Why do sharp things cut

Some of the little jaggies will break off even when cutting soft objects. The knife is impelled by kenetic energy. So the cheese gives way. Mainly, I think you are just pushing the tiny little molecules aside.

Cutting a polymer is a different story. In that case the stresses are breaking molecular bonds, but it is still not accurate to think of it as a blade slicing through the bonds, because on a molecular scale, the blade is as sharp as a hammer. Mostly I think the jagged edges are catching molecules and pulling them apart. What is interesting to consider, is whether the bonds are broken homolyticly or heterolyticly. Analysis of the products would easily distinguish the two, if somebody thought it worthwhile to find out.

That is, the bond strength decreases as you increase the distance between the atoms. It seems to me that the force required will depend on the materials and shape of the cutting implement and of the object that is being cut. And, that some of the variables would be the hardness, ductility, elasticity, tensile strength, brittleness, and crystallinity and, possibly, melting point of those materials.

But, in some cases, it seems that the motion across is not necessary, eg. But, is shear stress always a component of cutting? Look, at the atomic level, we have some atoms, and they are all bound together to make a molecule. And that molecule happens to be next to another, relatively identical molecule. And something holds those two molecules together, so that they react to forces applied by staying next to each other. WHY are they pushing the molecules apart?

So far, no one has offered an explanation at the appropriate level. I think this has been covered. Force is applied by the repulsion of the electrons in the molecules. The blade of a knife is like a very thin hand.

It applies huge pressure at the edge to push the material apart. When you try to cut a tomato, a blunt knife crushes a wide band of plant cells underneath it but a sharp knife will cut through a single line of cells, separating the long-chain cellulose molecules in the cell wall.

The sharpest knives are those with the thinnest edges. Another thing is the shape of the blade, that is also the reason why we do not chop wood with kitchen knives and vice versa. Rapiers are good at fast stabbing, whereas lacking strength and cutting ability.

On the other hand, khopesh or machete are great for cutting. Saw or bread knife represent another example- they have serrated blade and thus are great at cutting soft or fibrous material wood, bread.

I am really no expert in blades or physics, but yeah this makes sense, right? Hope you did all learn something new today. I did get a bit out of my biological comfort zone, so hopefully I said everything as it is and will not be pursued by physics-hunters. Blade — Wikipedia article And my own knowledge and experience..

Guidelines Project Update. All posts. Newcomers' Community. Steemit Feedback. Explore communities…. What makes an object sharp? Physics of Sharpness. Source What is sharpness? Source Well, first of all butter knife and kitchen knife are different. Here we get to basic physics: The p stands for pressure, F for force and A for area. Is there more to it? Stay sharp! References Blade — Wikipedia article And my own knowledge and experience.. Reply 3. Sort: Trending Trending Votes Age.

That might be a good choice of weapon :D.