Diver Down 3

Now suppose you weld a cover to the top of the 10-m deep tank while leaving a small hole in the top. Then you weld a skinny, 10-m long pipe to the hole and fill it with about a gallon of water. What pressure does the diver at the bottom measure?

A) A bit more than 1 atmosphere

B) About 2 atmospheres

C) About 3 atmospheres

D) About 10 atmospheres

E) Something else

Solution: C. Use the formula for pressure in a static fluid with the new depth, 20 meters. P = P₀ + ρgd = 1.013E5 + 1000*9.8*20 ≈ 3E5 Pa ≈ 3 atm. The shape of the container is not relevant. As long as the fluid is static and we know the depth below the reference point, we can calculate the pressure with confidence.