Found this on Quora, what do you guys think?
https://www.quora.com/How-much-force-does-it-take-to-rip-off-a-persons-head-with-one-hand
And I quote[]
If I grabbed someone by the neck using a rope which was tied to a rappel harness with 240 kg and I weigh 80 kg and jump 4 meters into water using a 3 meter rope length doubled overall, I believe this amount of weight on the line which goes taut at 3 meters will produce 9408 Newtons which is my calculation and hypothesis for the amount of force required to decapitate someone with one or two hands, considering you can hold on to your rappel line without difficulty with one hand and prepare for the snap. You should jump over water as the 240 kgs that is attached to your harness will need some where to go once the head is off. You will need to watch for the huge amount of blood, and release your rope from the harness by preparing for use of quick release attachments ahead of time or else you will get taken into the water with the head and 240 kilos of weight.
My estimation is 3 m drop of 320 kg =9408 joules =6938 ftlbs =9406 Nm =959 kgf
I would like to also draw some attention on the wikipedia article on Hanging which I know many researchers refer to without pausing to see that the equivalence of frtlb is not correct when converted to Nm and does not equal the given value of Nm however the Nm is correctly equivalenced to Kgf (This occurs twice for two different ftlb values in the same article)
My estimation is 3 m drop of 320 kg =9408 joules =6938 ftlbs =9406 Nm =959 kgf
Wikipedia has a figure of 1260 ftlb ( 5600 Newtons or 572 kgf )
actually 1260 ftlb = 1708Nm = 174 kgf
and 1000 ftlb (4400 N = 450 kgf) perhaps this means something other than it seems.