HESI A2
HESI A2 Physics Quizlet
1. 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.
2. The Reynolds number (Re) is a dimensionless quantity used to characterize:
- A. Fluid density
- B. Flow regime (laminar vs. turbulent)
- C. Surface tension effects
- D. Buoyancy force magnitude
Correct answer: B
Rationale: The Reynolds number is a dimensionless quantity used to characterize the flow regime, specifically whether it is laminar (smooth) or turbulent (chaotic). It depends on the velocity of the fluid, its characteristic length (such as pipe diameter), and its viscosity. A low Reynolds number indicates laminar flow, while a high Reynolds number suggests turbulence. Choices A, C, and D are incorrect because the Reynolds number is not related to fluid density, surface tension effects, or buoyancy force magnitude.
3. Electric motors convert electrical energy primarily into:
- A. Thermal energy
- B. Light
- C. Mechanical energy
- D. Sound waves
Correct answer: C
Rationale: Electric motors convert electrical energy into mechanical energy. When electricity passes through the coils in the motor, it creates a magnetic field that interacts with the field from the permanent magnets, resulting in a force that drives motion. Choice A, 'Thermal energy,' is incorrect as electric motors are designed to minimize heat production. Choice B, 'Light,' is incorrect as electric motors do not produce light as a primary output. Choice D, 'Sound waves,' is incorrect as the primary output of an electric motor is mechanical motion, not sound waves.
4. 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.
5. 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.
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