HESI A2
HESI A2 Physics Quizlet
1. A 120-volt heat lamp draws 25 amps of current. What is the lamp’s resistance?
- A. 96 ohms
- B. 104 ohms
- C. 150 ohms
- D. 4.8 ohms
Correct answer: D
Rationale: To find the resistance of the lamp, we use Ohm’s Law, which states that resistance (R) is equal to voltage (V) divided by current (I), expressed as: R = V / I. Given that the voltage (V) is 120 volts and the current (I) is 25 amps, we substitute these values into the formula: R = 120 V / 25 A = 4.8 ohms. Therefore, the resistance of the lamp is 4.8 ohms. Choice A, 96 ohms, is incorrect as it is not the result of the correct calculation. Choice B, 104 ohms, is incorrect as it does not match the calculated resistance. Choice C, 150 ohms, is incorrect as it is not the correct resistance value obtained through the calculation.
2. A pitcher throws a 45-g baseball at a velocity of 42 meters per second. What is the ball’s momentum?
- A. 0.189 kg⋅m/s
- B. 1.89 kg⋅m/s
- C. 1.07 kg⋅m/s
- D. 0.93 kg⋅m/s
Correct answer: B
Rationale: Momentum is calculated by multiplying mass (in kg) by velocity (in m/s). The mass of the baseball is 0.045 kg (45 grams converted to kg), and the velocity is 42 m/s. Momentum = 0.045 kg × 42 m/s = 1.89 kg⋅m/s. Therefore, the correct answer is 1.89 kg⋅m/s. Choice A is incorrect as it incorrectly converts the mass from grams to kg. Choice C and D are incorrect due to calculation errors.
3. As the frequency of a sound wave increases, what else is true?
- A. Its wavelength decreases.
- B. Its wavelength increases.
- C. Its amplitude decreases.
- D. Its amplitude increases.
Correct answer: A
Rationale: The correct answer is A: 'Its wavelength decreases.' The frequency and wavelength of a sound wave are inversely proportional. As the frequency of a sound wave increases (more oscillations per second), its wavelength decreases. This relationship is described by the formula: Speed of Sound = Frequency x Wavelength. Therefore, to maintain the speed of sound constant, when the frequency increases, the wavelength must decrease. Choices B, C, and D are incorrect because an increase in frequency does not lead to an increase in wavelength or changes in amplitude.
4. At which point on a roller coaster does the car have the greatest potential energy?
- A. The start of the ride
- B. The highest peak
- C. The lowest trough
- D. The end of the ride
Correct answer: B
Rationale: The correct answer is B, the highest peak. At the highest peak of the roller coaster, the car reaches its maximum height above the ground. This point represents the car's greatest potential energy because it has the highest potential to do work due to its elevated position. The potential energy is directly proportional to the height of an object, so the highest point on the roller coaster track corresponds to the car's greatest potential energy. Choices A, C, and D are incorrect because potential energy is highest at the peak due to its elevated position, not at the start of the ride, the lowest trough, or the end of the ride.
5. The Reynolds number (Re) is a dimensionless quantity used to characterize:
- A. Fluid density
- B. Flow regime (laminar vs. turbulent)
- C. Surface tension effects
- D. Buoyancy force magnitude
Correct answer: B
Rationale: The Reynolds number is a dimensionless quantity used to characterize the flow regime, specifically whether it is laminar (smooth) or turbulent (chaotic). It depends on the velocity of the fluid, its characteristic length (such as pipe diameter), and its viscosity. A low Reynolds number indicates laminar flow, while a high Reynolds number suggests turbulence. Choices A, C, and D are incorrect because the Reynolds number is not related to fluid density, surface tension effects, or buoyancy force magnitude.
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