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. A 2,000-kg car travels at 15 m/s. For a 1,500-kg car traveling at 15 m/s to generate the same momentum, what would need to happen?
- A. It would need to accelerate to 20 m/s.
- B. It would need to add 500 kg in mass.
- C. Both A and B
- D. Either A or B
Correct answer: A
Rationale: Momentum is calculated as the product of mass and velocity. Since momentum is conserved in the absence of external forces, for the 1,500-kg car to generate the same momentum as the 2,000-kg car at 15 m/s, it would need to increase its velocity to compensate for the difference in mass. Accelerating to 20 m/s would achieve this without needing to change the mass of the car. Choice B is incorrect because adding mass is not necessary to match momentum in this scenario.
3. When a car is driven for a long time, the pressure of air in the tires increases. This is best explained by which of the following gas laws?
- A. Boyle's law
- B. Charles' law
- C. Gay-Lussac's law
- D. Dalton's law
Correct answer: C
Rationale: Gay-Lussac's law, also known as the law of pressure-temperature, states that the pressure of a gas is directly proportional to its absolute temperature when the volume is constant. As a car is driven for a long time, the tires heat up due to friction and increased air pressure inside the tires. This results in an increase in temperature, causing the pressure of the air inside the tires to increase according to Gay-Lussac's law. Choices A, B, and D are incorrect. Boyle's law relates pressure and volume, Charles' law relates volume and temperature, and Dalton's law deals with the partial pressures of gases in a mixture.
4. A constant force is exerted on a stationary object. In this scenario, work is:
- A. Performed
- B. Not performed
- C. Partially performed
- D. Inconclusive without further information
Correct answer: B
Rationale: Work is only done when a force causes displacement. Since the object is stationary, no displacement occurs, and therefore, no work is performed. Choice A is incorrect because work requires both force and displacement. Choice C is incorrect as there is no partial work - work is either done or not done. Choice D is incorrect as the scenario provided is clear - the object is stationary, so no work is being performed.
5. An incandescent lamp consumes 60 Joules of energy per second. What is the power rating of this lamp?
- A. 1 Watt (W)
- B. 60 Watts (W)
- C. 1/60 Joules
- D. Impossible to determine without knowing the voltage
Correct answer: B
Rationale: Power is defined as energy consumed per unit time. If the lamp consumes 60 Joules of energy per second, the power rating is 60 Watts. Therefore, choice B is correct. Choice A ('1 Watt') is incorrect because the lamp consumes 60 Joules per second, not 1 Joule per second. Choice C ('1/60 Joules') is incorrect as it does not represent the power rating. Choice D ('Impossible to determine without knowing the voltage') is incorrect because power can be calculated using energy consumption per unit time without needing to know the voltage.
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