What does the tick mark on the yellow calendar mean?

This is the design of ninth grade physics teaching in Luannan County, and it is also used for reference by many physics teachers or books.

Its purpose is actually to verify that both the spring tensiometer and the hair can produce elastic force, and the elastic force is limited. When the elastic limit of the material is exceeded, the material will break. Read the tension when the hair breaks, which is the maximum tension that the hair can bear, that is, the limit of hair elasticity.

In colleges and universities and some scientific research institutes, the process of tensile test of some materials with tensile testing machine is similar, that is, the sample is clamped on the machine, and the tensile force is gradually increased, and the ultimate tensile force is given at the moment of fracture.