Nursing Elites

1. A spring has a spring constant of 20 N/m. How much force is needed to compress the spring from 40 cm to 30 cm?

• A. 200 N
• B. 80 N
• C. 5 N
• D. 2 N

Correct answer: D

Rationale: The change in length of the spring is 40 cm - 30 cm = 10 cm = 0.10 m. The force required to compress or stretch a spring is given by Hooke's Law: F = k × x, where F is the force, k is the spring constant (20 N/m in this case), and x is the change in length (0.10 m). Substituting the values into the formula: F = 20 N/m × 0.10 m = 2 N. Therefore, the correct answer is 2 N. Choice A (200 N) is incorrect because it miscalculates the force. Choice B (80 N) is incorrect as it does not apply Hooke's Law correctly. Choice C (5 N) is incorrect as it underestimates the force required.

2. A 5-cm candle is placed 20 cm away from a concave mirror with a focal length of 10 cm. What is the image distance of the candle?

• A. 20 cm
• B. 40 cm
• C. 60 cm
• D. 75 cm

Correct answer: C

Rationale: To find the image distance of the candle, we use the mirror formula: 1/f = 1/do + 1/di, where f is the focal length, do is the object distance, and di is the image distance. In this case, the focal length f = 10 cm and the object distance do = 20 cm. Substituting these values into the formula gives us 1/10 = 1/20 + 1/di. Solving for di, we get di = 60 cm. Therefore, the image distance of the candle is 60 cm. Choice A (20 cm) is incorrect because it represents the object distance, not the image distance. Choice B (40 cm) is incorrect as it does not consider the mirror formula calculation. Choice D (75 cm) is incorrect as it does not match the correct calculation based on the mirror formula.

3. When light travels from air into a denser medium like glass, its speed:

• A. Increases
• B. Decreases
• C. Remains constant
• D. Becomes unpredictable

Correct answer: B

Rationale: When light travels from air into a denser medium like glass, its speed decreases. This is because the higher refractive index of the denser medium causes light to slow down as it propagates through the medium. Choice A is incorrect because the speed of light decreases in a denser medium. Choice C is incorrect because the speed of light changes when it enters a denser medium. Choice D is incorrect because the change in speed is predictable based on the refractive index of the medium.

4. An airplane travels 500 miles northeast and then, on the return trip, travels 500 miles southwest. Which of the following is true?

• A. The displacement of the plane is 1,000 miles, and the distance traveled is 0 miles.
• B. The displacement of the plane is 1,000 miles, and the distance traveled is 1,000 miles.
• C. The displacement of the plane is 0 miles, and the distance traveled is 0 miles.
• D. The displacement of the plane is 0 miles, and the distance traveled is 1,000 miles.

Correct answer: D

Rationale: The displacement of an object is the change in position from the starting point to the ending point, regardless of the path taken. In this case, the airplane returns to its original position after traveling 500 miles northeast and then 500 miles southwest. Therefore, the displacement is 0 miles. However, the distance traveled is the total path covered, which is 500 miles northeast plus 500 miles southwest, for a total of 1,000 miles. Choice A is incorrect because the displacement is not the sum of the distances traveled. Choice B is incorrect as it incorrectly states that both the displacement and the distance traveled are 1,000 miles. Choice C is incorrect as it states that both the displacement and the distance traveled are 0 miles, which is not the case.

5. During an isothermal (constant temperature) expansion, what is the work done by the gas on the surroundings?

• A. Positive and equal to the change in internal energy.
• B. Zero.
• C. Negative and equal to the change in internal energy.
• D. Positive and greater than the change in internal energy.

Correct answer: D

Rationale: In an isothermal expansion, the temperature remains constant, meaning there is no change in internal energy. However, the gas still does work on the surroundings as it expands, and this work is positive. Since internal energy does not change, the correct answer is D, 'Positive and greater than the change in internal energy.' Choice A is incorrect because the work done is not equal to the change in internal energy. Choice B is incorrect as work is done during the expansion. Choice C is incorrect since the work done is not negative during an isothermal expansion.

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