# Fluid Dynamics & Thermodynamics Flashcards

Fluid Dynamics & Thermodynamics Flashcards
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Describe #2 and #4 in the heating curve. 1. 2 and #4 show phase changes. #2 is the phase change between a solid and a liquid and #4 is the phase change between a liquid and a gas.
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Phase Change

When a substance changes from one phase to another

Heat energy is added or removed, but the temperature remains the same

Example: when water freezes to ice, the temperature stays at 0°C

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Converting between Kelvin and °Celsius

Kelvin = °Celsius - 273

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Equation of Continuity

Velocity * area of one side = velocity * area of the other side

Decreasing the area leads to an increase in the velocity of fluids in a pipe (like a garden hose)

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Pascal's Principle

In an enclosed fluid, the full amount of a change in applied pressure is felt equally by all parts of the fluid and the walls of the container

F1 / A1 = F2 / A2

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Find the density of a liquid that measures 18,200 Pa of pressure at a depth of 2.0 meters.

Pressure = density of liquid * gravity * depth

18,200 Pa = density * 9.8 m/s2 * 2.0 m

Density = 929 kg/m3

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Hydrostatic Pressure

Pressure = density of liquid * gravity * depth

Greater depth = greater pressure

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Pressure

Force per unit area (F / A)

Units: atmospheres (atm), millimeters of mercury (mmHg), torr, pounds per square inch (psi)

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Determine the buoyant force on a 15 kg mass with a density of 1.5 kg/m3.

15 kg * 1 m3 / 1.5 kg = 10 m3

Buoyant force = density of displaced fluid * volume of displaced fluid * acceleration due to gravity = 1000 kg/m3 * 10 m3 * 9.8 m/s2 = 98,000 N

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Determine the force required to lift a 0.5 m3 rock in water if it takes 8,000 N to lift on land.

Buoyant force = density of displaced fluid * volume of displaced fluid * acceleration due to gravity = 1000 kg/m3 * 0.5 m3 * 9.8 m/s2 = 4,900 N

8,000 N - 4,900 N = 3,100 N

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Specific Gravity

A number that shows the ratio between two densities: an object and a reference, usually water (density = 1 g/cm3)

If specific gravity > 1, then the object will sink in water

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## Flashcard Content Overview

Fluid dynamics and thermodynamics are branches of physics that deal with behavior. Fluid dynamics, predictably, looks at the behavior of fluids, while thermodynamics looks at the behavior of heat energy. These flashcards review definitions, equations, and practice problems related to these topics.

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Specific Gravity

A number that shows the ratio between two densities: an object and a reference, usually water (density = 1 g/cm3)

If specific gravity > 1, then the object will sink in water

Determine the force required to lift a 0.5 m3 rock in water if it takes 8,000 N to lift on land.

Buoyant force = density of displaced fluid * volume of displaced fluid * acceleration due to gravity = 1000 kg/m3 * 0.5 m3 * 9.8 m/s2 = 4,900 N

8,000 N - 4,900 N = 3,100 N

Determine the buoyant force on a 15 kg mass with a density of 1.5 kg/m3.

15 kg * 1 m3 / 1.5 kg = 10 m3

Buoyant force = density of displaced fluid * volume of displaced fluid * acceleration due to gravity = 1000 kg/m3 * 10 m3 * 9.8 m/s2 = 98,000 N

Pressure

Force per unit area (F / A)

Units: atmospheres (atm), millimeters of mercury (mmHg), torr, pounds per square inch (psi)

Hydrostatic Pressure

Pressure = density of liquid * gravity * depth

Greater depth = greater pressure

Find the density of a liquid that measures 18,200 Pa of pressure at a depth of 2.0 meters.

Pressure = density of liquid * gravity * depth

18,200 Pa = density * 9.8 m/s2 * 2.0 m

Density = 929 kg/m3

Pascal's Principle

In an enclosed fluid, the full amount of a change in applied pressure is felt equally by all parts of the fluid and the walls of the container

F1 / A1 = F2 / A2

Equation of Continuity

Velocity * area of one side = velocity * area of the other side

Decreasing the area leads to an increase in the velocity of fluids in a pipe (like a garden hose)

Converting between Kelvin and °Celsius

Kelvin = °Celsius - 273

Phase Change

When a substance changes from one phase to another

Heat energy is added or removed, but the temperature remains the same

Example: when water freezes to ice, the temperature stays at 0°C

Describe #2 and #4 in the heating curve. 1. 2 and #4 show phase changes. #2 is the phase change between a solid and a liquid and #4 is the phase change between a liquid and a gas.
Specific Heat

A value that represents the amount of heat needed to change 1 kilogram of a specific substance by 1°C

Determine the amount of heat required to raise the temperature of 2 kg of aluminum from 5°C to 50°C. The specific heat of aluminum is 0.921 J/g°C.

Specific heat = heat energy / (mass of substance * change in temperature)

0.921 J/g°C = heat energy / (2000 g * 45°C)

Heat energy = 82,890 J

Determine the amount of heat required to turn 10 g ice into water if the latent heat of fusion is 334 J/g.

Heat = mass * latent heat = 10 g * 334 J/g = 3340 J

Conduction

The movement of heat energy between two objects in direct contact with one another

Convection

The movement of heat energy in a fluid (liquid or gas) caused by the cycling of hot molecules upward and cold molecules downward due to density differences

Natural Convection

The movement of heat energy in fluids due to differences in temperature

The movement of heat energy by electromagnetic waves, such as from the Sun

The tungsten filament in an incandescent lightbulb has a temperature of 2800 K, an emissivity of 0.27, and a surface area of 8.0 * 10-5 m2. Find the amount of heat transfer in watts.

Radiation = Stefan-Boltzmann constant * emissivity * surface area * temperature4 = 5.67 * 10-8 * 0.27 * 8.0 * 10-5 * 28004 = 75.3 J/s = 75.3 watts

A bridge is made from 1 meter pieces of iron. Determine how much the pieces of iron will shrink from the summer (30°C) to winter (-5°C) if the coefficient of expansion is 12 * 10-6/°C.

Change in length = coefficient of linear expansion * original length * change in temperature = 12 * 10-6/°C * 1 m * 35°C = 0.00042 m = 0.42 mm

Relationship between Temperature and Pressure

Gay-Lussac's Law: when the volume is constant, temperature and pressure of a gas are proportional

As pressure decreases, temperature decreases

As pressure increases, temperature increases

A 20 L canister of helium gas at 4.0 atm of pressure holds 1.5 moles of gas. If 0.5 moles are removed and the temperature drops 20 K, find the change in pressure.

(4.0 atm)(20 L) = (1.5 mol)(0.0821 atm L/mol K)T, T = 650 K

650 K - 20 K = 630 K

P(20 L) = (1.0 mol)(0.0821 atm L/mol K)(630 K)

P = 2.6 atm

ΔP = 4.0 - 2.6 = 1.4 atm

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