Return to MCAT® Blog Homepage

MCAT Physics Question — Water Pressure

A holding tank at sea level (atmospheric pressure 1.01 x 105 Pa) containing water has a pressure of 2 x 105 Pa at 10 m depth. What is the pressure in an equivalent holding tank containing mercury (specific gravity = 13) at 1 m depth in Denver, CO (atmospheric pressure 8.4 x 104 Pa)?

 

A. 2 x 105 Pa

B. 1 x 105 Pa

C. 1.4 x 106 Pa

D. 8.4 x 104 Pa

Formula for hydrostatic pressure in a fluid:

Ptot = P0 + ρgh

Click for Explanation

Here, we can simply plug in the values provided:

Ptot = (8.4 x 104) + (13,000 kg/m3 x 10m/s2 x 1m) = 2.14 x 105 Pa

A. 2 x 105 Pa correct, matches our calculation

B. 1 x 105 Pa, incorrect, this is the same pressure at sea level for 10m of water, ignores fluid change and atmospheric pressure change

C. 1.4 x 106 Pa, incorrect, this answer fails to change the fluid depth to 1m for the mercury rather than the 10m depth used for water

D. 8.4 x 104 Pa, incorrect, this answer ignores the fluid contribution to pressure and only uses the atmospheric contribution

Want more MCAT practice?

We’ve got options for every schedule and learning style!

From the best online MCAT course created by top instructors with 524+ MCAT scores to the most representative full-length practice exams and private tutoring, we can custom tailor your MCAT prep to your goals!

Not sure which option is right for you? Schedule a free MCAT consultation with an MCAT expert using the form below. No obligation, just expert advice.

Create your Free Account to access our MCAT Flashcards SIGN UP NOW
MCAT is a registered trademark of the Association of American Medical Colleges (AAMC), which is not affiliated with Blueprint.