1. The problem statement, all variables and given/known data A 55kg cheerleader uses an oil-filled hydraulic lift to hold four 110 kg football players at a height of 1 m. If her piston is 16 cm in diameter, what is the diameter of the football players' piston? 2. Relevant equations 3. The attempt at a solution (55kg)(9.80)/(.02 m^2) = (440kg)(9.80)/A2 A2 = .16 m^2 .16 m^2 = pi * r^2 r=.2257 m D= .45 m = 45 cm Is this correct? I am a little bit confused as to the difference between these formulas: p0 + F1/A1 = p0 + F2/A2 + ro*gh This is the one I used because she is just holding them in position and no work is being done. for the formula DeltaF = ro*g (A1+A2)d2 You should use this one when the problem involves lifting something (doing work)