HESI A2
HESI A2 Physics Practice Test
1. When a dielectric material is inserted between the plates of a charged capacitor, what will happen to the capacitance?
- A. Increase
- B. Decrease
- C. Remain the same
- D. Become unpredictable
Correct answer: A
Rationale: When a dielectric material is inserted between the plates of a charged capacitor, the capacitance will increase. This is because the presence of a dielectric material reduces the electric field between the plates, allowing more charge to be stored for a given voltage, thus increasing the capacitance. Choice B is incorrect because adding a dielectric material increases capacitance. Choice C is incorrect because capacitance changes when a dielectric is added. Choice D is incorrect because the effect of a dielectric on capacitance is predictable.
2. According to the zeroth law of thermodynamics, two systems are in thermal equilibrium if:
- A. They have the same pressure.
- B. They have the same volume.
- C. They have the same temperature.
- D. They are made of the same material.
Correct answer: C
Rationale: The correct answer is C: "They have the same temperature." The zeroth law of thermodynamics states that if two systems are each in thermal equilibrium with a third system, they are also in thermal equilibrium with each other. This implies that they have the same temperature. Choice A is incorrect because pressure is not the determining factor for thermal equilibrium. Choice B is incorrect because volume alone does not dictate thermal equilibrium. Choice D is incorrect as the materials the systems are made of do not determine thermal equilibrium according to the zeroth law of thermodynamics.
3. An object with a charge of 4 μC is placed 1 meter from another object with a charge of 2 μC. What is the magnitude of the resulting force between the objects?
- A. 0.04 N
- B. 0.072 N
- C. 80 N
- D. 8 × 10−6 N
Correct answer: A
Rationale: To find the magnitude of the resulting force between two charges, we can use Coulomb's law, which states that the force is directly proportional to the product of the charges and inversely proportional to the square of the distance between them. The formula for Coulomb's law is: F = k × (|q1 × q2| / r²), where F is the force, k is the Coulomb constant, q1 and q2 are the charges, and r is the distance between the charges. Substituting the given values into the formula: F = (9 × 10⁹ N·m²/C²) × ((4 × 10⁻⁶ C) × (2 × 10⁻⁶ C) / (1 m)²) = 0.04 N. Therefore, the magnitude of the resulting force between the objects is 0.04 N.
4. When calculating an object’s acceleration, what must you do?
- A. Divide the change in time by the velocity.
- B. Multiply the velocity by the time.
- C. Find the difference between the time and velocity.
- D. Divide the change in velocity by the change in time.
Correct answer: D
Rationale: When calculating an object's acceleration, you must divide the change in velocity by the change in time. Acceleration is defined as the rate of change of velocity with respect to time. By determining the ratio of the change in velocity to the change in time, you can ascertain how quickly the velocity of an object is changing, thereby finding its acceleration. Choice A is incorrect because acceleration is not calculated by dividing time by velocity. Choice B is incorrect as it describes multiplying velocity by time, which does not yield acceleration. Choice C is incorrect as finding the difference between time and velocity is not a method to calculate acceleration.
5. A bicycle and a car are both traveling at a rate of 5 m/s. Which statement is true?
- A. The bicycle has more kinetic energy than the car.
- B. The bicycle has less kinetic energy than the car.
- C. Both vehicles have the same amount of kinetic energy.
- D. Only the car has kinetic energy.
Correct answer: B
Rationale: Kinetic energy is determined by both the mass and the velocity of an object. While both the bicycle and the car are moving at the same velocity (5 m/s), the car has significantly more mass than the bicycle. As a result, the car has more kinetic energy than the bicycle, even though their speeds are identical. Therefore, choice B is correct. Choices A, C, and D are incorrect because they do not consider the influence of mass on kinetic energy. Choice A is incorrect as the car has more kinetic energy due to its greater mass. Choice C is incorrect because the vehicles have different masses. Choice D is incorrect as both the bicycle and the car possess kinetic energy.
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