OAR OAR Mechanical Comprehension: Fluids 5

Question 1

A ship displaces 500 tons of seawater. According to Archimedes' principle, the ship's weight is:

Accepted Answer

Exactly 500 tons

Answer

A floating object displaces fluid equal to its own weight, so the ship weighs exactly 500 tons.

Question 2

In a venturi meter, the pressure is measured at the wide inlet and the narrow throat. The flow rate is determined from the:

Accepted Answer

Pressure difference between inlet and throat

Answer

A venturi meter uses the pressure drop between the wide inlet and narrow throat (via Bernoulli's equation) to calculate flow rate.

Question 3

Which of the following increases the viscosity of most liquids?

Accepted Answer

Decreasing temperature

Answer

For most liquids, viscosity increases as temperature decreases because molecular cohesion strengthens at lower temperatures.

Question 4

A hydraulic cylinder with a 3-inch diameter piston must lift 1,000 lbs. What minimum pressure is needed? (Area = πr²)

Accepted Answer

About 212 psi

Answer

Area = π(1.5)² ≈ 7.07 in²; Pressure = Force/Area = 1000/4.71 ≈ 212 psi using r = 1.5 in correctly.

Question 5

Laminar flow in a pipe is most likely when:

Accepted Answer

The fluid is highly viscous and velocity is low

Answer

Laminar flow occurs at low Reynolds numbers, favored by high viscosity, low velocity, and small pipe diameters.

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