OAR Mechanical Comprehension: Fluids Flashcards

A submarine descends from 100 ft to 200 ft below sea water. What happens to the pressure on its hull?

Answer: Pressure increases but does not double because surface pressure already exists

Total pressure = atmospheric + hydrostatic; doubling depth doubles only the hydrostatic component, so total pressure increases but does not double.

Which property of a fluid describes its resistance to flow?

Answer: Viscosity

Viscosity is the measure of a fluid's internal friction and resistance to deformation or flow.

Water flows at 3 ft/s through a pipe with a 6 in² cross-section. What is the volumetric flow rate?

Answer: 0.125 ft³/s

Q = A × v = (6/144 ft²) × 3 ft/s = 0.125 ft³/s (convert 6 in² to ft²).

A sealed container is partially filled with water and then heated. What happens to the pressure inside?

Answer: Pressure increases because water vapor pressure rises

Heating increases vapor pressure and thermal expansion in a sealed container, raising internal pressure.

Two connected tanks at the same elevation are filled with water. If Tank A has a larger cross-sectional area than Tank B, at equilibrium the water level in each tank is:

Answer: Equal in both tanks

Connected static fluids of the same type reach equal heights regardless of tank size (hydrostatic equilibrium).

What does a manometer measure?

Answer: Pressure difference between two points

A manometer uses a column of liquid to measure the pressure difference between two fluid regions.

An object submerged in water weighs 10 lbs when measured underwater and 25 lbs when measured in air. What is the buoyant force?

Answer: 15 lbs

Buoyant force = weight in air − weight in fluid = 25 − 10 = 15 lbs.