The diagram shows the cross-section of an Olympic-size swimming pool filled with water.

Question 18

The diagram shows the cross-section of an Olympic-size swimming pool filled with water. It is not drawn to scale. The density of the water is 1000 kg m^-3.

What is the difference in pressure between X and Y?

A 0.35 kPa                  B 3.4 kPa                    C 21.3 kPa                  D 58.9 kPa

Reference: Past Exam Paper – November 2015 Paper 12 Q20

Solution:

Answer: B.

Pressure is due to the liquid above the point.

Pressure in liquid = hρg

where h is the depth under water

Pressure at X = hρg = 2.35 × ρg

Pressure at Y = hρg = 2.00 × ρg

Difference in pressure = pressure at X – pressure at Y

Difference in pressure = 2.35 × ρg – 2.00 × ρg = (2.35 – 2.00) × 1000 × 9.81

Difference in pressure = 3433.5 Pa = 3.4 kPa