Why is it hard to cut something from the outside, but if you punch a hole it’s suddenly much easier?

Question

Let’s say I take a tube. If I try to cut with a knife, it just wont work. However if I take the tip and cut a hole, I can then suddenly cut with the knife the entire thing.

In: Physics

Answer 1

You’re taking the same force that was once low pressure on a large area, and turning it into high pressure on a low area. That gets you into the tube. Then, you already have a material failure, and things hold together better when there’s no failure points.