What are the principles and characteristics of tape measures?
Principle
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.
Feature
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 it is completely relaxed to completely tighten the range. The entire stroke of the tape measure includes it, and there is margin at both ends, so the tape measure will not fail.
Second, there is no difference in tension between a one-meter length and a two-meter length; the spring of the tape measure is very thin, and the amount of deformation when tightening is very small, so the reaction force is very small, and no force change is felt when the rule is pulled.