Nursing Elites

1. Fluids can be categorized based on their shear stress-strain rate relationship. An ideal fluid exhibits:

• A. Zero shear stress at any strain rate
• B. Linear relationship between shear stress and strain rate (Newtonian)
• C. Non-linear relationship between shear stress and strain rate (Non-Newtonian)
• D. High dependence of viscosity on temperature

Correct answer: A

Rationale: An ideal fluid, often referred to as an inviscid fluid, is a theoretical concept used in fluid mechanics to simplify calculations. It is characterized by having zero shear stress at any strain rate. In reality, such fluids do not exist, but they serve as a useful starting point for understanding fluid behavior in idealized situations. Choice B is incorrect because a linear relationship between shear stress and strain rate defines a Newtonian fluid, not an ideal fluid. Choice C is incorrect because a non-linear relationship between shear stress and strain rate characterizes Non-Newtonian fluids, not ideal fluids. Choice D is incorrect because the high dependence of viscosity on temperature is a characteristic seen in real fluids and does not define an ideal fluid.

2. Capillarity describes the tendency of fluids to rise or fall in narrow tubes. This phenomenon arises from the interplay of:

• A. Buoyancy and pressure differentials
• B. Density variations and compressibility of the fluid
• C. Viscous dissipation and inertial effects
• D. Surface tension at the liquid-gas interface and intermolecular forces

Correct answer: D

Rationale: Capillarity occurs due to surface tension and intermolecular forces between the liquid and the walls of the narrow tube. These forces cause the liquid to rise or fall depending on the cohesion and adhesion properties. Surface tension at the liquid-gas interface and intermolecular forces are responsible for capillary action, making choice D the correct answer. Choices A, B, and C are incorrect as they do not directly relate to the specific forces involved in capillarity.

3. Why doesn’t a raindrop accelerate as it approaches the ground?

• A. Gravity pulls it down at a constant rate.
• B. Air resistance counteracts the gravitational force.
• C. Its mass decreases, decreasing its speed.
• D. Objects in motion decelerate over distance.

Correct answer: B

Rationale: The correct answer is B. As a raindrop falls, it experiences air resistance which counteracts the gravitational force pulling it down. This balancing of forces prevents the raindrop from accelerating further as it approaches the ground. Choice A is incorrect because while gravity is pulling the raindrop down, air resistance opposes this force. Choice C is incorrect as the mass of the raindrop remains constant during its fall. Choice D is incorrect because objects in motion may decelerate due to various factors, but in this case, the focus is on why the raindrop doesn't accelerate.

4. Which of the following is NOT a mode of heat transfer between a system and its surroundings?

• A. Conduction
• B. Convection
• C. Radiation
• D. Isothermalization

Correct answer: A

Rationale: Isothermalization is not a mode of heat transfer. The three main modes of heat transfer are conduction (through direct contact), convection (through fluid motion), and radiation (through electromagnetic waves). In this question, choice A, conduction, is not a mode of heat transfer between a system and its surroundings. Conduction refers to heat transfer through direct contact between particles, without the movement of the particles themselves. Therefore, A is the correct answer. Choices B, C, and D are incorrect as they represent valid modes of heat transfer.

5. The drag force (F_d) experienced by an object moving through a fluid depends on:

• A. Object's shape and size only
• B. Fluid properties and object velocity
• C. Depth of submersion only
• D. Buoyant force acting on the object

Correct answer: B

Rationale: The drag force experienced by an object moving through a fluid depends on multiple factors, including the object's shape, size, velocity, and the fluid's properties such as viscosity and density. Choices A, C, and D are incorrect because drag force is not solely determined by the object's shape and size, depth of submersion, or buoyant force acting on the object. The primary factors affecting drag force are the fluid properties and the object's velocity. Therefore, the correct answer is B.

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