Each stride an adult takes places 900 psi on the bottom of the foot? how to calculate?

Question

That's what a podiatrist told me, but that sounds just crazy. It seems like just standing, my weight is putting about 3 psi on the bottom of my feet. A rottweiler's bite is 800 psi. It seems like I would have to fall pretty far to generate that much force...Can anyone tell me how to calculate it? (assume 175 lbs, 36 square inches of sole) I know it has something to due with acceleration due to gravity, like force = mass X acceleration, but how do I figure in height, convert newtons to pounds, etc.?

Answer 1

Pressure is force over area. True. However when you walk it's the momentum that impacts your feet or actually it is the change in momentum that generates that force.  In other words how fast the ground stops your motion. Also the impact area is not your entire sole but mostly your heel.

900 PSI? May be excessive but... Well it also depends on shoes. Does it not?

Lets say your foot moves towards the ground at say 4 ft/s, the momentum is thus

p=mV= (100/32) x 4= 12.5 sl ft/s

lets say it takes 10ms for the ground to stop you then

F= p/t = 12.5 / 0.010= 1250 lb (WOW!)

What is the impact area A?

P= F/A (...and here we are)