HESI A2 Physics

Correct Answer: B

Rationale: The continuity equation in fluid dynamics states that the mass entering a system must equal the mass exiting the system for mass to be conserved. This is why the correct answer is B: Mass. Momentum (A) is related to the motion of fluids, not mass conservation. Energy (C) is related to the total energy of the system, not specifically mass conservation. Angular momentum (D) is related to rotational motion, not mass conservation. Therefore, the correct answer is B.

Correct Answer: A

Rationale: The correct answer is A: Experience a net buoyant force acting upwards. When the specific gravity of an object is greater than 1, it means the object is denser than the reference fluid. According to Archimedes' Principle, a submerged object experiences an upward buoyant force equal to the weight of the fluid it displaces. Since the object is denser than the fluid, it will displace less fluid, resulting in a net buoyant force acting upwards. Choice B is incorrect because a denser object will displace less fluid, leading to an upward buoyant force. Choice C is incorrect because neutrally buoyant objects have an SG equal to that of the reference fluid. Choice D is incorrect because the object's volume is not needed to determine the direction of the buoyant force based on specific gravity alone.

Correct Answer: C

Rationale: The correct answer is C because in a cyclic process, the system returns to its initial state, so the net work done over the entire cycle can be positive, negative, or zero depending on the path taken. If the system undergoes a clockwise cycle on a PV diagram, work is done by the system (positive Wnet). If the cycle is counterclockwise, work is done on the system (negative Wnet). If the cycle is a closed loop, the net work done can be zero. Choices A and B are incorrect because they are too absolute and do not consider the different possibilities in a cyclic process. Choice D is incorrect because the net work done is not necessarily equal to the total heat transferred; it depends on the specific process and path taken.

Correct Answer: D

Rationale: The correct answer is D because salt increases the density of water, making it more buoyant. Higher water density provides greater buoyant force on the boat, allowing it to float more easily. Choices A, B, and C are incorrect as salt does not directly affect the mass of the boat, the volume of water, or the density of the boat itself.

Correct Answer: C

Rationale: To find the image distance using the mirror formula (1/f = 1/v + 1/u), we first need to calculate the object distance (u). Given the object distance (u) is 20 cm, and the focal length (f) is 10 cm, we can substitute these values into the formula to find the image distance (v). Solving for v, we get v = 60 cm. Therefore, the correct answer is C: 60 cm. Choice A (20 cm) is incorrect as the image distance is not equal to the object distance when using a concave mirror. Choice B (40 cm) is incorrect as it does not account for the focal length of the mirror. Choice D (75 cm) is incorrect as it is not the result of the correct calculation using the mirror formula.