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Quiz Chapter 2: Pressure

10 questions · Form 5 Physics Bab 2: Pressure

10 questions · plays in fullscreen

Full Question List & Answer Key

Prefer reading to quizzing? All 10 questions are listed below with the answer and explanation under each one.

1. A wooden block floats in water with 60% of its volume submerged. What is the density of the wood? (Density of water = 1000 kg m⁻³)

  1. 600 kg m⁻³
  2. 400 kg m⁻³
  3. 1000 kg m⁻³
  4. 1200 kg m⁻³
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Answer: A

Floating condition: Weight = Buoyant Force => ρwood × Vtotal × g = ρwater × (0.60 Vtotal) × g => ρwood = 0.60 × 1000 = 600 kg m⁻³.

2. A block weighs 25 N in air and 18 N when fully submerged in water. What is the magnitude of the buoyant force acting on the block?

  1. 43 N
  2. 7 N
  3. 18 N
  4. 25 N
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Answer: B

Buoyant Force FB = Weight in air - Apparent weight in water = 25 N - 18 N = 7 N.

3. An open U-tube manometer contains water (density = 1000 kg m⁻³). When connected to a gas supply, the water level on the open arm is 20 cm higher than the arm connected to the gas. Taking Patm = 101,000 Pa and g = 9.81 m s⁻², calculate the gas pressure.

  1. 99,038 Pa
  2. 102,962 Pa
  3. 120,620 Pa
  4. 101,962 Pa
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Answer: B

Since open arm level is higher, Pgas = Patm + h ρ g = 101,000 + (0.20 × 1000 × 9.81) = 101,000 + 1,962 = 102,962 Pa.

4. A hydrometer is used to measure:

  1. Atmospheric pressure at different altitudes
  2. Gas pressure inside a sealed container
  3. Relative density of liquids based on flotation depth
  4. Flow velocity of liquids in pipes
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Answer: C

A hydrometer floats deeper in liquids of lower density and shallower in denser liquids, measuring relative liquid density.

5. Which factor does NOT affect the liquid pressure at the bottom of a container filled with water?

  1. Density of the water
  2. Depth of the water column
  3. Surface area of the base of the container
  4. Acceleration due to gravity
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Answer: C

From P = h ρ g, liquid pressure depends on depth, density, and gravity, but is completely independent of base area or container shape.

6. A solid block of volume 0.004 m³ is fully submerged in freshwater (density = 1000 kg m⁻³). What is the buoyant force acting on the block? (g = 9.81 m s⁻²)

  1. 39.24 N
  2. 4.00 N
  3. 3.92 N
  4. 392.40 N
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Answer: A

Buoyant force FB = ρ V g = 1000 × 0.004 × 9.81 = 39.24 N.

7. In a Venturi tube through which water flows horizontally, at which section is the fluid pressure the LOWEST?

  1. At the widest section where speed is highest
  2. At the narrowest constricted section where speed is highest
  3. At the inlet section before any constriction
  4. The pressure is uniform throughout the tube
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Answer: B

In a narrow constriction, fluid velocity increases to maintain mass flow rate. By Bernoulli's Principle, higher velocity leads to lower pressure.

8. Why does a suction cup stick tightly to a smooth wall surface after being pressed?

  1. Air trapped inside pushes out against the wall.
  2. Pressing evacuates air inside, causing higher atmospheric pressure outside to press the cup against the wall.
  3. Liquid pressure inside the cup binds it to the surface.
  4. Pascal's principle amplifies the user's pushing force.
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Answer: B

Pressing expels air, creating a low-pressure vacuum inside. External atmospheric pressure pushes firmly on the cup's outer surface.

9. How does a submarine submerge deeper under water?

  1. By pumping water out of its ballast tanks
  2. By flooding its ballast tanks with sea water to increase total weight
  3. By increasing the speed of its engine propeller
  4. By reducing the overall density of the ballast air
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Answer: B

Flooding ballast tanks increases the total weight of the submarine until weight exceeds buoyant force, allowing it to sink.

10. In a hydraulic system, if the input piston moves down by a distance of 15 cm, how far does the output piston move up if its cross-sectional area is 5 times larger than the input piston?

  1. 75 cm
  2. 3 cm
  3. 15 cm
  4. 5 cm
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Answer: B

By conservation of energy / volume displacement: A1 × d1 = A2 × d2 => A1 × 15 = (5 A1) × d2 => d2 = 155 = 3 cm.

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