What is a fluid?

A substance that deforms continuously under any applied shear stress, no matter how small.

True or False: Gases have definite volume but no definite shape.

False. Gases have neither definite volume nor definite shape and expand to fill their container.

The formula for density is ρ = _____

M/V (mass per unit volume)

What is the standard density of water at 4°C?
A) 50.4 lbm/ft³
B) 62.4 lbm/ft³
C) 74.8 lbm/ft³
D) 81.2 lbm/ft³

B) 62.4 lbm/ft³

How is specific weight related to density?

Specific weight equals density times gravitational acceleration: γ = ρg

What happens to liquid viscosity as temperature increases?

Liquid viscosity decreases with increasing temperature due to reduced intermolecular cohesive forces.

Calculate specific gravity if a fluid's density is 744 kg/m³ and water's density is 1000 kg/m³.

0.744 (SG = 744/1000 = 0.744)

True or False: Newton's law of viscosity states τ = μ(du/dy).

True. Shear stress equals dynamic viscosity times velocity gradient for Newtonian fluids.

Dynamic viscosity units in SI system are _____

Pa·s (Pascal-seconds)

What is the relationship between kinematic and dynamic viscosity?
A) ν = μρ
B) ν = μ/ρ
C) ν = ρ/μ
D) ν = μ + ρ

B) ν = μ/ρ

Why does gas viscosity increase with temperature?

Higher temperature increases molecular momentum transfer between gas layers, increasing internal friction.

Surface tension is defined as force per unit _____

Length

A soap bubble has _____ surfaces, so pressure difference is Δp = 8σ/d.

Two

True or False: Capillary rise is directly proportional to tube diameter.

False. Capillary rise is inversely proportional to tube diameter (h = 4σcosθ/γd).

What causes capillarity in tubes?

Surface tension and relative magnitudes of cohesion and adhesion forces between liquid and tube.

When does boiling occur in terms of vapor pressure?
A) pᵥ <>
B) pᵥ = psurrounding
C) pᵥ > psurrounding
D) pᵥ = 0

B) pᵥ = psurrounding

Cavitation occurs when local pressure drops below _____

Vapor pressure

What does bulk modulus measure?

A fluid's resistance to compression or volumetric deformation under pressure changes.

True or False: Compressibility is the reciprocal of bulk modulus.

True. β = 1/Eᵥ, where β is compressibility and Eᵥ is bulk modulus.

In the ideal gas law pV = mRT, what does R represent?

Specific gas constant (depends on the particular gas and its molecular weight)

A pressure gauge reads 25 psig. If atmospheric pressure is 14.7 psia, what is absolute pressure?

39.7 psia (absolute pressure = gauge pressure + atmospheric pressure)

Which fluid property increases with temperature for both liquids and gases?
A) Density
B) Viscosity
C) Vapor pressure
D) Surface tension

C) Vapor pressure

Mercury has a specific gravity of _____

13.6

True or False: Newtonian fluids show linear relationship between shear stress and shear strain rate.

True. This linear relationship defines Newtonian fluid behavior under Newton's law of viscosity.

What is the contact angle for water in clean glass tubes?

Approximately 0° (complete wetting condition)

For a spherical droplet, pressure difference across surface is Δp = _____

4σ/d

A hydraulic fluid is compressed from 8 ft³ to 7.9 ft³. Calculate volumetric strain.

0.0125 or 1.25% (ΔV/V = 0.1/8 = 0.0125)

What happens to air density when temperature increases at constant pressure?
A) Increases
B) Decreases
C) Stays constant
D) Becomes zero

B) Decreases

True or False: Kinematic viscosity has units of length²/time.

True. Common units are m²/s or ft²/s.

Why are liquids often treated as incompressible in engineering calculations?

Liquids have very high bulk modulus and extremely low compressibility compared to gases.

The universal gas constant Rᵤ equals _____ J/(kmol·K)

8314

Which property determines whether capillary rise or depression occurs?
A) Fluid density
B) Contact angle
C) Tube material
D) Temperature

B) Contact angle

True or False: Surface tension decreases with increasing temperature.

True. Surface tension decreases with temperature and becomes zero at critical temperature.