OAR Mechanical Comprehension: Fluids Questions and Answers Flashcards

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?

Answer: 100 lb

By Pascal's principle, force multiplies by the area ratio: 10 × (20/2) = 100 lb.

What happens to the buoyant force on a fully submerged object as it is pushed deeper into a fluid of uniform density?

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.

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?

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.

A submarine's hull must withstand greater pressure at deeper depths primarily because of which factor?

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.

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?

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%.

In a venturi meter, what happens to the fluid pressure in the constricted (narrow) section compared to the wider section?

Answer: Pressure decreases

According to Bernoulli's principle, as fluid velocity increases in the narrow section, pressure decreases.