(2) According to "B cuts a part in the vertical direction and piles it right above A, at this time, the pressures of A and B on the ground are equal",
P' A =P B,F' A S A =ρgh B,
G A +△G B S A =ρgh B,
Then ρ×8h3×g+ρ△h×9h2×g4h2=ρg3h,
The solution is △ h = 49 h
Answer: (1) The pressure on the ground is1960 P A; ;
(2) The cutoff thickness △h of cube B is 49 h. 。