Solution Manual for Introduction to Fluid
Mechanics new Edition Covering Chapters 1-
13
What is a Fluid? - answers Any substance that tends to flow or continuously deform
when acted on by a shear force
• Liquids and gases
• Air and water
Explain what is meant by the term 'Relative Velocity'. - answers The velocity of a body
in a fluid depends on the motion of the body and the fluid thus the term relative velocity
is usually relative to the fluid but occasionally relative to another object.
Velocity relative to the fluid influences the forces acting on the object
Define Laminar Flow. - answers Smooth parallel layers of fluid
The pathways of the fluid particles don't cross
Explain what Turbulence is and how it is created. - answers As velocity relative to the
fluid increases, flow of the fluid becomes turbulaent (random/swirling)
Turbulent flow under hand / drag over hand
Define Density; provide its symbol/s and unit of measurement. - answers • Density =
mass per unit of volume
• Density ρ (rho) = m / v
• Units = kgm³
List in order of most dense to least dense the following substances: Muscle, Water, Fat,
Air and Bone. - answers 1. Bone 1100 - 1800 kgm³
2. Muscle 1030 - 1090
3. Water 1000
4. Fat 950 - 990
5. Air 1.21
Define Specific Weight; provide its symbol/s and unit of measurement. - answers
Weight per unit of volume
γ = weight/vol [Specific wt γ (gamma) = weight / volume]
What affect would increasing the density and specific weight of a fluid have on the force
exerted by that fluid on another body? - answers ↑ density & specific weight of the fluid
→ ↑ magnitude of forces exerted by the fluid on the object
Viscosity refers to what? - answers Measure of a fluids internal resistance to flow
, Increasing the viscosity of a fluid would result in what occurring? - answers ↑ viscosity
→ ↑ forces by fluid on object
This is not related to density
In what ways do temperature and pressure influence the density and viscosity of fluids?
- answers • ↑ T → ↓ density & ↓ viscosity
• ↑ P → ↑ density & ↑ viscosity
Define Buoyancy. - answers Fluid force that acts vertically upward
Archimedes' Principle states that... - answers The buoyant force acting on an object in a
fluid is equal to the weight of the fluid displaced by the body
Fb = Vdγ
• Fb = buoyant force
• Vd = Volume displaced
• γ = specific weight of fluid
In which direction do buoyant forces always act? - answers Buoyant forces always act
vertically upward
What affect does increasing the density of a fluid have on the buoyant force that fluid is
capable of exerting? - answers ↑ density of fluid → ↑ Fb (the sea vs fresh water)
The Centre of Volume refers to what? - answers Pt about which a body's volume is
equally balanced, through which the buoyancy force acts
Different to COM or CG
What determines whether a body will float or not? - answers Flotation depends on
relationship between buoyancy and weight
When Fb & W are the only two forces
• Fb = W will have equilibrium (static) → Float
• W > Fb → Sink
For most swimmers, floating occurs when? - answers ...
Why don't most people float level with their body parallel to the surface of the water? -
answers ...
What is Drag and in which direction does it usually act? - answers Drag is force caused
by dynamic action of a fluid
Usually resists movement of an object through fluid
From the formula for drag, list and explain the affect these four factors have on the
magnitude of drag force. - answers FD = ½ CDApv2
• FD = drag force
• CD = coefficient of drag (an index of a body's ability to generate fluid resistance)
Mechanics new Edition Covering Chapters 1-
13
What is a Fluid? - answers Any substance that tends to flow or continuously deform
when acted on by a shear force
• Liquids and gases
• Air and water
Explain what is meant by the term 'Relative Velocity'. - answers The velocity of a body
in a fluid depends on the motion of the body and the fluid thus the term relative velocity
is usually relative to the fluid but occasionally relative to another object.
Velocity relative to the fluid influences the forces acting on the object
Define Laminar Flow. - answers Smooth parallel layers of fluid
The pathways of the fluid particles don't cross
Explain what Turbulence is and how it is created. - answers As velocity relative to the
fluid increases, flow of the fluid becomes turbulaent (random/swirling)
Turbulent flow under hand / drag over hand
Define Density; provide its symbol/s and unit of measurement. - answers • Density =
mass per unit of volume
• Density ρ (rho) = m / v
• Units = kgm³
List in order of most dense to least dense the following substances: Muscle, Water, Fat,
Air and Bone. - answers 1. Bone 1100 - 1800 kgm³
2. Muscle 1030 - 1090
3. Water 1000
4. Fat 950 - 990
5. Air 1.21
Define Specific Weight; provide its symbol/s and unit of measurement. - answers
Weight per unit of volume
γ = weight/vol [Specific wt γ (gamma) = weight / volume]
What affect would increasing the density and specific weight of a fluid have on the force
exerted by that fluid on another body? - answers ↑ density & specific weight of the fluid
→ ↑ magnitude of forces exerted by the fluid on the object
Viscosity refers to what? - answers Measure of a fluids internal resistance to flow
, Increasing the viscosity of a fluid would result in what occurring? - answers ↑ viscosity
→ ↑ forces by fluid on object
This is not related to density
In what ways do temperature and pressure influence the density and viscosity of fluids?
- answers • ↑ T → ↓ density & ↓ viscosity
• ↑ P → ↑ density & ↑ viscosity
Define Buoyancy. - answers Fluid force that acts vertically upward
Archimedes' Principle states that... - answers The buoyant force acting on an object in a
fluid is equal to the weight of the fluid displaced by the body
Fb = Vdγ
• Fb = buoyant force
• Vd = Volume displaced
• γ = specific weight of fluid
In which direction do buoyant forces always act? - answers Buoyant forces always act
vertically upward
What affect does increasing the density of a fluid have on the buoyant force that fluid is
capable of exerting? - answers ↑ density of fluid → ↑ Fb (the sea vs fresh water)
The Centre of Volume refers to what? - answers Pt about which a body's volume is
equally balanced, through which the buoyancy force acts
Different to COM or CG
What determines whether a body will float or not? - answers Flotation depends on
relationship between buoyancy and weight
When Fb & W are the only two forces
• Fb = W will have equilibrium (static) → Float
• W > Fb → Sink
For most swimmers, floating occurs when? - answers ...
Why don't most people float level with their body parallel to the surface of the water? -
answers ...
What is Drag and in which direction does it usually act? - answers Drag is force caused
by dynamic action of a fluid
Usually resists movement of an object through fluid
From the formula for drag, list and explain the affect these four factors have on the
magnitude of drag force. - answers FD = ½ CDApv2
• FD = drag force
• CD = coefficient of drag (an index of a body's ability to generate fluid resistance)
