Why is it that when you cut a small part of plastic it makes tearing much easier?
In: 17
ELI5: Let’s say you have a sheet of plastic and you begin stretching it from the sides, notice how the entire sheet stretches length wise almost evenly, now if you start again on a new sheet but with a cut on it’s side you’ve effectively decreased the length of the part you’re stretching from the size of the sheet to the size of the cut, since there is less material to resist the forces it tears across the entire thing.
Bonus: The cool thing is, you can prevent a cut from tearing by punching it with a hole-puncher because this restores some of its length and this is done to prevent tears in e.g, metal girders using drills or hole-saws (circle shaped saws for drills) to literally just drill out the cracks and refill them after.
Here’s a couple videos about metal crack repair that show how it’s done:
[Engine Block Repair](https://youtu.be/vm_I34zDGas)
[Cast Iron Crack Repair](https://youtu.be/Pq0wfU4ZaKk)
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