Final answer:
To create a pressure of two atmospheres, we need to stack 96 concrete blocks on top of the first one, as each block weighs 169 N and the area they cover is 0.08 m².
Step-by-step explanation:
To calculate the minimum number of concrete blocks needed to create a pressure of at least two atmospheres on the ground beneath the first block, we first need to understand that one atmosphere of pressure is 1.01 × 105 N/m². Therefore, a pressure of two atmospheres would be 2.02 × 105 N/m². The area over which the blocks exert pressure on the ground is 0.4m * 0.2m = 0.08 m². Dividing the required pressure by this area gives us the total force needed to create this pressure.
To calculate the force needed: 2.02 × 105 N/m² × 0.08 m² = 16160 N. Given that one block has a weight of 169 N, we need to stack enough blocks so their total weight equals or exceeds 16160 N. Therefore, the number of blocks needed is 16160 N divided by 169 N per block, which gives approximately 95.6 blocks. Since we cannot have a fraction of a block, we'd need 96 blocks in total (including the one on the ground) to create the desired pressure.