A riddle about scales
Balance (a mathematical term) (a comprehensive riddle)
Answer: Symmetry.
Hong Yan Qiu Shui and Tian Ping (playing an idiom)
Answer: The human eye is a measure.
Tian Ping said (to use an idiom)
Answer: Safe and sound.
Development history of balance
According to the records of papyrus, as early as 1500 BC, the Egyptians had already used the scale, and some people said that this time was even earlier, about 5000 BC. Although the scales in ancient Egypt were very rough, they already had the outline of modern scales and became the embryonic form of modern scales.
An ancient weighing instrument came into being relatively early. By the late Spring and Autumn Period, the manufacturing technology of balance and weight was quite sophisticated. Bamboo pieces are used as beams, silk threads are used as lifting buttons, and a copper plate is hung at each end. Later, it was more troublesome to weigh the weight with a scale. All? Use the balance only when weighing small things.
Composition of balance
Ordinary signboard scales are mainly composed of columns, beams, suspension systems, bases and braking devices.
The column is vertically fixed on the base to support the beam. The lower part of the column is equipped with an indexing disk, and the top is equipped with a bracket to support the beam when the balance is not working. A middle knife is installed in the middle of the beam. When the balance works, the middle knife rests on the knife bearing connected with the top end of the lifting rod as the fulcrum. There are two side knives on both sides of the middle knife, which are used as key points and stress points respectively to bear and transmit loads. The bottom surface of the lower beam of the middle knife is equipped with a pointer, and the center of gravity weight which can move up and down to adjust the center of gravity of the beam is fixed on the pointer, which plays a role in adjusting the sensitivity of the balance.
The top of the beam is engraved with a graduation scale, and the scale has a moving code. Balance nuts are also installed at both ends of the beam, which can adjust the no-load balance position of the balance.
The suspension system includes a small lifting ring, a hanging tray rack and a weighing pan. The hanging plate frame is hung on the hook of the small lifting ring, and the two side knives bear the weight of the weighing plate and the weighed object through the small lifting ring respectively.
Two screw adjusting feet are installed on the base to adjust the levelness of the balance, and a level meter is also installed on the base to display the levelness of the balance. The purpose of adjusting the level is to avoid the weighing error caused by uneven balance.
The braking device is mainly composed of switch knob, switch shaft and eccentric cam (or connecting rod). Turn the knob to deflect the cam (or eccentric connecting rod) by a certain angle, make the lifting rod in the column move up and down, make the beam rise or fall through the middle knife bearing, and open or close the balance.
Basic principle of balance
Balance is a commonly used instrument in laboratory. Balance is a weighing instrument, and it is also an instrument for measuring the mass of objects. It is made according to the lever principle. There are two small plates at both ends of the lever, one for putting heavy objects and the other for weighing objects. The center of the lever is equipped with a pointer. When the two ends are balanced, the masses (weights) of the two ends are equal. These truths are commonplace for people who have studied physics. Modern scales are more and more accurate, more sensitive and more and more kinds. As we all know, there are ordinary balance, analytical balance, constant analytical balance, micro analytical balance, semi-micro analytical balance and so on. It should be noted that the balance did not suddenly develop into what it is today, but it still has a history of development!
The invention of the balance was very early. In the Nile Delta of Egypt, there is an aquatic plant, which is very similar to the reed growing in our waters. Its stems are peeled off layer by layer and torn into thin slices for writing. This thing is called papyrus. Paper in many European countries evolved from Latin papyrus. Books written with papyrus are papyrus, which became an important historical document in ancient Egypt. Much of what we know about ancient Egypt today, especially the historical development of science and technology, comes from the records in papyrus. Of course, the cursive characters on paper are not modern characters, but hieroglyphics, which many experts have seen. According to the paper cursive script, as early as 1500 BC, Egyptians had already used scales, and some people said that this time was even earlier, about 5000 BC. Although the ancient Egyptian balance was very rough, it already had the outline of modern balance and became the embryonic form of modern balance. The picture below shows the scales used by the ancient Egyptians.
As can be seen from the picture, this balance is to drill a hole in the middle of a vertical stick, cross a stick and hang a plate at both ends of the stick with a rope. This kind of balance was used for a long time until it was built in Rome around 500 BC. A steelyard? Before it appeared, the lever weight kept the balance with the weight of the weighed object by moving the weight. In fact, it changes one end of the balance (the end where the weight is placed) from fixed to movable. Its advantage is that only one weight is needed, and the balance weight is better. The steelyard also hangs a plate with a rope and then hangs a weight with a rope. The basic form is the same as that of a balance except that one end can be moved.
In the use of scales and scales, people find it troublesome to hang plates with ropes and inconvenient to use. So, someone
Want to get rid of this nasty rope, in the middle of17th century, French mathematician Lauber Barr invented the swinging tray balance. The invention of pallet balance is considered as a great improvement on the ancient hanging balance, and it is still widely used today. The picture below shows an ordinary pallet scale in the laboratory, which is greatly improved compared with the pallet scale in17th century. 1 in the figure is a balance beam, and both ends support the weighing plate 2. These two parts constitute the skeleton of the pallet scale and embody the basic design principles of the pallet scale. See the following schematic diagram: when the beam 1 is balanced, the moments are equal, F 1L 1=F2L2, F 1=m 1g, F2=m2g, L 1 =. M 1gL 1=m2gL2, m 1=m2, that is to say, the mass of the weighed object can be known from the known weight.
It should be pointed out that the invention of pallet scale did not make the hanging scale withdraw from the historical stage. On the contrary, the hanging balance not only continues to be used by people, especially scientists, but also continues to be improved in use. The precision balance widely used in modern times is mostly suspended, while the pallet balance is more used in daily production and life, and more used in weighing with low precision requirements in scientific experiments.