The principle and characteristics of tape measure.

Principle:

The tape measure can be rolled up because there is a spring inside the tape measure. When pulling out to measure the length, the length of the scale and the spring is stretched. Once the measurement is completed, the spring inside the tape measure will automatically shrink, and the scale will follow under the action of the spring force. Shrink, so the tape measure rolls up.

Feature:

1. The tape measure will not fail if it is deformed too much. Why did it not fail? The mainspring in the tape measure is very long, and it has a wide range from fully relaxed to fully tightened. The entire stroke of the tape measure includes it, with a margin at both ends, so the tape measure does not fail.

2. There is no difference in pulling force between a one-metre and a two-metre length. the spring of the tape measure is very thin, and the deformation is also small when tightened, so the reaction force is very small, and the force change cannot be felt when pulling the ruler.