HESI A2
HESI Exams Quizlet Physics
1. Capillarity describes the tendency of fluids to rise or fall in narrow tubes. This phenomenon arises from the interplay of:
- A. Buoyancy and pressure differentials
- B. Density variations and compressibility of the fluid
- C. Viscous dissipation and inertial effects
- D. Surface tension at the liquid-gas interface and intermolecular forces
Correct answer: D
Rationale: Capillarity occurs due to surface tension and intermolecular forces between the liquid and the walls of the narrow tube. These forces cause the liquid to rise or fall depending on the cohesion and adhesion properties. Surface tension at the liquid-gas interface and intermolecular forces are responsible for capillary action, making choice D the correct answer. Choices A, B, and C are incorrect as they do not directly relate to the specific forces involved in capillarity.
2. What is the main difference between a reversible and irreversible process in thermodynamics?
- A. Reversible processes involve heat transfer, while irreversible processes do not.
- B. Reversible processes occur instantaneously, while irreversible processes take time.
- C. Reversible processes can be run in both directions with the same outcome, while irreversible processes cannot.
- D. Reversible processes violate the first law of thermodynamics.
Correct answer: C
Rationale: A reversible process is an idealized process that can be reversed without leaving any change in either the system or the surroundings. In contrast, irreversible processes cannot be reversed and often involve entropy production or dissipation. Choice A is incorrect because both reversible and irreversible processes can involve heat transfer. Choice B is incorrect as the speed of a process does not determine its reversibility. Choice D is incorrect because reversible processes do not violate the first law of thermodynamics; they comply with it by maintaining a balance between energy inputs and outputs. Therefore, the correct answer is C, as it accurately captures the main difference between reversible and irreversible processes in thermodynamics.
3. A 5-cm candle is placed 20 cm away from a concave mirror with a focal length of 15 cm. About what is the image height of the candle in the mirror?
- A. 30.5 cm
- B. 15.625 cm
- C. −15 cm
- D. −30.5 cm
Correct answer: B
Rationale: The magnification formula for a mirror is given by M = -f / (f - d), where f is the focal length of the mirror, and d is the object distance from the mirror. Using the mirror equation and magnification formula, the image height is found to be negative because it is inverted. Plugging in the values (f = 15 cm, d = 20 cm) into the formula gives M = -15 / (15 - 20) = -15 / -5 = 3. The negative sign indicates that the image is inverted. The image height is then calculated by multiplying the magnification by the object height: 3 * 5 cm = 15 cm. Therefore, the correct image height is approximately -15 cm. Choice A (30.5 cm) and Choice D (-30.5 cm) are incorrect as they do not consider the inversion of the image. Choice C (-15 cm) is also incorrect because it neglects the negative sign, which indicates the inversion of the image.
4. Which characteristic does a transverse wave not have?
- A. a compression
- B. an amplitude
- C. a frequency
- D. a wavelength
Correct answer: A
Rationale: A transverse wave does not have a compression because transverse waves move perpendicular to the direction of the oscillation. In a transverse wave, the particles move up and down, causing crests and troughs, without creating compressions. Compressions are characteristic of longitudinal waves where the particles move parallel to the direction of the wave. The other choices (B, C, and D) are characteristics that transverse waves possess: amplitude is the maximum displacement of a wave from its equilibrium position, frequency is the number of complete oscillations a wave makes in a given time, and wavelength is the distance between two consecutive points in a wave that are in the same phase.
5. In hydraulic systems, Pascal's principle states that a pressure change applied to a confined incompressible fluid is:
- A. Amplified but loses energy
- B. Transmitted undiminished throughout the fluid
- C. Limited by the container size
- D. Dependent on the fluid type
Correct answer: B
Rationale: Pascal's principle states that when a pressure change is applied to a confined incompressible fluid, the resulting pressure change is transmitted undiminished throughout the fluid. This means that the pressure change will be the same at every point in the fluid, regardless of the container size or the type of fluid used. Therefore, choice B is the correct answer. Choices A, C, and D are incorrect because Pascal's principle specifically emphasizes the transmission of pressure without amplification, limitation by container size, or dependence on the fluid type.
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