HESI A2 Physics Practice Test

Correct Answer: D

Rationale: The correct answer is D. Electrons complete a cycle 60 times per second in a 60 Hz household alternating current. This is because the frequency of AC refers to the number of complete cycles per second. Electrons moving back and forth create the alternating current flow. A: Incorrect. The power rating of a bulb (in watts) is determined by the voltage and current, not the frequency. B: Incorrect. The current in household circuits is typically much lower than 60 amperes for safety reasons. C: Incorrect. Voltage drop is dependent on the resistance in the wire and the current flowing, not the frequency of the current.

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: B

Rationale: The correct expression for work (W) is W = F x d. Work is defined as the product of the force applied (F) in the direction of motion and the displacement (d) of the object. Multiplying force by displacement gives the total energy transferred to the object. Option A (W = F / d) is incorrect because dividing force by distance does not represent work. Option C (W = d / F) is incorrect as work is not calculated by dividing distance by force. Option D (W = F^2 x d) is incorrect as squaring the force before multiplying it by displacement is not the correct formula for work. The correct formula for work is the product of force and displacement (W = F x d).

Correct Answer: A

Rationale: The Prandtl number (Pr) is defined as the ratio of momentum diffusivity (kinematic viscosity) to thermal diffusivity in a fluid. Therefore, the correct answer is A, viscosity and thermal diffusivity. This is because Pr provides a measure of the relative importance of momentum diffusivity to thermal diffusivity in a fluid flow. Choices B, C, and D are incorrect because they do not directly relate to the definition and concept of the Prandtl number. B relates to the equation of state, C relates to intermolecular forces, and D relates to flow characteristics, none of which are directly linked to the Prandtl number.

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.