Learning "Understanding of Clock" in the second grade of primary school mathematics is both important and difficult. The teaching content of this lesson is mainly to guide students to know, read and write the whole time in observation and comparison, to feel the connection with life in the process of learning mathematics, to guide students to feel the preciousness of time and to educate students to cherish time.

Clocks and watches:

The clock is a timing device and a precise instrument for measuring and indicating time. Clocks are usually distinguished by the size of the internal machine.

According to international practice, clocks and watches with a movement diameter greater than 80 mm and a thickness greater than 30 mm; A pocket watch with a diameter of 37 ~ 50 mm and a thickness of 4 ~ 6 mm is called a pocket watch; Watches with a diameter less than 37 mm; A watch whose diameter does not exceed 20mm or whose movement area does not exceed 3 14m2 is called a women's watch. The watch is one of the smallest, strongest and most sophisticated machines invented by human beings.

Clocks and watches have always been one of the favorite commodities of Chinese people. Since the founding of New China, the state has invested a lot of money to develop the watch industry, which has made the industry develop rapidly. Since then, China's reform and opening up and economic globalization have brought prosperity to China's watch industry.

After decades of development, China watch industry has experienced the process of material assembly-appearance parts manufacturing-product development-brand creation. At present, a complete watch manufacturing industry has been formed, and spare parts except high-end movements can be processed and produced.

Refer to the above? Baidu encyclopedia-clocks and watches