Nokea
Bernoulli's principle for an incompressible, inviscid fluid in steady flow states that the mechanical energy, consisting of:
- A. Pressure (P) only, remains constant along a streamline.
- B. Velocity (v) only, remains constant along a streamline.
- C. P + ½Ïv² (total mechanical energy), remains constant along a streamline
- D. Density (Ï) only, remains constant along a streamline.
Correct Answer: C
Rationale: Bernoulli's principle states that the sum of pressure energy (P), kinetic energy per unit volume (½Ïv²), and potential energy per unit volume remains constant along a streamline in an incompressible, inviscid fluid. This means the total mechanical energy of the fluid is conserved, making Choice C the correct answer. Choices A, B, and D are incorrect because Bernoulli's principle involves the conservation of the total mechanical energy, not just pressure, velocity, or density alone.
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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.
What is the electric field inside a hollow conductor with a net charge?
- A. Remains constant
- B. Decreases
- C. Zero
- D. Becomes unpredictable
Correct Answer: C
Rationale: The correct answer is C: Zero. According to Gauss's Law, the electric field inside a hollow conductor (a conductor with no charge inside but a net charge on its surface) is zero. The charges reside on the outer surface of the conductor, causing the electric field inside to cancel out. Choices A, B, and D are incorrect because the electric field inside a hollow conductor with a net charge is not constant, does not decrease, and does not become unpredictable; it is zero due to the distribution of charges on its surface.
Two balloons with charges of 5 μC each are placed 25 cm apart. What is the magnitude of the resulting repulsive force between them?
- A. 0.18 N
- B. 1.8 N
- C. 10−3 N
- D. 5 10−3 N
Correct Answer: B
Rationale: To find the repulsive force between the two charges, we use Coulomb's law: F = k(q1 * q2) / r^2. Here, k is the Coulomb constant (8.99 x 10^9 Nm^2/C^2), q1 and q2 are the charges (5 μC each), and r is the distance between the charges (25 cm = 0.25 m). Substituting these values into the formula: F = (8.99 x 10^9 Nm^2/C^2)(5 x 10^-6 C)(5 x 10^-6 C) / (0.25 m)^2. Calculating this gives F = 1.8 N. Therefore, the magnitude of the resulting repulsive force between the two balloons is 1.8 N. Choice A, C, and D are incorrect as they do not correctly calculate the force using Coulomb's law.
An incandescent lamp consumes 60 Joules of energy per second. What is the power rating of this lamp?
- A. 1 Watt (W)
- B. 60 Watts (W)
- C. 1/60 Joules
- D. Impossible to determine without knowing the voltage
Correct Answer: B
Rationale: Power is defined as energy consumed per unit time. If the lamp consumes 60 Joules of energy per second, the power rating is 60 Watts. Therefore, choice B is correct. Choice A ('1 Watt') is incorrect because the lamp consumes 60 Joules per second, not 1 Joule per second. Choice C ('1/60 Joules') is incorrect as it does not represent the power rating. Choice D ('Impossible to determine without knowing the voltage') is incorrect because power can be calculated using energy consumption per unit time without needing to know the voltage.