HESI A2
HESI A2 Physics
1. A box is moved by a 15 N force over a distance of 3 m. What is the amount of work that has been done?
- A. 5 W
- B. 5 Nâ‹…m
- C. 45 W
- D. 45 Nâ‹…m
Correct answer: D
Rationale: Work done is calculated using the formula: Work = Force x Distance. In this case, the force applied is 15 N and the distance covered is 3 m. Thus, work done = 15 N x 3 m = 45 Nâ‹…m. Therefore, the correct answer is 45 Nâ‹…m. Choice A (5 W) is incorrect because work is measured in joules (J) or newton-meters (Nâ‹…m), not in watts (W). Choice B (5 Nâ‹…m) is incorrect as it miscalculates the work by not multiplying the force by the distance. Choice C (45 W) is incorrect because work is not measured in watts (W) but in newton-meters (Nâ‹…m).
2. If a force of 12 kg stretches a spring by 3 cm, how far will the spring stretch when a force of 30 kg is applied?
- A. 6 cm
- B. 7.5 cm
- C. 9 cm
- D. 10.5 cm
Correct answer: B
Rationale: The extension of a spring is directly proportional to the force applied. In this case, the force increases from 12 kg to 30 kg, which is a 2.5 times increase. Therefore, the extension of the spring will also increase by 2.5 times. Given that the spring stretches 3 cm with a force of 12 kg, multiplying 3 cm by 2.5 gives us the extension of the spring when a force of 30 kg is applied, which equals 7.5 cm. Therefore, the correct answer is 7.5 cm. Choice A, 6 cm, is incorrect because it does not account for the proportional increase in force. Choice C, 9 cm, and Choice D, 10.5 cm, are incorrect as they overestimate the extension of the spring by not considering the direct proportionality between force and extension.
3. Two 5-ohm resistors are placed in series and wired into a 100-V power supply. What current flows through this circuit?
- A. 2 A
- B. 10 A
- C. 20 A
- D. 50 A
Correct answer: B
Rationale: In a series circuit, the total resistance is the sum of the individual resistances. Therefore, the total resistance in this circuit is 5 ohms + 5 ohms = 10 ohms. Using Ohm's Law (V = I × R), we can find the current (I) by dividing the voltage (V) by the total resistance (R). I = V / R = 100 V / 10 ohms = 10 A. Choice A (2 A) is incorrect because it does not account for the total resistance of the circuit. Choice C (20 A) and Choice D (50 A) are also incorrect as they provide values that are not consistent with the calculations based on the given values in the question.
4. Longitudinal waves have vibrations that move ___________.
- A. at right angles to the direction of the vibrations
- B. in the direction opposite to that of the wave
- C. in the same direction as the wave
- D. in waves and troughs
Correct answer: C
Rationale: In longitudinal waves, the vibrations of particles occur in the same direction as the wave propagates. This means the particles move back and forth in the direction of the wave, creating compressions and rarefactions along the wave. Therefore, the correct choice is C, in the same direction as the wave. Choice A is incorrect because transverse waves, not longitudinal waves, have vibrations at right angles to the direction of wave propagation. Choice B is incorrect as it describes the motion in transverse waves. Choice D is incorrect as it is an inaccurate representation of how longitudinal waves propagate.
5. When the heat of a reaction is negative, which statement is true?
- A. The products have less energy and are less stable.
- B. The products have more energy and are more stable.
- C. The products have less energy and are more stable.
- D. The products have more energy and are less stable.
Correct answer: C
Rationale: When the heat of a reaction is negative, it indicates that the reaction releases energy in the form of heat. This means that the products have lower energy levels compared to the reactants. Lower energy levels are associated with greater stability in chemical systems. Therefore, when the heat of a reaction is negative, the products are more stable due to having less energy than the reactants. Choice A, stating that the products have less energy and are less stable, is incorrect as lower energy levels imply greater stability. Choice B, stating that the products have more energy and are more stable, is incorrect as lower energy levels lead to higher stability. Choice D, stating that the products have more energy and are less stable, is incorrect as lower energy levels are associated with higher stability.
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