HESI A2
HESI A2 Physics
1. As a vehicle positioned at the peak of a hill rolls downhill, its potential energy transforms into:
- A. Thermal energy
- B. Neither thermal nor kinetic energy
- C. A combination of thermal and kinetic energy
- D. Kinetic energy
Correct answer: D
Rationale: The correct answer is D: Kinetic energy. Potential energy is converted into kinetic energy as the vehicle moves downhill. Kinetic energy is the energy possessed by a moving object. Thermal energy is not produced in this scenario because the energy transformation is mainly from potential to kinetic energy, not involving heat generation. Choices A, B, and C are incorrect because the primary energy transformation in this scenario is from potential to kinetic energy, not involving thermal energy.
2. Why are boats more buoyant in salt water than in fresh water?
- A. Salt decreases the mass of the boats.
- B. Salt increases the volume of the water.
- C. Salt affects the density of the boats.
- D. Salt increases the density of the water.
Correct answer: D
Rationale: Salt increases the density of water, making saltwater more buoyant than freshwater. The higher density of saltwater provides more lift to a boat, enabling it to float more easily compared to in freshwater. Choice A is incorrect because salt does not affect the mass of the boats. Choice B is incorrect as salt does not increase the volume of water. Choice C is incorrect since salt affects the density of water, not the boats themselves. Therefore, the correct answer is that salt increases the density of the water, resulting in boats being more buoyant in salt water than in fresh water.
3. Which substance would be most affected by a change in temperature?
- A. Liquid nitrogen
- B. Salt crystals
- C. Hydrogen gas
- D. Iron filings
Correct answer: C
Rationale: Hydrogen gas would be most affected by a change in temperature because gases have a greater expansion or contraction in volume with changes in temperature compared to liquids or solids. When the temperature of hydrogen gas increases, its molecules gain kinetic energy and move faster, causing the gas to expand and its volume to increase. Conversely, when the temperature decreases, the gas molecules lose kinetic energy and move slower, leading to a decrease in volume. This property makes hydrogen gas highly sensitive to temperature changes compared to liquid nitrogen, salt crystals, or iron filings. Liquid nitrogen, salt crystals, and iron filings are less affected by temperature changes because their particles are closer together and have lower kinetic energy, resulting in minimal volume changes with temperature fluctuations.
4. A wave in a rope travels at 12 m/s and has a wavelength of 2 m. What is the frequency?
- A. 38.4 Hz
- B. 6 Hz
- C. 4.6 Hz
- D. 3.75 Hz
Correct answer: B
Rationale: The frequency of a wave is calculated using the formula: frequency = speed / wavelength. In this case, the speed of the wave is 12 m/s and the wavelength is 2 m. Therefore, the frequency is calculated as 12 m/s / 2 m = 6 Hz. Choice A (38.4 Hz), Choice C (4.6 Hz), and Choice D (3.75 Hz) are incorrect as they do not result from the correct calculation using the given values.
5. The amount of energy lost in a circuit due to electrical resistance is dissipated in the form of:
- A. Light
- B. Sound
- C. Heat
- D. Mechanical work
Correct answer: C
Rationale: When electrical current flows through a circuit with resistance, energy is lost in the form of heat due to the resistance encountered by the electrons. This dissipation of energy as heat is a common phenomenon in electrical circuits and is known as Joule heating. Therefore, the correct answer is 'Heat.' Light, sound, and mechanical work are not typical forms in which energy is lost due to electrical resistance. Light is not a direct result of energy dissipation in electrical circuits, sound is not a form of energy dissipation in this context, and mechanical work pertains to the application of physical force and not the dissipation of energy due to resistance.
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