For those of you who don't know, felling trees is incredibly dangerous. They store immense energy in a not terribly structurally safe form. Don't do it if you don't know what you are doing.

My dad always insists on cutting them himself and watching it always gave me a heart attack. That vid is basically what I play through in my head the whole time. So far nothing happened but man.

I remembering learning that the most powerful force acting on a building or tree was inertia. Watching videos like this makes that much more clear.