HESI A2
HESI A2 Physics
1. Longitudinal waves have vibrations that move ___________.
- A. at right angles to the direction of the vibrations
- B. in the direction opposite to that of the wave
- C. in the same direction as the wave
- D. in waves and troughs
Correct answer: C
Rationale: In longitudinal waves, the vibrations of particles occur in the same direction as the wave propagates. This means the particles move back and forth in the direction of the wave, creating compressions and rarefactions along the wave. Therefore, the correct choice is C, in the same direction as the wave. Choice A is incorrect because transverse waves, not longitudinal waves, have vibrations at right angles to the direction of wave propagation. Choice B is incorrect as it describes the motion in transverse waves. Choice D is incorrect as it is an inaccurate representation of how longitudinal waves propagate.
2. Four 5 V batteries are connected in series. What is the total voltage of the circuit?
- A. 5.0 V
- B. 10.0 V
- C. 15.0 V
- D. 20.0 V
Correct answer: D
Rationale: When batteries are connected in series, their voltages add up. Therefore, the total voltage of the circuit with four 5 V batteries connected in series will be 5 V + 5 V + 5 V + 5 V = 20 V. Choices A, B, and C are incorrect because the voltages of the batteries add up in series, resulting in a total of 20 V.
3. When the heat of a reaction is negative, which statement is true?
- A. The products have less energy and are less stable.
- B. The products have more energy and are more stable.
- C. The products have less energy and are more stable.
- D. The products have more energy and are less stable.
Correct answer: C
Rationale: When the heat of a reaction is negative, it indicates that the reaction releases energy in the form of heat. This means that the products have lower energy levels compared to the reactants. Lower energy levels are associated with greater stability in chemical systems. Therefore, when the heat of a reaction is negative, the products are more stable due to having less energy than the reactants. Choice A, stating that the products have less energy and are less stable, is incorrect as lower energy levels imply greater stability. Choice B, stating that the products have more energy and are more stable, is incorrect as lower energy levels lead to higher stability. Choice D, stating that the products have more energy and are less stable, is incorrect as lower energy levels are associated with higher stability.
4. In fluid machinery, pumps are designed to primarily increase the fluid's:
- A. Pressure
- B. Velocity only
- C. Both pressure and velocity
- D. Neither pressure nor velocity
Correct answer: A
Rationale: Pumps in fluid machinery are designed to primarily increase the fluid's pressure. This increase in pressure allows the fluid to flow through the system efficiently and overcome resistance. While pumps can also impact the velocity of the fluid to some extent, their main function is to elevate the pressure to facilitate the movement of the fluid within the system. Choice B is incorrect because pumps do not focus solely on increasing velocity. Choice C is incorrect as while pumps can affect velocity, their primary purpose is to boost pressure. Choice D is incorrect as pumps aim to increase either the pressure, velocity, or both.
5. Psychrometrics is a branch of thermodynamics that deals with the properties of:
- A. Ideal gases.
- B. Magnetic materials.
- C. Mixtures of moist air and water vapor.
- D. Nuclear reactions.
Correct answer: C
Rationale: Psychrometrics is the study of the physical and thermodynamic properties of gas-vapor mixtures, especially mixtures of moist air and water vapor. This branch of thermodynamics focuses on the relationships between temperature, pressure, humidity, and other properties of these mixtures. Choice A, ideal gases, is incorrect because psychrometrics specifically deals with gas-vapor mixtures, not ideal gases. Choice B, magnetic materials, and Choice D, nuclear reactions, are unrelated to psychrometrics and thermodynamics, making them incorrect. Understanding psychrometrics is crucial in fields like heating, ventilation, air conditioning, and refrigeration (HVAC&R) to design systems that effectively control air quality, comfort, and temperature.
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