HESI A2
HESI A2 Physics
1. Which of the following describes a vector quantity?
- A. 5 miles per hour due southwest
- B. 5 miles per hour
- C. 5 miles
- D. None of the above
Correct answer: A
Rationale: A vector quantity is characterized by both magnitude and direction. In the provided options, choice A, '5 miles per hour due southwest,' fits this definition as it includes both the magnitude (5 miles per hour) and the direction (southwest), making it a vector quantity. Choices B and C only provide the magnitude without indicating any direction, hence they do not represent vector quantities.
2. 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.
3. Sublimation is the change in matter from solid to gas or gas to solid without passing through a liquid phase. Outside of the laboratory, which solid provides the best example of this?
- A. Iron
- B. Silver
- C. Salt crystal
- D. Dry ice
Correct answer: D
Rationale: Dry ice (solid carbon dioxide) provides the best example of sublimation outside of the laboratory. When dry ice is exposed to normal atmospheric conditions, it changes directly from a solid to a gas without passing through a liquid phase. This process is commonly observed in everyday situations such as creating 'smoke' or 'fog' effects. Choices A, B, and C (Iron, Silver, and Salt crystal) do not undergo sublimation. Iron and Silver melt and then vaporize, while Salt crystal dissolves in water, and the resulting solution evaporates, which involves a liquid phase.
4. 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.
5. Marilyn is driving to a wedding. She drives 4 miles south before realizing that she left the gift at home. She makes a U-turn, returns home to pick up the gift, and sets out again driving south. This time, she drives 1 mile out of her way to pick up a friend. From there, they continue 5 miles more to the wedding. Which of these statements is true about Marilyn’s trip?
- A. The displacement of her trip is 6 miles, and the distance traveled is 6 miles.
- B. The displacement of her trip is 14 miles, and the distance traveled is 14 miles.
- C. The displacement of her trip is 8 miles, and the distance traveled is 14 miles.
- D. The displacement of her trip is 6 miles, and the distance traveled is 14 miles.
Correct answer: C
Rationale: Marilyn’s displacement is calculated based on her final position relative to the starting point. She drives 1 mile to pick up her friend, then 5 miles more to the wedding, totaling 6 miles after returning to her home. So, the correct displacement is 8 miles south from her starting point (4 miles to the gift + 4 miles return + 1 mile to the friend + 5 miles to the wedding). The total distance traveled is 14 miles (adding all the distances). Choice A is incorrect because it miscalculates the displacement. Choice B is incorrect as it overestimates both the displacement and distance traveled. Choice D is incorrect as it underestimates the displacement.
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