Uncle Jed’s Iron cleaver

[Sam Colt]

What sort of wizardry is this?

 

[deemus]

That’s the size mine is but it ain’t that sharp.

 

[TXAZ]

Basic physics. The blade is very sharp, so the force to penetrate the sidewall is small.
The angle is steep~45 degrees, so the imparted vertical force is about the same as the horizontal force (which would knock it off the tripod).
The inertia from the mass of the water not wanting to move, plus the additional downward force from the blade, times the static friction coefficient is more than the force required to move the bottle so it doesn’t slide off.

Homework for the reader: at what angle of slice will the bottle start to move before the cut is made? (Hint: It could be slightly upward)

Thanks, stuff like this is why teaching physics was fun!

 

[TXAZ]

PS: the top of the uneven tripod could also help the bottle stay in place.

 

[TreyG-20]

Basic physics. The blade is very sharp, so the force to penetrate the sidewall is small.
The angle is steep~45 degrees, so the imparted vertical force is about the same as the horizontal force (which would knock it off the tripod).
The inertia from the mass of the water not wanting to move, plus the additional downward force from the blade, times the static friction coefficient is more than the force required to move the bottle so it doesn’t slide off.

Homework for the reader: at what angle of slice will the bottle start to move before the cut is made? (Hint: It could be slightly upward)

Thanks, stuff like this is why teaching physics was fun!

Shot in the dark. 100°?

 

[Texasjack]

Oh, there's so much wrong here. First question: Why is my cleaver not that sharp? Because nobody who makes a cleaver to be USED as a cleaver would ever use that angle for the edge. The knife in the video has a lot of mass with a very shallow angle, so it does cool cuts on ropes or bottles, but wouldn't be worth much for butchering. Next, look at the bottle. It's not full. Full bottles are used for contests because the water is not compressible and so a blade has to be super sharp to make it through. This bottle is half empty, so he's just cutting plastic and not having to deal with the resistance of the water. It all looks cool, but it's not practical.