Andrew,
John Farley gave you the good oil.
Prof2MDA is a bit off in his last para. He is mixing up the deceleration experienced by the passenger with the deceleration experienced by the aircraft.
Think about sitting on a piece of aluminium which is allowed to free-fall to the ground. The aluminium is called airplane. Result. Sore bum. Because the aluminium is incompressible, the deceleration experienced by it, and your bum, are the same.
Put a piece of sponge between your bum and the aluminium. Your deceleration is slower. It takes longer to reduce your vertical velocity to zero. So your bum has an easier landing. The aluminium has an easier landing because your bum takes longer to add its full weight.
Put a piece of sponge between the aluminium and the ground. The aluminiun will now have a softer landing. And if you still have the sponge under your bum, it will be softer still. (so far as you are concerned)
The point I am trying to make is that landing deceleration forces depend on what you are in the system which is decelerating.
Mr. Boeing could design aircraft with rigid seats, so that you (the passenger) became effectively part of the airplane. Then the deceleration you experience on landing will depend on the rate at which the vertical velocity will be absorbed by the oleos and tyres.
But Mr. Boeing is stuck with a system where (I'm guessing) 90% of the landing system is rigid (ie airplane and freight), with only the oleos and tyres to arrest its vertical velocity on landing. The other 10% (you and me on our padded seats) have the added deceleration distance of the depth of our cushioned seats. So the rigid airplane will experience one deceleration, and the floating passengers will experience another (lesser) deceleration.
See Tech Log thread "G and its real meaning" November 2000
I REPEAT. If you want to fly airplanes, get stuck into trigonometry. IT IS VERY IMPORTANT TO YOU, AND NOT DIFFICULT.