general physics
posted by please help with these practice problems on .
A solid concrete block weighs 160 N and is resting on the ground. Its dimensions are 0.400 m x 0.240 m x 0.0950 m. A number of identical blocks are stacked on top of this one. What is the smallest number of whole bricks (including the one on the ground) that can be stacked so that their weight creates a pressure of at least two atmospheres on the ground beneath the first block? (Hint: First decide which face of the brick is in contact with the ground.)

p = 2 atm = 202650 Pa
p₀ = mg/a•b = 160/0.4•0.24 =1667 Pa
N = p/p₀ =202650/1667=121.6 ≈122 
The answer from Elena is almost correct. The question asks for the least number of bricks, so you would actually use the smallest side of the brick to stack them.
Po = 160 / (.24*.095) =~ 7018 Pa
N = 202650 / 7018 = 28.9 = 29 Bricks.