How Knives Work

Have you ever wondered how a knife works? How is it that a machine as simple as a blade of metal is able to accomplish things so elegantly that we could only do with brute force?

Take, for example, a steak knife. If you want to eat a steak, you have the option of picking it up in your fingers and ripping off bite-size pieces to put in your mouth. But isn’t it much more neat and convenient to have a knife neatly slice through the meat, giving it a clean edge and a perfectly sized piece? How does it do that?

Everybody knows that a knife is better when it’s “sharp”. What does “sharp” mean? It means that the edge comes to a definite point instead being rounded.

Consider it this way. When you push down on a knife, you exert force through the knife onto the piece of meat. Let’s say that’s a force of, oh, five pounds or so. But it’s not just five pounds. That force is spread over the surface area of the meat where the knife meets it.

Hang in there. We’re getting close to understanding how this works.

Suppose you lay the knife on its side and push down. That five pounds of force is now spread over the surface of the knife blade — perhaps two or three square inches. Not much cutting power there, huh? Just a mushed-up piece of meat.

Now turn the knife on its sharp edge. Push down with the same force. That same five pounds of force is still being exerted on the meat. But instead of being spread over two or three square inches, the force is concentrated. Let’s see — how much area do you think is represented by the edge  of the knife as opposed to the side?   Infinitesimal, don’t you think? And the sharper the knife is, the less surface area is represented by the edge and the more concentrated the force is.

Knives work not because they are strong, but because they concentrate all their strength in a very small area.

There’s a lesson to be learned from this. When we are in a struggle, it often isn’t important how strong we are — individually or collectively. What really makes us effective is when all our strength is concentrated in a small area. The greater the concentration, the more effective our relative strength.

“Sharpening” our skills doesn’t refer to making us stronger, smarter, or better. It means learning how to effectively utilize the skills that we already have — concentrating them in a small area — to get the job done.