10 questions · Form 5 Physics Bab 2: Pressure
In a hydraulic jack, a force of 40 N is applied to a small input piston of area 0.02 m². What force is exerted by the large output piston of area 0.5 m²?
Prefer reading to quizzing? All 10 questions are listed below with the answer and explanation under each one.
1. In a hydraulic jack, a force of 40 N is applied to a small input piston of area 0.02 m². What force is exerted by the large output piston of area 0.5 m²?
Answer: A
By Pascal's Principle, F1 / A1 = F2 / A2 => 400.02 = F2 / 0.5 => 2000 = F2 / 0.5 => F2 = 1000 N.
2. If a hydraulic brake pedal force of 50 N produces a fluid pressure of 250 kPa, what is the area of the master cylinder piston?
Answer: A
P = FA => 250,000 Pa = 50 N / A => A = 50250,000 = 0.0002 m².
3. A hydrometer is used to measure:
Answer: C
A hydrometer floats deeper in liquids of lower density and shallower in denser liquids, measuring relative liquid density.
4. 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?
Answer: B
By conservation of energy / volume displacement: A1 × d1 = A2 × d2 => A1 × 15 = (5 A1) × d2 => d2 = 155 = 3 cm.
5. A diver descends to a depth of 15 m in seawater of density 1025 kg m⁻³. What is the liquid pressure experienced by the diver due to seawater alone? (Take g = 9.81 m s⁻²)
Answer: A
Liquid pressure P = h ρ g = 15 × 1025 × 9.81 = 150,922.5 Pa ≈ 150,922 Pa.
6. A mercury barometer reads a height of 76 cmHg. What is this atmospheric pressure value in Pascals? (Density of mercury = 13,600 kg m⁻³, g = 9.81 m s⁻²)
Answer: A
P = h ρ g = 0.76 m × 13,600 kg m⁻³ × 9.81 m s⁻² = 101,396.16 Pa ≈ 101,396 Pa.
7. Which factor does NOT affect the liquid pressure at the bottom of a container filled with water?
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.
8. Why is oil used instead of air as the working fluid in hydraulic systems?
Answer: B
Hydraulic fluids must be incompressible so that applied pressure is transmitted directly and completely without loss to fluid volume change.
9. Two ping-pong balls are suspended close to each other on strings. When air is blown rapidly into the gap between them, what happens?
Answer: B
Fast-moving air in the gap creates a low-pressure region (Bernoulli's Principle). Higher atmospheric pressure outside pushes the balls together.
10. How does a submarine submerge deeper under water?
Answer: B
Flooding ballast tanks increases the total weight of the submarine until weight exceeds buoyant force, allowing it to sink.