Atmospheric pressure at sea level has a value of 100 kPa. The density of sea water is 1020 kg m-3. At which depth in the sea would the total pressure be 110 kPa?

Question 5

Atmospheric pressure at sea level has a value of 100 kPa.

The density of sea water is 1020 kg m^-3.

At which depth in the sea would the total pressure be 110 kPa?

A 1.0 m                       B 9.8 m                       C 10 m                        D 11 m

Reference: Past Exam Paper – November 2014 Paper 13 Q20

Solution:

Answer: A.

Let the depth in the sea at which the pressure is 110 kPa be h.

The pressure at h is due to the amount of water above the point and due to the atmospheric pressure at sea level.

Pressure at depth h = Pressure due to height h of sea water + Atmospheric pressure

110 000 = hρg + 100 000

hρg = 10 000

Depth h = 10 000 / (ρg) = 10 000 / (1020×9.81)

Depth h = 0.9993 = 1.0 m