- Nov 22, 2017 -
You noticed scissors for different uses, their shape is different? For example, the scissors that the hairdresser used to cut his head had a short scissors handle, but the length of the scissors was quite long. The scissors that the gardener used to cut the branches were exactly the same as the scissors in the barber's hand, Knife is short; as we usually use the scissors, scissors handle and scissors mouth, often about the same length.
Why the shape of the scissors is not the same? To clarify this principle, we must first talk about the labor-saving role of leverage.
When people move heavy objects on the ground, they often use an iron bar to pry, put one end of the bar under the weight, put another piece of wood or something under the bar, and then forcefully press down at the other end The weight was lifted up by the iron rod. Here, the iron bar is the lever. There are three main points on the iron bar: it rests on a point called a fulcrum on a piece of wood, a point that is held by a human hand is a point of force, and a point inserted under a heavy object is the point of focus. The distance between the fulcrum and the force point is called the arm, the distance between the fulcrum and the focus is called the boom.
According to the lever balance principle is: force × arm = weight × boom.
From this principle we know that the longer the arm, the shorter the arm, the more effort. For example, put the iron rod arm arm length of 3 meters, arm length of 0.3 meters, then as long as 10 kilograms of force, you can lift 100 kilograms of heavy objects.
Scissors and iron bars appear to be two different things, but they are exactly the same in terms of leverage. The scissors also have a fulcrum, that is, the iron core that connects the two halves of the scissors together, and there is also a point that the scissors's mouth cuts at the point of the object; its force point is that the scissors handle is hard and the scissors's mouth is closed. opened.
Horticultural workers cut branches of the scissors, because the branches harder, it takes a lot of effort to cut, so it's handle to do a long, so that the force point away from the fulcrum far, cut the branches, it is very effort; then Barber accepted the scissors, scissors length, scissors handle short, it is to be more effort? No, this is because the hair is delicate and easy to cut, do not have to use great efforts to make scissors mouth long, a pair of scissors can cut more hair, can improve work efficiency. As we usually use the scissors, because to consider a variety of purposes, so the scissors and scissors handle length often do almost.