HESI A2 Physics

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.

Correct Answer: B

Rationale: The correct answer is B: The electromotive force induced by a changing magnetic field. Metal detectors work based on electromagnetic induction where a changing magnetic field induces an electric current in conductive materials like metals. This current generates a secondary magnetic field that is detected by the metal detector. This principle allows metal detectors to identify the presence of metal objects. A: The static presence of a permanent magnet is incorrect because metal detectors do not rely on the static presence of a permanent magnet but rather on inducing electric currents in metals. C: The high electrical conductivity of most metals is incorrect because while it is true that metals are good conductors of electricity, the principle behind metal detectors is based on electromagnetic induction, not on electrical conductivity. D: The unique thermal signature of metallic objects is incorrect because metal detectors do not detect metals based on their thermal properties but rather on the interaction of metals with changing magnetic fields.

Correct Answer: B

Rationale: The correct answer is B: F_b = W_d, the weight of the fluid displaced by the object. This is because the buoyant force acting on an object submerged in a fluid is equal to the weight of the fluid displaced by the object, as stated by Archimedes' principle. When an object is submerged, it displaces a volume of fluid equal to its own volume. The weight of this displaced fluid exerts an upward force on the object, which is the buoyant force. Choices A, C, and D are incorrect because the buoyant force is not equal to the object's weight, the density of the fluid, or the object's volume. The correct answer is based on the principle of fluid displacement and buoyancy.

Correct Answer: C

Rationale: Step 1: A negative heat of reaction indicates that energy is released during the reaction. Step 2: Since energy is released, the products have lower energy compared to the reactants. Step 3: Lower energy in products means they are more stable. Therefore, the correct answer is C: The products have less energy and are more stable. Summary: A: Incorrect. Products have lower energy and are more stable, not less stable. B: Incorrect. Products have lower energy and are more stable, not more stable. D: Incorrect. Products have lower energy and are more stable, not less stable.

Correct Answer: C

Rationale: Failed to generate a rationale after 5 retries.