HESI A2
HESI Exams Quizlet Physics
1. Bernoulli's principle for an incompressible, inviscid fluid in steady flow states that the mechanical energy, consisting of:
- A. Pressure (P) only, remains constant along a streamline.
- B. Velocity (v) only, remains constant along a streamline.
- C. P + ½ρv² (total mechanical energy), remains constant along a streamline
- D. Density (ρ) only, remains constant along a streamline.
Correct answer: C
Rationale: Bernoulli's principle states that the sum of pressure energy (P), kinetic energy per unit volume (½ρv²), and potential energy per unit volume remains constant along a streamline in an incompressible, inviscid fluid. This means the total mechanical energy of the fluid is conserved, making Choice C the correct answer. Choices A, B, and D are incorrect because Bernoulli's principle involves the conservation of the total mechanical energy, not just pressure, velocity, or density alone.
2. When a junked car is compacted, which statement is true?
- A. Its mass increases.
- B. Its mass decreases.
- C. Its density increases.
- D. Its density decreases.
Correct answer: C
Rationale: When a junked car is compacted, its volume decreases while its mass remains the same. As a result, the car's density increases because density is mass divided by volume. Choice A is incorrect because the mass of the car remains the same. Choice B is incorrect because the mass does not decrease. Choice D is incorrect because the density increases as the volume decreases, not decreases.
3. Diamagnetism refers to a material's weak:
- A. Attraction to magnetic fields
- B. Repulsion to magnetic fields
- C. Amplification of magnetic fields
- D. Indifference to magnetic fields
Correct answer: B
Rationale: Diamagnetism refers to a material's weak repulsion to magnetic fields. When diamagnetic materials are placed in an external magnetic field, they create an opposing magnetic field, leading to repulsion. This is why choice B, 'Repulsion to magnetic fields,' is the correct answer. Choices A, C, and D are incorrect because diamagnetic materials do not exhibit attraction, amplification, or indifference to magnetic fields.
4. A Carnot cycle is a theoretical ideal heat engine operating between two heat reservoirs at different temperatures. Which of the following statements is NOT true about a Carnot cycle?
- A. The efficiency of a Carnot cycle is solely dependent on the absolute temperatures of the hot and cold reservoirs.
- B. It is a reversible cycle, meaning the process can be run in both directions with the same efficiency.
- C. It operates isothermally at the hot and cold reservoir temperatures.
- D. It is the most efficient heat engine operating between the same two reservoir temperatures.
Correct answer: C
Rationale: The statement that is NOT true is C. Although part of the Carnot cycle operates isothermally, not the entire cycle operates isothermally. The Carnot cycle consists of both isothermal and adiabatic processes. Choice A is incorrect because the efficiency of a Carnot cycle is indeed solely dependent on the absolute temperatures of the hot and cold reservoirs. Choice B is correct as a Carnot cycle is reversible, allowing the process to be run in both directions with the same efficiency. Choice D is also true as the Carnot cycle is the most efficient heat engine operating between the same two reservoir temperatures. Therefore, the correct answer is C.
5. Two balloons with charges of 5 μC each are placed 25 cm apart. What is the magnitude of the resulting repulsive force between them?
- A. 0.18 N
- B. 1.8 N
- C. 10−3 N
- D. 5 × 10−3 N
Correct answer: B
Rationale: To find the repulsive force between the two charges, we use Coulomb's law: F = k(q1 * q2) / r^2. Here, k is the Coulomb constant (8.99 x 10^9 Nm^2/C^2), q1 and q2 are the charges (5 μC each), and r is the distance between the charges (25 cm = 0.25 m). Substituting these values into the formula: F = (8.99 x 10^9 Nm^2/C^2)(5 x 10^-6 C)(5 x 10^-6 C) / (0.25 m)^2. Calculating this gives F = 1.8 N. Therefore, the magnitude of the resulting repulsive force between the two balloons is 1.8 N. Choice A, C, and D are incorrect as they do not correctly calculate the force using Coulomb's law.
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