Nokea
A system undergoes an isobaric process (constant pressure). In this process, the work done (W) by the system is:
- A. Zero, if the volume change (ΔV) is zero.
- B. Positive and equal to the pressure multiplied by the volume change (W = PΔV).
- C. Negative and equal to the pressure multiplied by the volume change.
- D. Independent of the pressure or volume change.
Correct Answer: B
Rationale: In an isobaric process (constant pressure), the work done is given by the formula W = PΔV, where P is the pressure and ΔV is the change in volume. If the volume does not change, the work done is zero, not negative. Choice A is incorrect as it states the work done is zero when the volume change is zero, which is the correct condition for zero work. Choice C is incorrect as it incorrectly suggests that the work done is negative in an isobaric process. Choice D is incorrect as the work done in an isobaric process is indeed dependent on the volume change and pressure.
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A 5-kg block is suspended from a spring, causing the spring to stretch 10 cm from equilibrium. What is the spring constant for this spring?
- A. 4.9 N/cm
- B. 9.8 N/cm
- C. 49 N/cm
- D. 50 N/cm
Correct Answer: C
Rationale: The spring constant (k) can be calculated using Hooke's Law formula: F = -kx, where F is the force applied, k is the spring constant, and x is the displacement from equilibrium. In this case, the force applied is equal to the weight of the block, F = mg, where m = mass of the block = 5 kg and g = acceleration due to gravity = 9.8 m/s^2. The displacement x = 10 cm = 0.1 m. Substituting the values, we have: 5 kg * 9.8 m/s^2 = k * 0.1 m. Solving for k gives k = 5 * 9.8 / 0.1 = 49 N/m. Therefore, the spring constant for this spring is 49 N/cm. Choice A (4.9 N/cm) is incorrect because it is one decimal place lower than the correct answer. Choice B (9.8 N/cm) is incorrect as it does not account for the correct calculation based on the given information. Choice D (50 N/cm) is incorrect because it is slightly higher than the accurate value obtained through the calculations.
Given the four wires described here, which would you expect to have the greatest resistance?
- A. 1 km of American wire gauge 1; diameter 7.35 mm
- B. 1 km of American wire gauge 2; diameter 6.54 mm
- C. 1 km of American wire gauge 3; diameter 5.83 mm
- D. 1 km of American wire gauge 4; diameter 5.19 mm
Correct Answer: D
Rationale: The wire with the greatest resistance is the one with the smallest diameter, as resistance is inversely proportional to cross-sectional area. Gauge 4 with a 5.19 mm diameter has the smallest diameter and, therefore, the greatest resistance. Choice A, B, and C have larger diameters compared to choice D, so they would have lower resistance values.
Which characteristic does a transverse wave not have?
- A. a compression
- B. an amplitude
- C. a frequency
- D. a wavelength
Correct Answer: A
Rationale: A transverse wave does not have a compression because transverse waves move perpendicular to the direction of the oscillation. In a transverse wave, the particles move up and down, causing crests and troughs, without creating compressions. Compressions are characteristic of longitudinal waves where the particles move parallel to the direction of the wave. The other choices (B, C, and D) are characteristics that transverse waves possess: amplitude is the maximum displacement of a wave from its equilibrium position, frequency is the number of complete oscillations a wave makes in a given time, and wavelength is the distance between two consecutive points in a wave that are in the same phase.
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.
Two objects attract each other with a gravitational force of 12 units. If you double the distance between the objects, what is the new force of attraction between the two?
- A. 3 units
- B. 6 units
- C. 24 units
- D. 48 units
Correct Answer: A
Rationale: The gravitational force between two objects is inversely proportional to the square of the distance between them. If the distance is doubled, the force will be reduced to 1/4 of the original force. Therefore, the new force of attraction between the two objects will be 12 units / 4 = 3 units. Choice A is correct because doubling the distance reduces the force to 1/4 of the original value. Choices B, C, and D are incorrect as they do not consider the inverse square relationship between distance and gravitational force.