Well, although I am not an expert calculating things, there is a feat that caught my attention, and I am going to recalculate it, because whoever originally calculated it used incorrect values for certain things and therefore they no longer take said calculation into account.
So... I'm trying to recalculate this feat.
The first thing will be to calculate the measurements of the temporomandibular joints. The average jaw height of an adult male is 71.99 mm.
I'm sure in a discussion thread about this feat, they said cross sectional area should be used. A cross section is a 2-dimensional "cut" into a 3-dimensional figure. The cross section of a cylinder would then look like a circle, so we would have to do the formula for the area of a circle, which is A = pi x R^2. However, for the capsule it will be the area of an ellipse, because this the thickness of this capsule is 2.3 - 2.8 mm (1.38 - 1.4 mm is the result given by a child, further down the page they show the value of 2.3 - 2.8 mm, which should be best in this case, the average between 2.3 and 2.8 is 2.55 mm), while its length is greater than this and the area of an ellipse is calculated with A = R1 x R2 x pi. The lateral ligament is concave in shape, so I think it's okay to interpret its cross-sectional area as a circle.
Measurement calculations:
1- Lateral Ligament:
(27/85)x71.99 = 22.8674117647/2 = 11.4337058824 mm
Area of a Circle: 410.699245859 mm^2 o 4.10699245859 cm^2
2- Stylomandibular Ligament:
(13/95)x71.99 = 9.85126315789/2 = 4.92563157895 mm
Area of a Circle: 76.2208385747 mm^2 o 0.7622083857469999 cm^2
3- Sphenomandibular Ligament:
((19/95)x71.99)/2 = 7.199 mm
Area of a Circle: 162.814927369 mm^2 o 1.62814927369 cm^2
4- Joint Capsule:
((90/95)x71.99)/2 = 34.1005263158 mm
Area of an ellipse: 136.590702771 mm^2 o 1.36590702771 cm^2
Then:
If you see that I multiply x2, it's because there are two of these joints, one on each side of the jaw.
Total area (ligaments): (4.10699245859 + 0.7622083857469999 + 1.62814927369) x 2 = 12.9947002361 cm^2.
Total area (cartilage): 1.36590702771 x 2 = 2.73181405542 cm^2
The tensile strength of the flexor tendons is 10944 psi, or 769.43935 kg/cm^2.
The tensile strength of articular cartilage is 27.5 MPa, or 280.422 kg/cm^2.
Force required to tear off the jaw joints:
Tendons: 12.9947002361 x 769.43935 = 9998.63370311 kg
Cartilages: 2.73181405542 x 280.422 = 766.060761049 kg
Total force to tear off the jaw:
9998.63370311 + 766.060761049 = 10764.6944642 kg (Class 25)
However, I found another source that says that the tensile strength of ligaments and tendons varies between 50 and 150 MPa, we will use 50 MPa or 509.858 kg/cm^2 because I doubt that jaw ligaments are as strong as other ligaments of the human body.
(12.9947002361 x 509.858) + 766.060761049 = 7391.51263403 kg (Class 10)
So... which of these calculations should we use?
Low Range: 7391.51263403 kg (Class 10) (Accepted)
High Range: 10764.6944642 kg (Class 25)
If I made a mistake in math, in English (since it's not the language I regularly speak) or whatever, report it and I'll fix it.