Fluid Mechanics Quiz

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Questions and Answers

What defines an ideal fluid?

It flows in a straight line without any disturbances.

It can easily compress and expand.

It has no internal friction and is incompressible. (correct)

It exhibits laminar flow at all times.

In a cylindrical pipe with two different diameters, what is a key principle governing the relationship between flow speeds?

Flow speed decreases with increasing diameter.

Flow speed is constant regardless of diameter changes.

Flow speed is independent of the pipe's material.

Flow speed varies inversely with the cross-sectional area. (correct)

Which situation is a practical application of Bernoulli's equation?

Calculating the temperature of a fluid.

Measuring the density of a liquid.

Analyzing the pressure changes in a gas cylinder.

Determining the lift generated by an airplane wing. (correct)

What does Bernoulli's equation signify about the work done on a unit volume of fluid?

It is equal to the sum of kinetic and potential energy changes. Signup and view all the answers

Given an incompressible fluid with a density of 850 kg/m³ flowing at a rate of 9.5 L/s, how is the mass flow rate calculated?

By multiplying flow rate by the density of the fluid. Signup and view all the answers

What does specific gravity indicate about a substance's density compared to water?

It is a measure of how much more or less dense a substance is than water. Signup and view all the answers

How does pressure change with depth in a fluid according to Pascal's law?

Pressure increases with depth due to the weight of the fluid above. Signup and view all the answers

What is the relationship between gauge pressure and absolute pressure?

Absolute pressure is found by adding atmospheric pressure to gauge pressure. Signup and view all the answers

What causes the apparent loss of weight for objects submerged in a fluid?

Buoyant force exerted by the fluid acts upward against the weight. Signup and view all the answers

When a fluid is compressed, what happens to the pressure throughout the fluid according to Pascal's law?

Pressure is transmitted equally throughout the fluid. Signup and view all the answers

If two objects made of the same material have different volumes, what can be said about their densities?

Their densities will remain the same regardless of their masses. Signup and view all the answers

Considering a manometer tube filled with water and oil, how does the height of the fluid columns relate?

The difference in height relates directly to the specific gravity of the fluids. Signup and view all the answers

What would happen to the tension in the hoisting cable when a solid object is raised from underwater to above water?

Tension would decrease as the object rises, due to buoyancy effects. Signup and view all the answers

Study Notes

Fluid Mechanics

Fluid mechanics is the study of fluids (liquids and gases) and their behavior.

Density

Density (ρ) is a measure of compactness of matter.
ρ = m/V (definition of density)
Specific Gravity is a measure of the density of a substance compared to the density of water.
- If a liquid has a specific gravity of 1.2, it means it is 1.2 times as dense as water.
- Two objects made of the same material have the same density even though they may have different masses and different volumes.

Densities of Common Substances

(Table of densities in kg/m³ for various substances)

Air: 1.20
Ethanol: 0.81 × 10³
Benzene: 0.90 × 10³
Ice: 0.92 × 10³
Water: 1.00 × 10³
Seawater: 1.03 × 10³
Blood: 1.06 × 10³
Iron/Steel: 7.8 × 10³
Brass: 8.6 × 10³
Copper: 8.9 × 10³
Silver: 10.5 × 10³
Lead: 11.3 × 10³
Mercury: 13.6 × 10³
Gold: 19.3 × 10³

Pressure in a Fluid

Pressure in a fluid is a measure of force distribution over an area.
1 pascal (Pa) = 1 N/m²
1 atm = 1.013 × 10⁵ Pa
1.013 bar = 1013 millibar = 14.70 lb/in.²
Atmospheric pressure is the pressure of Earth's atmosphere and varies with weather and elevation.

Pressure, Depth, and Pascal's Law

p = p₀ + ρgh (pressure in a fluid of uniform density)
- p₀ is the pressure at the surface.
- ρ is the density.
- g is the acceleration due to gravity.
- h is the depth.
"The pressure p at the depth h is greater than the pressure p₀ by an amount ρgh."
Pressure applied to an enclosed fluid is transmitted undiminished to every portion of the fluid and walls of the containing vessels.

Gauge, Absolute, and Atmospheric Pressure

Gauge pressure is the pressure of a system above atmospheric pressure (Pabsolute – Patmospheric).
Absolute pressure is the total pressure exerted on a system (Pgauge + Patmospheric).

Example - Manometer

A manometer measures pressure differences.
In a manometer with water and oil, the relationship between the heights of the liquids is: hoil = (Pwater / P oil) × hwater

Buoyancy and Archimedes's Principle

Buoyancy is the apparent loss of weight due to an upward force exerted by the fluid, called the Buoyant Force.
Archimedes's principle states that when a body is completely or partially immersed in a fluid, the fluid exerts an upward force on the body equal to the weight of the fluid displaced by the body.

Fluid Flow

Ideal fluid is incompressible (density cannot change) and no internal friction.
Laminar and Turbulent flow are types of fluid flows.
The continuity equation (A₁v₁ = A₂v₂) describes the relationship between flow speed and cross-sectional area in an incompressible fluid.

Bernoulli's Equation

Bernoulli's equation relates pressure, flow speed, and height for the flow of an ideal, incompressible fluid.
It's useful in plumbing systems, hydroelectric stations, and airplane flight.
- P₁ + ρgy₁ + ½ρv₁² = P₂ + ρgy₂ + ½ρv₂²
- where P is pressure, ρ is density, g is acceleration due to gravity, y is height, and v is velocity
- Static, Dynamic and Hydrostatic pressures are components of Bernoulli's equation.

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Description

Test your understanding of fluid mechanics, focusing on concepts like density, specific gravity, and pressure in fluids. This quiz covers definitions and densities of common substances, which are essential for grasping fluid behavior. Enhance your knowledge in this fundamental area of physics.