Quote Originally Posted by Taeth
Quote Originally Posted by landmine950
I have an Engineering Degree from U of A

PSI is of course pounds of force per square inch.

you can generate 1000' of PSI with a small force if the application area is small..

eg push on a thumbtack.
the force of your thumb is say 10 pounds but the area of the point of the pin is say 1000 th of a square inch. the result is 10,000 psi

conversely small forces on large areas can create huge forces such as the lift on an airplane wing or the force holding up a inflated stadium roof that might weight 1,000,000 pounds held up by a pressure differential of only a fraction of a PSI.

Its very hard to calculate the force of a punch because of the factors involved
Generally force is mass times acceleration.
So if a boxer punches a measured mass the acceleration of the mass can be measured and the punching force determined
But a heavier puncher maintains the acceleration of the mass longer than a lighter puncher who's kinetic energy is dissipated faster, the body mass behind the punch and muscles that continue to drive it forward MUST BE CONSIDERED.
it's NOT EASY.

so the methods of punching something that weighs about the same as a mans head and seeing how far it flys (relates to acceleration) are not really accurate.
Foreman didn't have fast hands but he hit hard!
The hard part in measuring the force of a punch without using PSI is because its hard to know how much momentum or mass is actually behind the punch. Acceleration changes the force of the punch, but it is at a fixed rate at the exact moment it hits the opponent. Not only the body mass which acts fulcrum point, but also the alignment of the arm, and bone density also play a factor.
You wouldn't measure the acceleration of the fist,as you rightly stated the fist is at a certain speed at the time of contact.
The force of the punch would be determined by measuring the acceleration it creates on the object it hits.

ie the stationary head with a certain mass is accelerated backwards, from V=O to some speed over a short time period.
Determining this acceleration and knowing the mass of the test object being punched allows a crude calculation of the force of the punch. this is how the punching bags in bars etc work.
A fulcrum could be used to convert the punch force to a lifting force sort of like the strong man circus hammer strength tests. and the acceleration of the known weight which flys up and hit a bell is easily calculated using
d= 1/2 A * t^2 where A is 9.81 m/s^2

The other things you say are all true. the force must be maintained during the transfer of energy as the collision is not perfectly ellastic ie forces are dissipated in other places such as deformation of the glove (and face) and the movement of the punchers body etc.