HESI A2 Physics

Correct Answer: B

Rationale: The correct answer is B: The bicycle has less kinetic energy than the car. Kinetic energy is calculated as KE = 0.5 * mass * velocity^2. Since both vehicles are traveling at the same speed, the one with greater mass (the car) will have more kinetic energy. The bicycle, being lighter than the car, will have less kinetic energy despite moving at the same speed. Other choices are incorrect because A is false as explained, C is incorrect as the vehicles have different masses, and D is incorrect as both vehicles are in motion, so both have kinetic energy.

Correct Answer: B

Rationale: To determine the stretch of the spring when a 30 kg force is applied, we first calculate the spring constant using Hooke's Law: F = kx. Given F1 = 12 kg and x1 = 3 cm, k = F1/x1 = 12 kg / 0.03 m = 400 N/m. Then, for F2 = 30 kg, x2 = F2 / k = 30 kg / 400 N/m = 0.075 m = 7.5 cm. Therefore, choice B (7.5 cm) is the correct answer. Choices A, C, and D are incorrect as they do not align with the calculated value using Hooke's Law.

Correct Answer: A

Rationale: Surface tension is caused by the cohesive forces between molecules in a fluid, which are the intermolecular forces. These forces create an imbalance at the surface, resulting in the phenomenon of surface tension. Gravitational attraction (B) is not the primary cause of surface tension, viscous dissipation (C) is related to fluid flow resistance, and pressure differentials (D) within the fluid do not directly cause surface tension. Therefore, the correct answer is A.

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 when the box falls, it converts its potential energy (due to its height above the floor) into kinetic energy (due to its motion). As it falls, its potential energy decreases while its kinetic energy increases. Therefore, the box has both kinetic and potential energy after it falls. A is incorrect because the box still has kinetic energy after hitting the floor. B is incorrect because the box gains kinetic energy as it falls. D is incorrect because the box retains some kinetic energy even after hitting the floor.