HESI A2
HESI Exams Quizlet Physics
1. Why doesn’t a raindrop accelerate as it approaches the ground?
- A. Gravity pulls it down at a constant rate.
- B. Air resistance counteracts the gravitational force.
- C. Its mass decreases, decreasing its speed.
- D. Objects in motion decelerate over distance.
Correct answer: B
Rationale: The correct answer is B. As a raindrop falls, it experiences air resistance which counteracts the gravitational force pulling it down. This balancing of forces prevents the raindrop from accelerating further as it approaches the ground. Choice A is incorrect because while gravity is pulling the raindrop down, air resistance opposes this force. Choice C is incorrect as the mass of the raindrop remains constant during its fall. Choice D is incorrect because objects in motion may decelerate due to various factors, but in this case, the focus is on why the raindrop doesn't accelerate.
2. For the core of an electromagnet, a material with high:
- A. Resistivity is ideal
- B. Permeability is preferred
- C. Permittivity is crucial
- D. Dielectric strength is essential
Correct answer: B
Rationale: A material with high permeability is preferred for the core of an electromagnet because it allows magnetic field lines to pass through it easily, enhancing the strength of the magnetic field generated. Choice A is incorrect because high resistivity would impede the flow of current in the coil, reducing the strength of the magnetic field. Choice C is incorrect as permittivity is related to electric fields, not magnetic fields. Choice D is also incorrect because dielectric strength is about insulating materials against breakdown under an electric field, not relevant to enhancing magnetic fields.
3. A 1,000-kg car drives at 10 m/s around a circle with a radius of 50 m. What is the centripetal acceleration of the car?
- A. 2 m/s²
- B. 4 m/s²
- C. 5 m/s²
- D. 10 m/s²
Correct answer: A
Rationale: Centripetal acceleration is calculated using the formula a = v² / r, where v = 10 m/s and r = 50 m. Substituting these values: a = (10 m/s)² / 50 m = 100 / 50 = 2 m/s². Therefore, the correct answer is 2 m/s². Choice B, 4 m/s², is incorrect because it is not the result of the correct calculation. Choice C, 5 m/s², is incorrect as it does not match the calculated centripetal acceleration. Choice D, 10 m/s², is incorrect as it does not reflect the correct calculation based on the given values.
4. How do a scalar quantity and a vector quantity differ?
- A. A scalar quantity has both magnitude and direction, and a vector does not.
- B. A scalar quantity has direction only, and a vector has only magnitude.
- C. A vector has both magnitude and direction, and a scalar quantity has only magnitude.
- D. A vector has only direction, and a scalar quantity has only magnitude.
Correct answer: C
Rationale: The correct answer is C. The main difference between a scalar quantity and a vector quantity lies in the presence of direction. A vector quantity has both magnitude and direction, while a scalar quantity has magnitude only, without any specified direction. Examples of scalar quantities include distance, speed, temperature, and energy, whereas examples of vector quantities include displacement, velocity, force, and acceleration. Choices A, B, and D are incorrect because they incorrectly describe the characteristics of scalar and vector quantities.
5. A 5-cm candle is placed 20 cm away from a concave mirror with a focal length of 15 cm. About what is the image height of the candle in the mirror?
- A. 30.5 cm
- B. 15.625 cm
- C. −15 cm
- D. −30.5 cm
Correct answer: B
Rationale: The magnification formula for a mirror is given by M = -f / (f - d), where f is the focal length of the mirror, and d is the object distance from the mirror. Using the mirror equation and magnification formula, the image height is found to be negative because it is inverted. Plugging in the values (f = 15 cm, d = 20 cm) into the formula gives M = -15 / (15 - 20) = -15 / -5 = 3. The negative sign indicates that the image is inverted. The image height is then calculated by multiplying the magnification by the object height: 3 * 5 cm = 15 cm. Therefore, the correct image height is approximately -15 cm. Choice A (30.5 cm) and Choice D (-30.5 cm) are incorrect as they do not consider the inversion of the image. Choice C (-15 cm) is also incorrect because it neglects the negative sign, which indicates the inversion of the image.
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