HESI A2 Physics

Correct Answer: D

Rationale: During an isothermal expansion, the temperature remains constant, so the internal energy of the gas remains the same. As the gas expands, it does work on the surroundings. Work done is given by W = -PΔV, where P is pressure and ΔV is change in volume. Since the gas is doing work on the surroundings, the work done is positive. The work done is greater than the change in internal energy because some of the work is used to overcome the external pressure to expand and only a portion contributes to the change in internal energy. Therefore, choice D is correct. Choices A and C are incorrect because the work done is not equal to the change in internal energy. Choice B is incorrect because work is being done during the expansion.

Correct Answer: D

Rationale: To calculate impulse, we use the formula Impulse = Change in Momentum. First, calculate the initial momentum: initial momentum = 10 kg * 5 m/s = 50 kg⋅m/s. Then, calculate the final momentum: final momentum = 10 kg * 15 m/s = 150 kg⋅m/s. The change in momentum is final momentum - initial momentum = 150 kg⋅m/s - 50 kg⋅m/s = 100 kg⋅m/s. Therefore, the impulse applied to the object is 100 kg⋅m/s. Choice D is correct as it correctly represents the impulse value. Choices A, B, and C are incorrect as they do not accurately reflect the calculated impulse value.

Correct Answer: C

Rationale: The correct answer is C because longitudinal waves have vibrations that move in the same direction as the wave propagation. In a longitudinal wave, the particles oscillate parallel to the direction of the wave's movement, creating compressions and rarefactions. Option A is incorrect as vibrations in longitudinal waves are not perpendicular. Option B is incorrect because vibrations do not move in the opposite direction of the wave. Option D is incorrect as waves and troughs are not relevant to the direction of vibrations in longitudinal waves.

Correct Answer: C

Rationale: The correct answer is C because psychrometrics specifically deals with the properties of mixtures of moist air and water vapor. It focuses on the study of air-water vapor mixtures and their interactions, such as humidity, temperature, and moisture content. Choice A (Ideal gases) is incorrect because psychrometrics goes beyond the behavior of ideal gases. Choice B (Magnetic materials) is incorrect as it is unrelated to the study of air-water vapor mixtures. Choice D (Nuclear reactions) is also incorrect as it pertains to nuclear physics, not the properties of air-water vapor mixtures. In summary, the correct answer C aligns with the specific focus of psychrometrics on moist air and water vapor properties, making it the most appropriate choice.

Correct Answer: C

Rationale: Step 1: Energy consumption is typically measured in kilowatt-hours. Step 2: Power (in watts) is the rate at which energy is used. Step 3: Energy = Power x Time, as energy consumed is the product of power and time. Step 4: Therefore, the correct expression is Energy = Power x Time (Choice C). Summary: - Choice A is incorrect because power is the rate of energy consumption, not the total energy used. - Choice B is incorrect as it incorrectly combines time and energy without considering the power. - Choice D is incorrect as it rearranges the formula incorrectly, dividing energy by power instead of multiplying.