時差N小時:利刃特別在何處 What's So Special About A Sharp Knife

Everyone knows that a sharp knife cuts better than adull one,but do you know why, exactly?

眾所周知，鋒利的刀刃的切割性遠(yuǎn)勝鈍刀，但你知道確切原因嗎?

The purpose of the cutting edge of a knife is toconcentrate the force that's being applied at thehandle.

刀刃的作用就是將人們用在刀把上的力集中起來。

When you push down on the handle of a knife youexert a force.

當(dāng)你按下刀把時，實(shí)際上你施加了一種力。

The force on the handle and the edge are the same, but the areas in which the force isconcentrated are quite different.

這種力無論是在刀把還是刀刃上都是等量的，但力的聚集區(qū)域不同，所產(chǎn)生的效果則有天壤之別。

At the handle your hand's force is spread over a wide area, but on the cutting edge itisconcentrated in a very small area, so therefore the pressure on the edge is much greater.

在刀把上，力會在一個較廣闊的區(qū)域傳播，但在刀刃上，力會聚集在一個非常小的區(qū)域，因此刀刃上的壓力會劇增。

You can easily see how this works with a piece of modeling clay, a nail with a wide head, and anail with a small head.

只要借助一塊橡皮泥、一枚寬頭釘和一枚窄頭釘，你很容易就能看到這一原理。

First hold the nail with the wide head by its shaft and push it head-first into theball of clay.

首先將寬頭釘?shù)臈U豎起，將其頭朝下推入橡皮泥球。

Then do the same with the small-headed nail.

然后對窄頭釘做同樣動作。

The small-headed nail goes into the clay much more easily than the wide-headed nail.

窄頭釘比寬頭釘更容易嵌入橡皮泥。

Since thehead of the small nail has less surface area than the big one, the force of your pushisconcentrated in a smaller area, exerts more pressure on the clay, and so the nail goes inmoreeasily.

由于窄頭釘?shù)念^部面積比寬頭釘小，你的推力將集中在一個更小的區(qū)域，對橡皮泥產(chǎn)生更大的壓力，因此釘子更容易嵌入。

The same principle causes pointed high-heeled shoes to sink into a soft surface moreeasilythan flat shoes.

同理，尖高跟鞋比平跟鞋更易陷入表面柔軟的物體。

By applying this principle to the knife you can see that with a keener edge there's agreaterconcentration of the pressure on the edge, so it takes much less force to make the knifecut.

將這一原理運(yùn)用在刀上，你能看到，在鋒利的刀刃上，壓力能更好的聚集，因此切割起來更省力。