Why is packing tape nearly impossible to tear when intact, but easily shreds if you cut the slightest nick into it?

Question

Why is packing tape nearly impossible to tear when intact, but easily shreds if you cut the slightest nick into it?

In: 6079

Answer 1

As I remember from college…

If you have a piece of paper with a tear in it, and you pull it on both sides of the tear, the pulling force around the endpoint of the tear can be up to 3 times as high as the average pulling force across the whole paper. (It depends on the length of the tear.)

So yes it is much easier to rip apart, as it’s now easier to get over the threshold, and it will tear starting from the end point of the tear.