HESI A2 Physics Practice Test

Correct Answer: D

Rationale: The surrounding air is NOT considered a part of the system when analyzing a power plant as it acts as the environment outside the system boundary. The system typically includes components directly involved in the energy conversion process, such as the fuel, working fluid, and turbine. The surrounding air, while it may have an impact on the plant's operations, is not a component within the system boundary and does not play a direct role in the energy conversion process. Choices A, B, and C are all integral parts of the power plant system as they are directly involved in the conversion of energy from the fuel to electricity.

Correct Answer: A

Rationale: To find the period, we use the formula: Period = 1 / Frequency. Given the frequency as 25 beats per second, we calculate 1 / 25 = 0.04 seconds. Therefore, the correct answer is A. Choice B (0.25 s) is incorrect as it represents the inverse of the frequency, not the period. Choice C (0.4 s) and D (4 s) are also incorrect as they are not the correct calculations based on the given frequency.

Correct Answer: A

Rationale: To determine the new length when the force is doubled, we can use Hooke's Law: F = kx, where F is the force, k is the spring constant, and x is the extension. First, calculate the spring constant k = F / x = 12 N / 3 cm = 4 N/cm. Then, find the new extension x' when the force is doubled (24 N): x' = F / k = 24 N / 4 N/cm = 6 cm. Therefore, the new length of the spring would be 25 cm + 6 cm = 31 cm (Choice A). The other choices are incorrect because they do not consider the linear relationship between force and extension as described by Hooke's Law.

Correct Answer: B

Rationale: The correct answer is B: Cork. Density is mass per unit volume. Cork is the lightest material among the choices due to its low mass and high volume, resulting in the lowest density. Water (A) has a higher density than cork. Aluminum (C) and steel (D) are metals with higher densities than cork due to their higher mass and lower volume. Cork's low density makes it less dense compared to the other materials.

Correct Answer: A

Rationale: Rationale: 1. Atoms are electrically neutral, meaning they have no overall charge. 2. Electrons are negatively charged, and protons are positively charged. 3. In a neutral atom, the number of protons equals the number of electrons to balance charges. 4. Therefore, in an electrically neutral atom, the number of electrons is equal to the number of protons (Choice A). Summary: - Choice B is incorrect because protons are not always equal to neutrons in an atom. - Choice C is incorrect as the number of neutrons can vary and is not always greater than protons. - Choice D is incorrect as electrons can be equal to or greater than protons in an atom, depending on the element.