Pulling one meter long and pulling two meters long, the tension is no different; the spring of the tape measure is very thin, and the amount of deformation when tightening is also small, so the reaction force is small, and the force change is not felt when the ruler is pulled.
The "core" of the tape measure has a small piece of steel inside, which acts like a spring. It can also be thought of, that is, the one above the toy pistol trigger, which is used to "blow" the bullet with the small wire. When it is pulled out, it is forced to bend, and the external force is released (refer to the force of the hand, and the friction is more Small, less than the elastic force of the small wire) disappears, so it automatically bounces back. The front part of the tape measure has a folded part, which works at this point, so that the tape measure is stuck outside so that it does not completely retract. At first he was loose. When he pulled it out, he became tight. After releasing it, it should have a recovery process, so it will automatically bounce back. It was that he was loose at the beginning, and it was tight when he pulled it. There was a stretch between them. When he released it, he would bounce back.