Your Pressure Today

If mercury in a barometer is replaced by water, the height of 2 cm of mercury will be following _____ cm of water.

• 27.2

• 50

• 50.2

• 27

Answer explanation

On a sea-level standard day, a pressure gauge reads a gauge pressure of 1.3 MPa below the surface of the ocean (SG of seawater = 1.025). How deep is the instrument?

• 7 m

• 4 m

• 133 m

• 129 m

Answer explanation

Which one of the following laws is applicable to a hydraulic lift?

• Kirchhoff's Law

• Pascal's Law

• Archimedes' Pronciples

• Archimedes' Law

Answer explanation

The Pascal's Law states that in fluid which is at rest in a container, the pressure applied to one part of the fluid is uniformity transmitted to all the parts of the fluid.

Key Points:

• - A hydraulic lift employs this principle to lift heavy objects.

• - When pressure is applied to a fluid through one piston, it results in ad equivalent pressure on another piston in the system which is then able to lift objects.

• - With the increase in the area of the second piston, the force exerted by it also increases thus enabling lifting of heavier objects.

Which of the following is NOT a characteristics of the liquid used in a manometer?

• The liquid should stick on the walls

• High viscosity

• Low surface tension

• It should be immiscible

Answer explanation

A manometer is a device that measures pressure by balancing a column of liquid against a column of gas or another liquid. the liquid used in a manometer should have the following characteristics:

• - The liquid should stick on the walls: The liquid used in a manometer should stick to the walls of the tube to prevent it from flowing back and forth due to vibration or turbulence.

• - Low surface tension: The liquid used in a manometer should have low surface tension to ensure that the meniscus does not significantly affect the pressure reading.

• - It should be immiscible: The liquid used in a manometer should be immiscible with the gas or liquid being measured, to prevent the two fluids from mixing and affecting the accuracy of the pressure measurement.

• - High Viscosity is NOT a desirable characteristic for a manometer liquid. A highly viscous liquid will not respond quickly to changes in pressure, leading to slow and inaccurate readings. Thus, manometer liquids are typically chosen to have relatively low viscosity.

When a dolphin glides through the air, it experiences an external pressure of 0.75 m of mercury. The absolute pressure on a dolphin when it is 5 m below the free surface of the water is_____.

• 0.10 N/mm2

• 0.5 N/mm2

• 1.0 N/mm2

• 0.15 N/mm2

Answer explanation