Applejack is a Vine-Chopping Double-Airplane.

Think for a second about the nearly impossible amount of strength it would take to cut a living vine the thickness of a small tree with something as dull as a window without being able to build any momentum.

Alright, let’s do this.

Applejack exerted a certain amount of psi onto a large vine and broke it. How much psi can Applejack generate without a sweat?

We’ll work in SI units in this exercise.

One pascal (SI unit of pressure) is N / m^2 

Let’s first find how many pascals the windowframe first exerts on the vine because of gravity.

N = 9.8 (the gravitational pull of the earth).

A dull window would have a large area exerting force, compared to a sharp, small edge. Various window measurements from Home Depot's website and my house reveals that an average window's edge dimensions are roughly 3/4 inches x 36 inches. An inch is 0.0254 meters.

3/4 * 36 * 0.0254 = 0.6858 meters squared.

m = 0.6858 meters squared.

Let’s calculate.

p = N / m^2

p = 9.8 / 0.6858

p ~= 14.29 pascals

The window exerts 14.29 pascals on the vine naturally.

Let’s assume the vine is made of black oak. The tensile strength of black oak is 6,520 psi (when the oak compresses and crushes). Wolfram|Alpha tells me that that is equal to 44,950,000 pascals. Woah. Let’s subtract the natural gravitational pascals from the overall tensile strength to find out how much Applejack has to exert manually.

44950000 - 14.29 = 44949985.7 pascals

There’s our answer (a lot). But how much is that in psi? Let’s have Google finish it off.

44949985.7 pascals = 6519.44424 pounds per square inch.

Applejack has to exert about 6519.44424 psi of pressure onto the vine. That’s just about the equivalent of twoairplane hydraulic systems.

Applejack for best vine-chopping double-airplane, 2013.

_{I did not math this. Thanks to SgtPiggy for the calculations.}