MCAT Physics Question — Absolute Pressure
- Apr 17, 2017
- MCAT Question of the Day
Click for Explanation
The atmospheric pressure exerted on the surface of the fluid is equal to 101,000 N/m2 (1 atm). To calculate the gauge pressure at each point, you must apply the formula, Pgauge = ρgh, where Pgauge is the pressure due to the water column of height h, ρ is the density of the fluid, g is the gravitational acceleration constant, and h is the depth.
Pabs (A) = Patm + Pgauge (A)
Pabs (A) = (101,000 N/m2)+ ρwaterghA
Pabs (A) = (101,000 N/m2) + (1000 kg/m3)(10 m/s2)(10 m)
Pabs (A) = 201,000 N/m2
Pabs (B) = Patm + Pgauge (B)
Pabs (B) = (101,000 N/m2)+ ρwaterghB
Pabs (B) = (101,000 N/m2) + (1000 kg/m3)(10 m/s2)(30 m)
Pabs (B) = 401,000 N/m2
Therefore, the PB = 2PA making answer choice A the correct answer. Furthermore, an increase in depth of 10 m in water equals 1 atmosphere. Therefore, the total pressure at A is 2 atm while the total pressure at B is 4 atm.
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