OAR OAR Mechanical Comprehension: Fluids Questions and Answers 2 — Questions and Answers
Question 1: A hydraulic jack has a small piston with an area of 2 sq in and a large piston with an area of 20 sq in. If 10 lb of force is applied to the small piston, what force is exerted by the large piston?
- 100 lb (Correct answer)
- 200 lb
- 20 lb
- 50 lb
Correct answer: 100 lb
By Pascal's principle, force multiplies by the area ratio: 10 × (20/2) = 100 lb.
Question 2: What happens to the buoyant force on a fully submerged object as it is pushed deeper into a fluid of uniform density?
- It remains the same (Correct answer)
- It increases
- It decreases
- It doubles
Correct answer: It remains the same
Buoyant force depends only on displaced volume and fluid density, both of which remain constant as the object goes deeper.
Question 3: Water flows through a horizontal pipe that narrows from a diameter of 4 cm to 2 cm. How does the flow velocity change in the narrow section?
- It quadruples (Correct answer)
- It doubles
- It stays the same
- It halves
Correct answer: It quadruples
By the continuity equation, velocity is inversely proportional to cross-sectional area, and halving the diameter reduces area by a factor of four, so velocity quadruples.
Question 4: A submarine's hull must withstand greater pressure at deeper depths primarily because of which factor?
- The increasing weight of the water column above it (Correct answer)
- The temperature of the water
- The salinity of the ocean
- The speed of ocean currents
Correct answer: The increasing weight of the water column above it
Hydrostatic pressure increases with depth due to the weight of the fluid column above, as described by P = ρgh.
Question 5: An object with a density of 0.6 g/cm³ is placed in water (density 1.0 g/cm³). What fraction of the object's volume will be submerged?
- 60% (Correct answer)
- 40%
- 100%
- 50%
Correct answer: 60%
A floating object displaces fluid equal to its own weight, so the submerged fraction equals the ratio of object density to fluid density: 0.6/1.0 = 60%.
Question 6: In a venturi meter, what happens to the fluid pressure in the constricted (narrow) section compared to the wider section?
- Pressure decreases (Correct answer)
- Pressure increases
- Pressure stays the same
- Pressure fluctuates randomly
Correct answer: Pressure decreases
According to Bernoulli's principle, as fluid velocity increases in the narrow section, pressure decreases.
OAR OAR Mechanical Comprehension: Fluids Questions and Answers 2
A hydraulic jack has a small piston with an area of 2 sq in and a large piston with an area of 20 sq in.
If 10 lb of force is applied to the small piston, what force is exerted by the large piston?