Nursing Elites

1. Cavitation is a phenomenon observed in fluids when the pressure falls below its:

• A. Boiling point
• B. Density
• C. Freezing point
• D. Vapor pressure

Correct answer: D

Rationale: Cavitation is a phenomenon where vapor bubbles form in a fluid due to pressure dropping below the vapor pressure of the liquid. When this occurs, the bubbles collapse, creating intense shock waves. The pressure falling below the vapor pressure is what triggers cavitation, not the boiling point, density, or freezing point of the fluid. Therefore, the correct answer is 'Vapor pressure,' as it directly relates to the pressure threshold required for cavitation to happen.

2. What is the main difference between a reversible and irreversible process in thermodynamics?

• A. Reversible processes involve heat transfer, while irreversible processes do not.
• B. Reversible processes occur instantaneously, while irreversible processes take time.
• C. Reversible processes can be run in both directions with the same outcome, while irreversible processes cannot.
• D. Reversible processes violate the first law of thermodynamics.

Correct answer: C

Rationale: A reversible process is an idealized process that can be reversed without leaving any change in either the system or the surroundings. In contrast, irreversible processes cannot be reversed and often involve entropy production or dissipation. Choice A is incorrect because both reversible and irreversible processes can involve heat transfer. Choice B is incorrect as the speed of a process does not determine its reversibility. Choice D is incorrect because reversible processes do not violate the first law of thermodynamics; they comply with it by maintaining a balance between energy inputs and outputs. Therefore, the correct answer is C, as it accurately captures the main difference between reversible and irreversible processes in thermodynamics.

3. The specific heat capacity (c) of a material is the amount of heat transfer (Q) required to raise the temperature (ΔT) of a unit mass (m) of the material by one degree (typically Celsius). The relationship between these quantities is described by the equation:

• A. Q = cΔT
• B. Q = mcΔT
• C. Q = c / mΔT
• D. Q = ΔT / mc

Correct answer: A

Rationale: The correct equation relating heat transfer (Q), mass (m), specific heat capacity (c), and change in temperature (ΔT) is Q = mcΔT. This equation states that the heat transfer is equal to the product of the mass, specific heat capacity, and temperature change. Therefore, the correct answer is B, as it correctly represents this relationship. Choices C and D do not correctly represent the relationship between these quantities and are therefore incorrect.

4. A 5-kg block is suspended from a spring, causing the spring to stretch 10 cm from equilibrium. What is the spring constant for this spring?

• A. 4.9 N/cm
• B. 9.8 N/cm
• C. 49 N/cm
• D. 50 N/cm

Correct answer: C

Rationale: The spring constant (k) can be calculated using Hooke's Law formula: F = -kx, where F is the force applied, k is the spring constant, and x is the displacement from equilibrium. In this case, the force applied is equal to the weight of the block, F = mg, where m = mass of the block = 5 kg and g = acceleration due to gravity = 9.8 m/s^2. The displacement x = 10 cm = 0.1 m. Substituting the values, we have: 5 kg * 9.8 m/s^2 = k * 0.1 m. Solving for k gives k = 5 * 9.8 / 0.1 = 49 N/m. Therefore, the spring constant for this spring is 49 N/cm. Choice A (4.9 N/cm) is incorrect because it is one decimal place lower than the correct answer. Choice B (9.8 N/cm) is incorrect as it does not account for the correct calculation based on the given information. Choice D (50 N/cm) is incorrect because it is slightly higher than the accurate value obtained through the calculations.

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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