The tape measure can be rolled up because there is a spring inside the tape measure. When the measuring length is pulled out, the length of the ruler and the spring is actually stretched. Once the measurement is completed, the spring inside the tape measure will automatically contract, and the ruler will follow the action of the spring force. Shrink, so the tape will roll up.
1. Features of tape measure
Gift rulers are used for advertising and promotion. They are divided into steel tape (steel tape) and leather tape (PVC plastic fiber tape). They are usually cute and compact. Tape measures are also called measuring tools. Eighty-five percent of the world's tape measures are exported from China.
　　2, the characteristics of the tape measure
(1) The tape measure is too deformed and will not fail
　　 Why didn't it fail? The spring in the tape measure is very long, and its range from completely relaxed to fully tightened is very large. The entire stroke of the tape measure includes it, and there is a margin at both ends, so the tape measure will not fail.
(2) Pull one meter long and pull two meters long, there is no difference in tension
        The spring of the tape measure is very thin, and the amount of deformation when it is tightened is also small, so the reaction force is very small, and the force change is not felt when the rule is pulled.