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. Four 5 V batteries are connected in series. What is the total voltage of the circuit?

• A. 5.0 V
• B. 10.0 V
• C. 15.0 V
• D. 20.0 V

Correct answer: D

Rationale: When batteries are connected in series, their voltages add up. Therefore, the total voltage of the circuit with four 5 V batteries connected in series will be 5 V + 5 V + 5 V + 5 V = 20 V. Choices A, B, and C are incorrect because the voltages of the batteries add up in series, resulting in a total of 20 V.

3. A circular running track has a circumference of 2,500 meters. What is the radius of the track?

• A. 1,000 m
• B. 400 m
• C. 25 m
• D. 12 m

Correct answer: B

Rationale: The radius of a circular track can be calculated using the formula: Circumference = 2 × π × radius. Given that the circumference of the track is 2,500 m, we can plug this into the formula and solve for the radius: 2,500 = 2 × π × radius. Dividing both sides by 2π gives: radius = 2,500 / (2 × 3.1416) ≈ 397.89 m. Therefore, the closest answer is 400 m, making option B the correct choice. Option A (1,000 m) is too large, option C (25 m) is too small, and option D (12 m) is significantly smaller than the calculated radius.

4. 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.

5. A 780-watt refrigerator is powered by a 120-volt power source. What is the current being drawn?

• A. 660 amperes
• B. 150 amperes
• C. 6.5 amperes
• D. 0.15 amperes

Correct answer: C

Rationale: To calculate the current being drawn by the refrigerator, you can use the formula: Current (I) = Power (P) / Voltage (V). Given that the power of the refrigerator is 780 watts and the voltage is 120 volts, you can plug these values into the formula to find the current: I = 780 watts / 120 volts = 6.5 amperes. Therefore, the current being drawn by the 780-watt refrigerator is 6.5 amperes. Choice A, 660 amperes, is incorrect as it is significantly higher than the correct answer. Choice B, 150 amperes, is also incorrect and too high. Choice D, 0.15 amperes, is incorrect as it is too low. The correct answer is 6.5 amperes.

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