Nursing Elites

1. When a fluid encounters a bluff body (e.g., a car), the flow can separate behind the object, creating a region of low pressure. This phenomenon is known as:

• A. Cavitation
• B. Boundary layer separation
• C. Bernoulli effect per se
• D. Drag crisis

Correct answer: B

Rationale: The correct answer is B: Boundary layer separation. Boundary layer separation occurs when the flow of fluid detaches from the surface of a bluff body, leading to a low-pressure region behind the object. This separation creates a wake region with reduced pressure. Choice A, Cavitation, refers to the formation of vapor bubbles in a fluid and is not relevant in this context. Choice C, Bernoulli effect per se, does not specifically describe the phenomenon of flow separation behind a bluff body. Choice D, Drag crisis, is not the term used to describe the creation of a low-pressure region due to flow separation.

2. A 1,000-kg car drives at 10 m/s around a circle with a radius of 50 m. What is the centripetal acceleration of the car?

• A. 2 m/s²
• B. 4 m/s²
• C. 5 m/s²
• D. 10 m/s²

Correct answer: A

Rationale: Centripetal acceleration is calculated using the formula a = v² / r, where v = 10 m/s and r = 50 m. Substituting these values: a = (10 m/s)² / 50 m = 100 / 50 = 2 m/s². Therefore, the correct answer is 2 m/s². Choice B, 4 m/s², is incorrect because it is not the result of the correct calculation. Choice C, 5 m/s², is incorrect as it does not match the calculated centripetal acceleration. Choice D, 10 m/s², is incorrect as it does not reflect the correct calculation based on the given values.

3. Why does potential energy increase as particles approach each other?

• A. Attractive forces increase.
• B. Attractive forces decrease.
• C. Repulsive forces increase.
• D. Repulsive forces decrease.

Correct answer: C

Rationale: The correct answer is C: Repulsive forces increase. As particles approach each other, the distance between them decreases, causing the repulsive forces between the particles to increase. This increase in repulsive forces leads to an increase in potential energy as the particles resist being pushed closer together. Choices A and B are incorrect because attractive forces do not increase or decrease in this scenario. Choice D is incorrect because repulsive forces actually increase as particles get closer, leading to a rise in potential energy.

4. The specific heat capacity of water is about 2 J/g°C. How much energy would you need to heat 1 kilogram of water by 10°C?

• A. 420 J
• B. 4,200 J
• C. 42,000 J
• D. 420,000 J

Correct answer: C

Rationale: The formula to calculate the energy required to heat a substance is Q = m × c × ΔT, where m is the mass, c is the specific heat capacity, and ΔT is the change in temperature. Given that 1 kilogram of water is equal to 1,000 grams, the mass (m) is 1,000 g, the specific heat capacity (c) of water is 4.2 J/g°C (not 2 J/g°C), and the change in temperature (ΔT) is 10°C. Substituting these values into the formula: Q = 1,000 × 4.2 × 10 = 42,000 J. Therefore, the correct energy required to heat 1 kilogram of water by 10°C is 42,000 J. Choices A, B, and D are incorrect as they do not consider the correct specific heat capacity of water or the conversion of mass to grams.

5. In a circuit with three same-size resistors wired in series to a 9-V power supply, producing 1 amp of current, what is the resistance of each resistor?

• A. 9 ohms
• B. 6 ohms
• C. 3 ohms
• D. 1 ohm

Correct answer: C

Rationale: In a series circuit, the total resistance is the sum of the individual resistances. With a total voltage of 9 V and a current of 1 A, we can use Ohm's Law (V = I × R) to find the total resistance: Total resistance = 9 V / 1 A = 9 ohms. Since the resistors are identical and wired in series, the total resistance is evenly divided among the three resistors: Resistance of each resistor = 9 ohms / 3 = 3 ohms. Thus, the resistance of each resistor is 3 ohms. Therefore, the correct answer is 3 ohms. Choice A, 9 ohms, is incorrect because this would be the total resistance of all three resistors combined in series. Choice B, 6 ohms, is incorrect as it does not account for the equal distribution of resistance in a series circuit. Choice D, 1 ohm, is incorrect as it is too low for resistors in series with a total resistance of 9 ohms.

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