I am attempting to determine a method for calculating the final pressure in a deformable bladder given a starting pressure and an applied load. Scenario: This is actual data gathered in my lab: A) You have a ball made from a rubbery material with P1=3psi. You weigh 150lbs and step on the ball, and the internal pressure P2=13psi. B) The same ball is pressurized to P1=10psi. Applying the same load as before (150lbs), P2=16psi. Question: 1) Why does applying the same load in both cases not increase the internal pressure by an equal amount (why does the starting pressure matter)? 2) Without knowning the characteristics of the ball (elastic modulus, etc.), is there any way to calculate the resulting preesure (P2)? Would the internal surface area of the ball be of any assitance?