Chapter 3.2 Pressure in Liquids

When blood pressure is measured, the cuff of the sphygmomanometer is wrapped round the upper arm and must be held at the level of the heart. Why?

• Blood pressure depends on the level of the blood.

• Blood pressure is normal when the cuff and heart are at the same level.

• Blood is able to flow easily to the wrist.

The pressure of sea water at the bottom of the sea is 1.2 × 108 N m–2.

Determine the depth of the sea.

[Density of sea water = 1020 kg m^–3]

• 1.18×10⁴ m

• 1.18×10⁵ m

• 1.18×10⁶ m

• 1.18×10⁹ m

Diagram shows a U-tube filled with two liquids, X and Y which are immiscible. The heights of the liquid columns of X and Y from level P are 8 cm and 4 cm respectively. Which of the following statements is true?

• The density of X is less than the density of Y.

• The liquid pressure is higher in column X than in column Y at level P.

• The densities of liquids X and Y are equal.

Diagram shows the design of a dam. Why does the thickness of the dam increase with its depth?

• The design of this structure is stronger.

• Water pressure increases with depth.

• The cost of construction is lower.

• Water pressure acts uniformly in all directions.

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A submarine has a surface area of 300 m².

The density of sea water is 1050 kg m^–3.

At what depth under the sea, will the additionalpressure on the submarine be 5 × 10⁵ Pa?

[Take g = 10 N kg^–1]

• 47.62 m

• 67.62 m

• 87.62 m

• 57.62 m

The figure below shows a reservoir on a hill. The reservoir supplies water to a water tank on a tall building.

Calculate the water pressure at X.

(Density of water = 1000 kg m^–3)

• 1.4×10⁹ Nm^–2

• 1.4×10² Nm^–2

• 1.4×10⁵ Nm^–2

• 1.4×10⁸ Nm^–2

A coin sinks to a depth of 5 m in a liquid of density 800 kg m^–3. At what depth, in a different liquid of density 600 kg m^–3, will the coin be subjected to the same pressure?

• 6.67 m

• 8.67 m

• 9.67 m

• 5.67 m

The figure shows a pond with two fish P and Q.

What is the correct relation of the water pressures on fish P and fish Q?

• Water pressure on fish Q > Water pressure on fish P.

• Water pressure on fish Q < Water pressure on fish P.

• Water pressure on fish Q = Water pressure on fish P.