Nursing Elites

1. 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.

2. According to the law of conservation of energy, energy:

• A. Can be created or destroyed
• B. Can be created, but not destroyed
• C. Can be destroyed, but not created
• D. Cannot be created or destroyed

Correct answer: D

Rationale: The correct answer is D: 'Cannot be created or destroyed.' The law of conservation of energy states that energy cannot be created or destroyed; it can only be transformed from one form to another. This principle is a fundamental concept in physics and is supported by numerous observations and experiments. Choices A, B, and C are incorrect because they do not align with the law of conservation of energy. Energy is a conserved quantity, meaning its total amount remains constant over time, even though it can change forms.

3. An electromagnet is holding a 1,500-kg car at a height of 25 m above the ground. The magnet then experiences a power outage, and the car falls to the ground. Which of the following is false?

• A. The car had a potential energy of 367.5 kJ.
• B. 367.5 kJ of potential energy is converted to kinetic energy.
• C. The car retains potential energy of 367.5 kJ when it hits the ground.
• D. The car’s potential energy converts to kinetic energy and then to sound energy.

Correct answer: C

Rationale: When the car falls to the ground, its potential energy is converted to kinetic energy as it accelerates downwards. Upon impact with the ground, the car's kinetic energy is dissipated in various forms, such as sound energy, heat, and deformation energy. Therefore, the car does not retain its initial potential energy of 367.5 kJ when it hits the ground. Choice A is true because the potential energy of the car can be calculated as mgh = 1500 kg * 9.8 m/s^2 * 25 m = 367,500 J = 367.5 kJ. Choice B is true because as the car falls, its potential energy is converted to kinetic energy. Choice D is true as the kinetic energy is eventually dissipated into other forms upon impact.

4. The Prandtl number (Pr) is a dimensionless property relating:

• A. Viscosity and thermal diffusivity
• B. Density and pressure
• C. Surface tension and pressure
• D. Reynolds number and flow regime

Correct answer: A

Rationale: The Prandtl number (Pr) is a dimensionless number used to characterize fluid flow. It is the ratio of momentum diffusivity to thermal diffusivity. In simpler terms, it relates the ability of a fluid to conduct heat to its ability to conduct momentum. Therefore, the correct relationship is between viscosity and thermal diffusivity, making choice A the correct answer. Choices B, C, and D are incorrect because they do not represent the properties that the Prandtl number relates.

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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