭的纖維組織的排列、方向或圖案）
（英語點津 Annabel 編輯）
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