HESI A2 Physics Practice Test

Correct Answer: A

Rationale: Rationale: An ideal fluid exhibits zero shear stress at any strain rate. This is because an ideal fluid is assumed to have no resistance to flow, resulting in no shear stress being generated regardless of the strain rate. This is a fundamental characteristic of an ideal fluid and distinguishes it from real fluids that exhibit varying levels of shear stress. Summary: - Choice A is correct as an ideal fluid exhibits zero shear stress at any strain rate. - Choice B is incorrect as it describes a Newtonian fluid which has a linear relationship between shear stress and strain rate. - Choice C is incorrect as it describes a Non-Newtonian fluid with a non-linear relationship between shear stress and strain rate. - Choice D is incorrect as it describes the temperature dependence of viscosity, which is not a defining characteristic of an ideal fluid.

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: The correct answer is A because efficiency (η) is defined as the ratio of net work done (Wnet) by the engine to the heat input (Qh) from the hot reservoir. Mathematically, efficiency is calculated as η = Wnet / Qh. This formula reflects the essence of efficiency as the output (work done) divided by the input (heat input). Choice B is incorrect because dividing heat input by net work done does not represent efficiency. Choice C is incorrect as multiplying net work done by heat input does not reflect efficiency either. Choice D is incorrect because taking the average of net work done and heat input is not a valid way to calculate efficiency. Ultimately, the correct formula for efficiency is the ratio of net work done to heat input, making choice A the correct answer.

Correct Answer: C

Rationale: The correct answer is C because in shear thickening behavior, the fluid's viscosity increases with increasing shear rate. As more force is applied, the fluid's particles align in a way that increases resistance to flow, leading to higher viscosity. Choices A and B are incorrect because shear thickening involves a change in viscosity with shear rate. Choice D is incorrect as viscosity in non-Newtonian fluids is influenced by shear rate, not just applied pressure.

Correct Answer: D

Rationale: The correct answer is D: Refraction. Refraction is the phenomenon of light bending as it passes through different mediums, such as a prism. This occurs due to the change in speed of light when transitioning from one medium to another, causing the light to change direction. Reflection (A) is the bouncing back of light off a surface, not bending. Electrical conduction (B) is the movement of electric charges through a material, not related to light behavior. Diffraction (C) is the bending of light around obstacles or through small openings, not specifically related to prisms.