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Fluid dynamics is a subfield of fluid mechanics concerned with:
- A. Equilibrium properties of fluids at rest (Fluid Statics)
- B. The motion and behavior of fluids under various conditions
- C. Phase transitions of fluids between liquid, gas, and solid states
- D. Engineering applications of fluids (related but broader than fluid dynamics)
Correct Answer: B
Rationale: Fluid dynamics is the study of fluids in motion and their behavior under different conditions, including how they flow, mix, and interact with their surroundings. It focuses on the dynamic aspects of fluids rather than their static properties when at rest, which is the realm of fluid statics. Phase transitions of fluids between liquid, gas, and solid states are more related to thermodynamics than fluid dynamics. While engineering applications involve fluid dynamics, the field itself is more specialized in studying the movement and behavior of fluids.
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What force was applied to the object that was moved if 100 Nâ‹…m of work is done over 20 m?
- A. 5 N
- B. 80 N
- C. 120 N
- D. 2,000 N
Correct Answer: A
Rationale: Work is calculated using the formula Work = Force x Distance. Given that 100 Nâ‹…m of work is done over 20 m, we can rearrange the formula to solve for Force. Force = Work / Distance. Plugging in the values, we get Force = 100 Nâ‹…m / 20 m = 5 N. Therefore, the force applied to the object that was moved is 5 N.
Choice B (80 N) is incorrect because it doesn't match the calculated force of 5 N. Choice C (120 N) is incorrect as it is higher than the calculated force. Choice D (2,000 N) is incorrect as it is significantly higher than the correct force of 5 N.
What is the net force acting on the car?
- A. 450 N
- B. 700 N
- C. 1,500 N
- D. 6,300 N
Correct Answer: C
Rationale: To determine the net force acting on an object, we need to consider the sum of the forces acting in the same direction and subtract the forces acting in the opposite direction. In this scenario, there is a force of 4,200 N to the right and a force of 2,700 N to the left. By subtracting the leftward force from the rightward force (4,200 N - 2,700 N), we find that the net force acting on the car is 1,500 N to the right. Therefore, choice C, 1,500 N, is the correct answer. Choice A, 450 N, is too small as it does not account for the total forces involved. Choice B, 700 N, is also incorrect as it is not the result of the correct mathematical operation on the given forces. Choice D, 6,300 N, is too large and does not align with the calculation based on the forces provided.
What is the mathematical expression for work (W)?
- A. W = F / d
- B. W = F x d
- C. W = d / F
- D. W = F^2 x d
Correct Answer: B
Rationale: The correct formula for work (W) is given by the equation W = F x d, where F represents force and d represents the displacement in the direction of the force. Work is calculated by multiplying the force applied by the distance over which the force is applied. Choice A (W = F / d) is incorrect as work is not calculated by dividing force by distance. Choice C (W = d / F) is incorrect because work is not calculated by dividing distance by force. Choice D (W = F^2 x d) is incorrect as work is not calculated by squaring the force and then multiplying by distance.
An object has a constant velocity of 50 m/s and travels for 10 s. What is the acceleration of the object?
- A. 0 m/s²
- B. 5 m/s²
- C. 60 m/s²
- D. 500 m/s²
Correct Answer: A
Rationale: The acceleration of an object is defined as the rate of change of its velocity. When an object has a constant velocity, it means there is no change in its speed or direction. In this case, the object maintains a constant velocity of 50 m/s for 10 seconds, which implies that there is no change in velocity. Therefore, the acceleration of the object is 0 m/s² as there is no acceleration or deceleration happening. Choices B, C, and D are incorrect because acceleration is the change in velocity over time, and in this scenario of constant velocity, the acceleration is 0 m/s².
An object with a charge of 3 μC is placed 30 cm from another object with a charge of 2 μC. What is the magnitude of the resulting force between the objects?
- A. 0.6 N
- B. 0.18 N
- C. 180 N
- D. 9 10−12 N
Correct Answer: B
Rationale: To find the magnitude of the resulting force between two charges, we use Coulomb's Law:
F = k (|q1 q2|) / r²
Where:
F is the force
k is Coulomb's constant (8.99 10â¹ N·m²/C²)
q1 and q2 are the charges
r is the distance between the charges
Plugging in the values:
F = (8.99 10â¹) (3 10â»â¶) (2 10â»â¶) / (0.3)² = 0.18 N.
Therefore, the magnitude of the resulting force is 0.18 N.