Answers Fluid Statics

Unit 27: Pressure & Manometers

Q27.1) a) 152 000 Pa

b) 152 kPa

c) 1.52 bar

d) 22 psi

e) 1140 mmHg

Q27.2) An absolute pressure is measured relative to a perfect vacuum (absolute zero pressure), while a gauge pressure is measured relative to atmospheric pressure. The absolute pressure of the atmosphere at sea level is 101 000 Pa (1 atm), and the gauge pressure of the atmosphere at sea level is zero. 180 kPa of absolute pressure is 79 kPa of gauge pressure.

Q27.3) 10.3 m

Q27.4) 218.8 kPa (absolute), 117.8 kPa (gauge)

Q27.5) 2667 kg/m³

Q27.6) 682 Pa

Unit 28: Atmospheric Pressure & the Barometric Equation

Q28.1) 33 331 Pa

Q28.2) 12 850 m

Q28.3) 24.1 kPa

Q28.4) a) 3.7 m/s²

b) 40.5 km

c) 1.36 Pa

d) It would be much more difficult to sustain flight on Mars compared to on Earth. You might think it would be easier because of the reduced gravity, but remember that atmospheric pressure is proportional to atmospheric density. Mars’ extremely low atmospheric pressure means it has a very thin atmosphere. If you were to take a volume of Earth air containing 1000 molecules, the same volume of Martian air would contain only 6 molecules. The amount of lift one can generate is proportional to the mass of air one can displace, so it’s much more difficult to generate sustained lift on Mars compared to Earth.

Unit 29: Surface Tension & Bubbles

Q29.1) 7.28 x 10⁻⁶ J

Q29.2) 145.6 Pa

Q29.3) 291.2 Pa

Q29.4) A

Q29.5) 196 291 Pa (absolute), 95 291 Pa (gauge)

Q29.6) 0.707

Q29.7) 107 033 Pa (absolute), 6033 Pa (gauge)

Q30.1) 2.97 cm

Q30.2) rise 0° < θ < 90°, fall 90° < θ < 180°

Q30.3) 0.83 cm

Q30.4) 1.41 cm

Unit 30: Capillary Action

Unit 31: Buoyancy & Archimedes’ Principle

Q31.1) A = B < C = D

Q31.2) 1195 kg/m³

Q31.3) 9.7 %

Q31.4) 77%

Q31.5) 11.6 %