HESI A2
HESI A2 Physics
1. 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.
2. How do you determine the velocity of a wave?
- A. Multiply the frequency by the wavelength.
- B. Add the frequency and the wavelength.
- C. Subtract the wavelength from the frequency.
- D. Divide the wavelength by the frequency.
Correct answer: A
Rationale: The velocity of a wave can be determined by multiplying the frequency of the wave by the wavelength. This relationship is given by the formula: velocity = frequency × wavelength. By multiplying the frequency by the wavelength, you can calculate the speed at which the wave is traveling. This formula is derived from the basic wave equation v = f × λ, where v represents velocity, f is frequency, and λ is wavelength. Therefore, to find the velocity of a wave, one must multiply its frequency by its wavelength. Choices B, C, and D are incorrect. Adding, subtracting, or dividing the frequency and wavelength does not yield the correct calculation for wave velocity. The correct formula for determining wave velocity is to multiply the frequency by the wavelength.
3. How might the energy use of an appliance be expressed?
- A. Power = energy × time
- B. Time + energy = power
- C. Energy = power × time
- D. Energy/power = time
Correct answer: C
Rationale: The energy use of an appliance can be expressed using the formula Energy = Power × Time. In this formula, Energy represents the amount of electricity consumed by the appliance, Power indicates the rate at which the appliance uses electricity (measured in watts), and Time represents the duration for which the appliance is being used (measured in hours). By multiplying the power rating of the appliance by the time it is in use, one can calculate the total energy consumed. Option C is the correct choice because it accurately represents the relationship between power, time, and energy. Choices A, B, and D present incorrect representations of the relationship between energy, power, and time, making them wrong answers.
4. 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.
5. 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.
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