HESI A2
HESI Exams Quizlet Physics
1. A 60-watt lightbulb is powered by a 110-volt power source. What is the current being drawn?
- A. 0.55 amperes
- B. 1.83 amperes
- C. 50 amperes
- D. 6,600 amperes
Correct answer: A
Rationale: To calculate the current being drawn, use the formula I = P / V, where I is the current, P is the power in watts, and V is the voltage. Substituting the given values, I = 60 / 110 ≈ 0.55 amperes. Therefore, the current being drawn by the 60-watt lightbulb is approximately 0.55 amperes. Choice B, 1.83 amperes, is incorrect as it does not match the calculated value. Choices C and D, 50 amperes and 6,600 amperes, are significantly higher values and do not align with the expected current draw of a 60-watt lightbulb powered by a 110-volt source.
2. 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.
3. An object moves 100 m in 10 s. What is the velocity of the object over this time?
- A. 10 m/s
- B. 90 m/s
- C. 110 m/s
- D. 1,000 m/s
Correct answer: A
Rationale: Velocity is calculated as the displacement divided by the time taken to cover that displacement. In this case, the object moves 100 meters in 10 seconds. Therefore, the velocity is 100 m / 10 s = 10 m/s. Choice B, 90 m/s, is incorrect as it doesn't match the calculated velocity. Choice C, 110 m/s, is incorrect as it is higher than the calculated velocity. Choice D, 1,000 m/s, is incorrect as it is significantly higher than the calculated velocity.
4. The drag force (F_d) experienced by an object moving through a fluid depends on:
- A. Object's shape and size only
- B. Fluid properties and object velocity
- C. Depth of submersion only
- D. Buoyant force acting on the object
Correct answer: B
Rationale: The drag force experienced by an object moving through a fluid depends on multiple factors, including the object's shape, size, velocity, and the fluid's properties such as viscosity and density. Choices A, C, and D are incorrect because drag force is not solely determined by the object's shape and size, depth of submersion, or buoyant force acting on the object. The primary factors affecting drag force are the fluid properties and the object's velocity. Therefore, the correct answer is B.
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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