HESI A2
HESI A2 Physics Quizlet
1. In a static fluid, pressure (P) at a depth (h) is governed by the hydrostatic equation:
- A. P = ρgh
- B. P = γh
- C. P = μgh
- D. P = bh
Correct answer: A
Rationale: The correct formula for the pressure at a certain depth in a fluid according to the hydrostatic equation is P = ρgh. Here, ρ represents the fluid's density, g is the gravitational acceleration, and h is the depth. This formula shows that pressure increases linearly with the density of the fluid, the acceleration due to gravity, and the depth. Choices B, C, and D are incorrect because they do not accurately represent the relationship between pressure, density, gravitational acceleration, and depth in a static fluid.
2. When two long, parallel wires carry currents in the same direction, the wires will experience a force of:
- A. An unpredictable force depending on wire material
- B. Repulsion
- C. No force
- D. Attraction
Correct answer: D
Rationale: When two wires carry current in the same direction, they create magnetic fields that interact with each other. This interaction results in an attractive force between the wires due to the alignment of their magnetic fields. Choice A is incorrect because the force can be predicted based on the direction of the currents and the magnetic fields produced. Choice B is incorrect because when currents flow in the same direction, they do not repel each other. Choice C is incorrect because there is indeed a force present due to the interaction of magnetic fields, resulting in attraction between the wires.
3. When a fluid flows past a solid object, a thin layer of fluid adheres to the object's surface due to:
- A. Buoyancy
- B. Bernoulli's principle
- C. Boundary layer effect
- D. Surface tension minimization
Correct answer: C
Rationale: The boundary layer effect occurs when a thin layer of fluid near the surface of a solid adheres to it due to viscosity. This layer experiences a velocity gradient as the fluid farther from the surface moves faster, while the fluid closest to the surface is nearly stationary.
4. For steady, incompressible flow through a pipe, the mass flow rate (ṁ) is related to the fluid density (ρ), cross-sectional area (A), and average velocity (v) via the continuity equation:
- A. ṁ cannot be determined without additional information
- B. ṁ = ρvA
- C. Bernoulli's principle is solely applicable here
- D. The equation of state for the specific fluid is required
Correct answer: B
Rationale: The continuity equation for steady, incompressible flow states that the mass flow rate is the product of the fluid's density, velocity, and cross-sectional area. Hence, ṁ = ρvA. Choice A is incorrect because the mass flow rate can be determined using the given formula. Choice C is incorrect as Bernoulli's principle does not directly relate to the mass flow rate calculation. Choice D is incorrect as the equation of state is not needed to calculate the mass flow rate in this scenario.
5. Electric motors convert electrical energy primarily into:
- A. Thermal energy
- B. Light
- C. Mechanical energy
- D. Sound waves
Correct answer: C
Rationale: Electric motors convert electrical energy into mechanical energy. When electricity passes through the coils in the motor, it creates a magnetic field that interacts with the field from the permanent magnets, resulting in a force that drives motion. Choice A, 'Thermal energy,' is incorrect as electric motors are designed to minimize heat production. Choice B, 'Light,' is incorrect as electric motors do not produce light as a primary output. Choice D, 'Sound waves,' is incorrect as the primary output of an electric motor is mechanical motion, not sound waves.
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