Pressure & 3 Principles

Pressure of liquid depends on

• Mass

• Volume

• Density

• surface area

Compare the pressure, P_A and P_B

• P_A > P_B

• P_A < P_B

• P_A = P_B

If the density of sea water is 1150 kgm-3, calculate the pressure below 40m of sea water due to

the water alone. [g = 10 N/kg]

• 350 kPa

• 460 kPa

• 520 kPa

The figure shows a cylinder containing liquid mercury. What is the pressure caused by the liquid mercury at the point P?

[Density of liquid mercury is 1.36 x 10^4 kgm-3, g = 10 N/kg]

• 72.3 kPa

• 81.6 kPa

• 92.3 kPa

pressure caused by the weight of the air above us. This refer to

• Liquid pressure

• Gas pressure

• Atmospheric pressure

Which equation is correct to find gas pressure?

• P_gas = P_atm + h

• P_gas = P_atm - h

• P_gas = P_atm

The figure shows a manometer containing mercury is connected to a gas supply. Calculate the pressure of the gas supply in the units cm Hg and Pa

[ Density of mercury = 1.36 x 10^4 kg m-3 and Atmospheric pressure = 76 cm Hg ] [g=10 N/kg]

• 15 cmHg, 120 kPa

• 15 cmHg, 124 kPa

• 91 cmHg, 120 kPa

• 91 cmHg, 124 kPa

When pressure is applied to an enclosed fluid, the pressure will be transmitted equally throughout the whole enclosed fluid. This refer to which principle?

• Pascal’s Principle

• Bernoulli’s Principle

• Archimedes’ Principle

The figure shows a basic hydraulic system has small and large pistons with cross-sectional area of 0.005 m2 and 0.1 m2 respectively. A force of 20 N is applied to the small piston. Determine the pressure transmitted in the hydraulic fluid.

• 3 000 Pa

• 4 000 Pa

• 5 000 Pa

An object is hung from a spring.

a) What is the buoyant force on the object in water?

b) What is the weight of water displaced by the object?

• 30 N, 35 N

• 30 N, 30 N

• 35 N, 30 N

• 35 N, 35 N