HESI A2 Physics Practice Test

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: 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: D

Rationale: To calculate acceleration, you must use the formula: acceleration = change in velocity / change in time. This is because acceleration is the rate of change of velocity with respect to time. By dividing the change in velocity by the change in time, you get the acceleration of the object. This formula is derived from the definition of acceleration as the rate of change of velocity. The other choices are incorrect because they do not follow the fundamental concept of acceleration as the change in velocity over time. Choice A incorrectly suggests dividing time by velocity, choice B incorrectly suggests multiplying velocity by time, and choice C incorrectly suggests finding the difference between time and velocity, none of which accurately calculate acceleration.

Correct Answer: B

Rationale: To calculate the magnitude of the resulting force, we use Coulomb's Law: \(F = k \cdot \frac{{|q_1 \cdot q_2|}}{{r^2}}\), where \(k\) is the electrostatic constant, \(q_1\) and \(q_2\) are the charges, and \(r\) is the distance between them. Plugging in the values, we get \(F = 9 \times 10^9 \cdot \frac{{3 \times 10^{-6} \cdot 2 \times 10^{-6}}}{{(0.3)^2}} = 0.18\) N. Choice B is correct because it correctly calculates the force using Coulomb's Law. Choices A, C, and D are incorrect because they either miscalculate the force or provide unrealistic values that do not align with the physics of electrostatic forces.

Correct Answer: B

Rationale: The correct answer is B: Boundary layer separation. When a fluid encounters a bluff body, such as a car, the flow separates behind the object due to pressure differences, creating a region of low pressure. This separation of the boundary layer results in increased drag on the object. Cavitation (A) is the formation of vapor bubbles due to low pressure, not specific to bluff bodies. The Bernoulli effect (C) refers to the relationship between fluid speed and pressure, not directly related to flow separation. Drag crisis (D) is a sudden decrease in drag experienced by an object at high speeds, not directly related to flow separation behind a bluff body.