The reason why the tape measure can be rolled up is that there is a spring inside the tape measure. When pulling out the measuring length, the length of the ruler and the spring are actually stretched. Once the measurement is completed, the spring inside the tape measure will automatically contract, and the ruler will also contract under the action of the spring force, so the tape measure will be rolled up.
One, the tape measure deformation is too big will not fail. Why didn't it fail; The spring in the tape measure is very long, and its complete relaxation to complete contraction interval is very large. The whole travel of the tape measure includes it, leaving a margin at both ends, so the tape measure will not fail.
Two, pull one meter long and pull two meters long, pull no difference; The spring of the tape measure is very thin, the deformation is also very small when tightening, so the reaction force is very small, when pulling the tape, you will not feel the change of force.
A tape measure has the same scale as a tape measure in metric system. A centimeter of a tape measure is the same as a centimeter of a tape measure, except for a blind tape measure used by black-lined clothing merchants.
The reverse side of the tape measure is the city scale: the city scale, the city inch; The front side of the tape measure is divided into two parts, with a metric scale (meter, centimeter) on one side and a British scale (foot, inch) on the other.
Numbers on the tape measure:
Figures on the tape is divided into two rows, row number unit is CM/CM, a row of the unit is inch, 1 CM = 0.3937 inches, about about 1 inch = 2.54 CM, so the two Numbers separated by short digital unit is CM, longer for inch, the number of units CM font is smaller than inches, 100 CM = 1 m, use in general use unit is CM.