Nursing Elites

1. Longitudinal waves have vibrations that move ___________.

• A. at right angles to the direction of the vibrations
• B. in the direction opposite to that of the wave
• C. in the same direction as the wave
• D. in waves and troughs

Correct answer: C

Rationale: In longitudinal waves, the vibrations of particles occur in the same direction as the wave propagates. This means the particles move back and forth in the direction of the wave, creating compressions and rarefactions along the wave. Therefore, the correct choice is C, in the same direction as the wave. Choice A is incorrect because transverse waves, not longitudinal waves, have vibrations at right angles to the direction of wave propagation. Choice B is incorrect as it describes the motion in transverse waves. Choice D is incorrect as it is an inaccurate representation of how longitudinal waves propagate.

2. What is the primary factor responsible for generating lift on an airplane wing?

• A. Propulsion force generated by the engines
• B. Buoyant forces acting on the entire aircraft
• C. Drag reduction achieved through streamlining
• D. Application of Bernoulli's principle to the airfoil's shape

Correct answer: D

Rationale: The primary factor responsible for generating lift on an airplane wing is the application of Bernoulli's principle. This principle states that the air moving over the curved top surface of the wing has to travel faster, leading to reduced pressure above the wing and creating lift. Engines provide thrust for propulsion, not lift. Buoyant forces are more relevant to lighter-than-air aircraft like balloons or airships, not airplanes. While drag reduction through streamlining is important for efficiency, it is not the primary factor in lift generation. Therefore, the correct answer is D.

3. A closed system undergoes a cyclic process, returning to its initial state. What can be said about the net work done (Wnet) by the system over the entire cycle?

• A. Wnet is always positive.
• B. Wnet is always negative.
• C. Wnet can be positive, negative, or zero.
• D. Wnet is equal to the total heat transferred into the system (dQ ≠ 0 for a cycle).

Correct answer: C

Rationale: For a closed system undergoing a cyclic process and returning to its initial state, the net work done (Wnet) over the entire cycle can be positive, negative, or zero. This is because the work done is determined by the area enclosed by the cycle on a P-V diagram, and this area can be above, below, or intersecting the zero work axis, leading to positive, negative, or zero net work done. Choice A is incorrect because Wnet is not always positive; it depends on the specific path taken on the P-V diagram. Choice B is incorrect as Wnet is not always negative; it varies based on the enclosed area. Choice D is incorrect because Wnet is not necessarily equal to the total heat transferred into the system; it depends on the specifics of the cycle and is not a direct relationship.

4. The Reynolds number (Re) is a dimensionless quantity used to characterize:

• A. Fluid density
• B. Flow regime (laminar vs. turbulent)
• C. Surface tension effects
• D. Buoyancy force magnitude

Correct answer: B

Rationale: The Reynolds number is a dimensionless quantity used to characterize the flow regime, specifically whether it is laminar (smooth) or turbulent (chaotic). It depends on the velocity of the fluid, its characteristic length (such as pipe diameter), and its viscosity. A low Reynolds number indicates laminar flow, while a high Reynolds number suggests turbulence. Choices A, C, and D are incorrect because the Reynolds number is not related to fluid density, surface tension effects, or buoyancy force magnitude.

5. In open-channel flow, a critical property is the free surface, which refers to the:

• A. Interface between the liquid and the container walls
• B. Interface between the liquid and a surrounding gas
• C. Bottom of the channel
• D. Region of highest velocity within the liquid

Correct answer: B

Rationale: The free surface in open-channel flow refers to the interface between the liquid and the surrounding gas, typically the atmosphere. This interface is critical as it determines the boundary between the liquid flow and the open environment. Option A is incorrect as it refers to the liquid-container wall interface, not the free surface. Option C is incorrect because it represents the bottom of the channel, not the free surface. Option D is incorrect as it describes the region of highest velocity within the liquid, not the free surface. Therefore, the correct choice is B.

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