HESI A2
HESI Exams Quizlet Physics
1. An electromagnet is holding a 1,500-kg car at a height of 25 m above the ground. The magnet then experiences a power outage, and the car falls to the ground. Which of the following is false?
- A. The car had a potential energy of 367.5 kJ.
- B. 367.5 kJ of potential energy is converted to kinetic energy.
- C. The car retains potential energy of 367.5 kJ when it hits the ground.
- D. The car’s potential energy converts to kinetic energy and then to sound energy.
Correct answer: C
Rationale: When the car falls to the ground, its potential energy is converted to kinetic energy as it accelerates downwards. Upon impact with the ground, the car's kinetic energy is dissipated in various forms, such as sound energy, heat, and deformation energy. Therefore, the car does not retain its initial potential energy of 367.5 kJ when it hits the ground. Choice A is true because the potential energy of the car can be calculated as mgh = 1500 kg * 9.8 m/s^2 * 25 m = 367,500 J = 367.5 kJ. Choice B is true because as the car falls, its potential energy is converted to kinetic energy. Choice D is true as the kinetic energy is eventually dissipated into other forms upon impact.
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. Which of the following substances has the highest density?
- A. Mist
- B. Water
- C. Steam
- D. Ice
Correct answer: B
Rationale: Water has the highest density among the options provided. Density is a measure of mass per unit volume. In this case, water in its liquid form is denser than mist, steam, and ice. Ice has a lower density than water because its crystalline structure causes it to be less dense. Mist and steam are forms of water vapor, which are much less dense than liquid water. Therefore, the correct answer is water (choice B).
4. 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.
5. A 0-kg block on a table is given a push so that it slides along the table. If the block is accelerated at 6 m/s2, what was the force applied to the block?
- A. 0 N
- B. 3 N
- C. 6 N
- D. The answer cannot be determined from the information given.
Correct answer: A
Rationale: According to Newton's second law of motion, F=ma. Since the block has a mass of 0 kg, the force applied must be 0 N, as no force is needed to move an object with zero mass.
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