HESI A2 Physics

HESI A2 Physics Related

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The operating principle of a metal detector relies on:

  • A. The static presence of a permanent magnet
  • B. The electromotive force induced by a changing magnetic field
  • C. The high electrical conductivity of most metals
  • D. The unique thermal signature of metallic objects
Correct Answer: B

Rationale: The correct answer is B. Metal detectors work based on the principle of electromotive force induced by a changing magnetic field. When a metal object comes into contact with the detector's magnetic field, it disrupts the field, inducing a current in the metal that can be detected. This principle allows metal detectors to identify the presence of metallic objects without relying on the static presence of a permanent magnet, the high electrical conductivity of metals, or the thermal signature of the objects. Choice A is incorrect because metal detectors do not rely on a static magnet but on the interaction of metals with a changing magnetic field. Choice C is incorrect because while metals do have high electrical conductivity, this is not the principle underlying metal detectors. Choice D is incorrect because metal detectors do not operate based on the thermal signature of objects, but rather on their interaction with magnetic fields.

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If a force of 12 kg stretches a spring by 3 cm, how far will the spring stretch when a force of 30 kg is applied?

  • A. 6 cm
  • B. 7.5 cm
  • C. 9 cm
  • D. 10.5 cm
Correct Answer: B

Rationale: The extension of a spring is directly proportional to the force applied. In this case, the force increases from 12 kg to 30 kg, which is a 2.5 times increase. Therefore, the extension of the spring will also increase by 2.5 times. Given that the spring stretches 3 cm with a force of 12 kg, multiplying 3 cm by 2.5 gives us the extension of the spring when a force of 30 kg is applied, which equals 7.5 cm. Therefore, the correct answer is 7.5 cm. Choice A, 6 cm, is incorrect because it does not account for the proportional increase in force. Choice C, 9 cm, and Choice D, 10.5 cm, are incorrect as they overestimate the extension of the spring by not considering the direct proportionality between force and extension.

In fluid dynamics, the continuity equation, a fundamental principle, expresses the conservation of:

  • A. Momentum
  • B. Mass
  • C. Energy
  • D. Angular momentum
Correct Answer: B

Rationale: The continuity equation in fluid dynamics is a statement of the conservation of mass, making choice B the correct answer. It states that the mass entering a system must equal the mass leaving the system, assuming no mass is created or destroyed within the system. Conservation of momentum (choice A) is related to Newton's laws of motion and is not directly expressed by the continuity equation. Conservation of energy (choice C) involves different principles like the first law of thermodynamics and is not the focus of the continuity equation. Angular momentum (choice D) is also a different concept related to rotational motion and not described by the continuity equation.

A 50-kg box of iron fishing weights is balanced at the edge of a table. Peter gives it a push, and it falls 2 meters to the floor. Which of the following statements is true?

  • A. Once the box hits the floor, it loses both its kinetic and potential energy.
  • B. The box had kinetic energy only when it was balanced at the edge of the table.
  • C. The box had both kinetic and potential energy after it fell.
  • D. Once the box hits the floor, it loses all its kinetic energy.
Correct Answer: C

Rationale: When the box is balanced at the edge of the table, it has potential energy due to its position above the ground. As Peter gives it a push, and it falls 2 meters to the floor, the box then has both kinetic energy (due to its motion) and potential energy (due to gravity). Therefore, the correct statement is that the box had both kinetic and potential energy after it fell. Option A is incorrect because the box retains its energy forms even after hitting the floor. Option B is incorrect as the box has kinetic energy both before and after falling. Option D is incorrect as the box still possesses kinetic energy even after hitting the floor.

In fluid machinery, pumps are designed to primarily increase the fluid's:

  • A. Pressure
  • B. Velocity only
  • C. Both pressure and velocity
  • D. Neither pressure nor velocity
Correct Answer: A

Rationale: Pumps in fluid machinery are designed to primarily increase the fluid's pressure. This increase in pressure allows the fluid to flow through the system efficiently and overcome resistance. While pumps can also impact the velocity of the fluid to some extent, their main function is to elevate the pressure to facilitate the movement of the fluid within the system. Choice B is incorrect because pumps do not focus solely on increasing velocity. Choice C is incorrect as while pumps can affect velocity, their primary purpose is to boost pressure. Choice D is incorrect as pumps aim to increase either the pressure, velocity, or both.

A circular running track has a circumference of 2,500 meters. What is the radius of the track?

  • A. 1,000 m
  • B. 400 m
  • C. 25 m
  • D. 12 m
Correct Answer: B

Rationale: The radius of a circular track can be calculated using the formula: Circumference = 2 π radius. Given that the circumference of the track is 2,500 m, we can plug this into the formula and solve for the radius: 2,500 = 2 π radius. Dividing both sides by 2π gives: radius = 2,500 / (2 3.1416) ≈ 397.89 m. Therefore, the closest answer is 400 m, making option B the correct choice. Option A (1,000 m) is too large, option C (25 m) is too small, and option D (12 m) is significantly smaller than the calculated radius.

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