Nokea
When light travels from air into a denser medium like glass, its speed:
- A. Increases
- B. Decreases
- C. Remains constant
- D. Becomes unpredictable
Correct Answer: B
Rationale: When light travels from air into a denser medium like glass, its speed decreases. This is because the higher refractive index of the denser medium causes light to slow down as it propagates through the medium. Choice A is incorrect because the speed of light decreases in a denser medium. Choice C is incorrect because the speed of light changes when it enters a denser medium. Choice D is incorrect because the change in speed is predictable based on the refractive index of the medium.
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Jon walks all the way around a rectangular park that is 1 km 2 km. Which statement is true about Jon's walk?
- A. The displacement of his walk is 3 kilometers, and the distance traveled is 0 kilometers.
- B. The displacement of his walk is 0 kilometers, and the distance traveled is 16 kilometers.
- C. The displacement of his walk is 6 kilometers, and the distance traveled is 0 kilometers.
- D. The displacement of his walk is 0 kilometers, and the distance traveled is 6 kilometers.
Correct Answer: D
Rationale: Jon walks all the way around a rectangular park that is 1 km 2 km, which means he walks a total distance of 6 kilometers (1 km + 2 km + 1 km + 2 km = 6 km). However, the displacement of his walk is 0 kilometers because he starts and ends at the same point after completing the rectangular path around the park. Displacement refers to the change in position from the starting point to the ending point, regardless of the actual distance traveled. Choice A is incorrect because the total distance traveled by Jon is 6 kilometers, not 0 kilometers. Choice B is incorrect as the displacement is not 0 kilometers, and the distance traveled is 6 kilometers, not 16 kilometers. Choice C is incorrect because the displacement is 0 kilometers, and the distance traveled is 6 kilometers, not 0 kilometers.
As the frequency of a sound wave increases, what else is true?
- A. Its wavelength decreases.
- B. Its wavelength increases.
- C. Its amplitude decreases.
- D. Its amplitude increases.
Correct Answer: A
Rationale: The correct answer is A: 'Its wavelength decreases.' The frequency and wavelength of a sound wave are inversely proportional. As the frequency of a sound wave increases (more oscillations per second), its wavelength decreases. This relationship is described by the formula: Speed of Sound = Frequency x Wavelength. Therefore, to maintain the speed of sound constant, when the frequency increases, the wavelength must decrease. Choices B, C, and D are incorrect because an increase in frequency does not lead to an increase in wavelength or changes in amplitude.
Entropy (S) is a thermodynamic property related to the system's disorder. According to the second law of thermodynamics, in a spontaneous process:
- A. The total entropy of the system and surroundings increases.
- B. The total entropy of the system and surroundings decreases.
- C. The total entropy of the system remains constant.
- D. The total entropy of the surroundings increases, while the system's entropy decreases.
Correct Answer: A
Rationale: The second law of thermodynamics asserts that the entropy of an isolated system (or the combined system and surroundings) will always increase in a spontaneous process, reflecting an increase in disorder. Therefore, the correct answer is that the total entropy of the system and surroundings increases. Choice B is incorrect because entropy always tends to increase in a spontaneous process, as dictated by the second law of thermodynamics. Choice C is incorrect as entropy typically increases in natural processes. Choice D is incorrect because the second law of thermodynamics states that the total entropy of the system and surroundings always increases in a spontaneous process.
A pitcher throws a 45-g baseball at a velocity of 42 meters per second. What is the ball's momentum?
- A. 0.189 kgâ‹…m/s
- B. 1.89 kgâ‹…m/s
- C. 1.07 kgâ‹…m/s
- D. 0.93 kgâ‹…m/s
Correct Answer: B
Rationale: Momentum is calculated by multiplying mass (in kg) by velocity (in m/s). The mass of the baseball is 0.045 kg (45 grams converted to kg), and the velocity is 42 m/s. Momentum = 0.045 kg 42 m/s = 1.89 kgâ‹…m/s. Therefore, the correct answer is 1.89 kgâ‹…m/s. Choice A is incorrect as it incorrectly converts the mass from grams to kg. Choice C and D are incorrect due to calculation errors.
Which of the following statements is true about a refrigerator?
- A. It operates on a Carnot cycle and removes heat from a cold reservoir at a lower temperature.
- B. It violates the first law of thermodynamics by creating cold.
- C. It increases the total entropy of the universe.
- D. It operates isothermally at both the hot and cold reservoirs.
Correct Answer: A
Rationale: A refrigerator operates on a Carnot cycle by transferring heat from a cold reservoir to a hot reservoir. Choice A is correct because a refrigerator removes heat from a cold reservoir at a lower temperature. Choice B is incorrect as a refrigerator does not violate the first law of thermodynamics but rather requires work input to transfer heat. Choice C is incorrect as a refrigerator does not increase the total entropy of the universe. Choice D is incorrect because a refrigerator does not operate isothermally at both the hot and cold reservoirs.