HESI A2
HESI A2 Physics
1. An airplane travels 500 miles northeast and then, on the return trip, travels 500 miles southwest. Which of the following is true?
- A. The displacement of the plane is 1,000 miles, and the distance traveled is 0 miles.
- B. The displacement of the plane is 1,000 miles, and the distance traveled is 1,000 miles.
- C. The displacement of the plane is 0 miles, and the distance traveled is 0 miles.
- D. The displacement of the plane is 0 miles, and the distance traveled is 1,000 miles.
Correct answer: D
Rationale: The displacement of an object is the change in position from the starting point to the ending point, regardless of the path taken. In this case, the airplane returns to its original position after traveling 500 miles northeast and then 500 miles southwest. Therefore, the displacement is 0 miles. However, the distance traveled is the total path covered, which is 500 miles northeast plus 500 miles southwest, for a total of 1,000 miles. Choice A is incorrect because the displacement is not the sum of the distances traveled. Choice B is incorrect as it incorrectly states that both the displacement and the distance traveled are 1,000 miles. Choice C is incorrect as it states that both the displacement and the distance traveled are 0 miles, which is not the case.
2. When a car is driven for a long time, the pressure of air in the tires increases. This is best explained by which of the following gas laws?
- A. Boyle's law
- B. Charles' law
- C. Gay-Lussac's law
- D. Dalton's law
Correct answer: C
Rationale: Gay-Lussac's law, also known as the law of pressure-temperature, states that the pressure of a gas is directly proportional to its absolute temperature when the volume is constant. As a car is driven for a long time, the tires heat up due to friction and increased air pressure inside the tires. This results in an increase in temperature, causing the pressure of the air inside the tires to increase according to Gay-Lussac's law. Choices A, B, and D are incorrect. Boyle's law relates pressure and volume, Charles' law relates volume and temperature, and Dalton's law deals with the partial pressures of gases in a mixture.
3. 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.
4. During an isothermal (constant temperature) expansion, what is the work done by the gas on the surroundings?
- A. Positive and equal to the change in internal energy.
- B. Zero.
- C. Negative and equal to the change in internal energy.
- D. Positive and greater than the change in internal energy.
Correct answer: D
Rationale: In an isothermal expansion, the temperature remains constant, meaning there is no change in internal energy. However, the gas still does work on the surroundings as it expands, and this work is positive. Since internal energy does not change, the correct answer is D, 'Positive and greater than the change in internal energy.' Choice A is incorrect because the work done is not equal to the change in internal energy. Choice B is incorrect as work is done during the expansion. Choice C is incorrect since the work done is not negative during an isothermal expansion.
5. In an electrically neutral atom, the number of:
- A. Electrons is equal to protons
- B. Protons is equal to neutrons
- C. Neutrons are always greater than protons
- D. Electrons are always less than protons
Correct answer: A
Rationale: In an electrically neutral atom, the number of electrons is equal to the number of protons. Electrons carry a negative charge, protons carry a positive charge, and neutrons are neutral. Since the atom is electrically neutral, the positive charge of the protons must balance the negative charge of the electrons, making the numbers of electrons and protons equal. Choice B is incorrect because protons are not equal to neutrons in an atom. Choice C is incorrect because neutrons are not always greater than protons, and choice D is incorrect because electrons are not always less than protons in an atom.
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