HESI A2
HESI A2 Physics Quizlet
1. According to the zeroth law of thermodynamics, two systems are in thermal equilibrium if:
- A. They have the same pressure.
- B. They have the same volume.
- C. They have the same temperature.
- D. They are made of the same material.
Correct answer: C
Rationale: The correct answer is C: "They have the same temperature." The zeroth law of thermodynamics states that if two systems are each in thermal equilibrium with a third system, they are also in thermal equilibrium with each other. This implies that they have the same temperature. Choice A is incorrect because pressure is not the determining factor for thermal equilibrium. Choice B is incorrect because volume alone does not dictate thermal equilibrium. Choice D is incorrect as the materials the systems are made of do not determine thermal equilibrium according to the zeroth law of thermodynamics.
2. In the mechanical power equation P = E / t, power is measured in ___________.
- A. ohms
- B. Joules
- C. volts
- D. watts
Correct answer: D
Rationale: In the mechanical power equation P = E / t, power is measured in watts. Watts are the standard unit of power in the International System of Units (SI), named after the Scottish engineer James Watt. Watts are defined as joules per second, reflecting the rate at which energy is transferred or converted. Ohms (choice A) are the unit of electrical resistance, Joules (choice B) are the unit of energy, and volts (choice C) are the unit of electric potential difference. Therefore, the correct answer is watts as it directly relates to power in the given equation.
3. The first law of thermodynamics is a principle of energy conservation. It states that:
- A. Energy can be created or destroyed.
- B. The total entropy of an isolated system always decreases.
- C. Energy can neither be created nor destroyed, only transferred or transformed.
- D. The temperature of a system is directly proportional to its entropy.
Correct answer: C
Rationale: The first law of thermodynamics states that energy cannot be created or destroyed; it can only be transferred or converted from one form to another, ensuring energy conservation in any system. Choice A is incorrect because it goes against the principle of energy conservation. Choice B is incorrect as it refers to the second law of thermodynamics, which states that the total entropy of an isolated system always increases. Choice D is incorrect because the temperature of a system is not directly proportional to its entropy.
4. A rock has a volume of 6 cm3 and a mass of 24 g. What is its density?
- A. 4 g/cm3
- B. 4 cm3/g
- C. 144 g/cm3
- D. 144 cm3/g
Correct answer: A
Rationale: Density is calculated by dividing the mass of an object by its volume. In this case, the mass of the rock is 24 g and its volume is 6 cm3. By dividing 24 g by 6 cm3, we find that the density of the rock is 4 g/cm3. Choice A is the correct answer because density is expressed in units of mass per unit volume (g/cm3). Choice B is incorrect as it represents the reciprocal of density. Choices C and D are significantly higher values and do not match the calculated density of the rock.
5. According to the Law of Universal Gravitation, the gravitational force between two objects is directly proportional to what factor?
- A. the gravitational constant
- B. the distance between them
- C. the product of their masses
- D. the square of the distance between them
Correct answer: C
Rationale: According to the Law of Universal Gravitation, the gravitational force between two objects is directly proportional to the product of their masses. The equation is: F = G × (m₁ × m₂) / r², where F is the gravitational force, G is the gravitational constant, m₁ and m₂ are the masses of the two objects, and r is the distance between them. Choice A is incorrect because the gravitational constant is a constant value. Choice B is incorrect because the distance between the objects affects the strength of the gravitational force inversely proportional to the square of the distance, not directly proportional. Choice D is incorrect as it represents the inverse square law, where the gravitational force decreases with the square of the distance between the objects.
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