# Figure 5-1 (p. ) a

```Characteristics of Fluids
• Solid- densely spaced molecules with large
intermolecular cohesive forces to maintain its shape.
• Liquid-molecules are spaced apart (10-6-10-7mm),
intermolecular forces are smaller, more freedom in
movement.
Fundamentals of Fluid Mechanics, 5/E by Bruce Munson, Donald Young, and Theodore Okiishi
Forces on Surface
Fluid- Deforms continuously when acted on by shearing stress
(tangential force) (force/unit area)
Fundamentals of Fluid Mechanics, 5/E by Bruce Munson, Donald Young, and Theodore Okiishi
Dimensions
•
•
•
•
•
•
Primary Quantities- L, T, M, q
Secondary Quantities- Area, Velocity, Density
Dimensionally homogeneous
Force, F=mass x acceleration = MLT-2
M=FL-1T2
Stress= Force/area= s=MLT-2/L2 =ML-1T-2
g=32.2 ft/s2
d = 16.1t
2
Fundamentals of Fluid Mechanics, 5/E by Bruce Munson, Donald Young, and Theodore Okiishi
Table 1.1 (p. 4)
Dimensions
Associated with Common
Physical Quantities
(continued on next slide)
Fundamentals of Fluid Mechanics, 5/E by Bruce Munson, Donald Young, and Theodore Okiishi
Table 1.1 (p. 4)
continued
Fundamentals of Fluid Mechanics, 5/E by Bruce Munson, Donald Young, and Theodore Okiishi
Units
• British Gravitational System/English system- length (ft), time (s),
force (lb), temp (oF, oR), mass (slug), weight (force due to
gravity=mg), g=32.174 ft/s2, i.e., mass of 1 slug weighs 32.3 lb
under standard gravity.
• International System (SI) or metric system - length (m), time (s),
temp (K, oC), mass (kg), force (N), g=9.81 m/s2 ,
Work done, 1 J = 1 N. m; Power (watt) 1 W= 1 J/s =1 N. m/s
• English Engineering (EE) system- length (ft), time (s), force (lb),
temp (oR), mass (lbm), force (lb), g=9.81 m/s2 ,
Newton’s second law is expressed as F =ma/gc
gc = 32.174 ft/s2; Weight, W= mg/gc
1 slug =32.174 lbm
Fundamentals of Fluid Mechanics, 5/E by Bruce Munson, Donald Young, and Theodore Okiishi
Mass vs. Weight
Fundamentals of Fluid Mechanics, 5/E by Bruce Munson, Donald Young, and Theodore Okiishi
Table 1.2 (p. 7)
Prefixes for SI Units
Fundamentals of Fluid Mechanics, 5/E by Bruce Munson, Donald Young, and Theodore Okiishi
Table 1.3
(back cover)
Conversion Factors from
BG and EE Units to SI
Units
Fundamentals of Fluid Mechanics, 5/E by Bruce Munson, Donald Young, and Theodore Okiishi
Table 1.4
(back cover)
Prefixes for SI Units
Fundamentals of Fluid Mechanics, 5/E by Bruce Munson, Donald Young, and Theodore Okiishi
A tank of water of total mass of 36 kg rests on the floor of an elevator.
Determine the force (in newtons) that the tank exerts on the floor when
the elevator is accelerating upward at 7 ft/s2.
F = ma
F f  oW = m a
F f = m( g  a )
F f = 36kg[9.81m / s 2  (7 ft / s 2 )(0.3048m / ft )

= 430kg.m / s 2 ;430N
Fundamentals of Fluid Mechanics, 5/E by Bruce Munson, Donald Young, and Theodore Okiishi
Analysis of Fluid Behavior
•
•
•
•
•
Newton’s laws of motion
Conservation of mass
First and second laws of thermodynamics
Fluid at rest- fluid statics
Fluid is moving- fluid dynamics
Fundamentals of Fluid Mechanics, 5/E by Bruce Munson, Donald Young, and Theodore Okiishi
Continuum
• Matter is made up of atoms that are widely spaced in
gas phase
• Yet, disregard the atomic nature and view it is a
continuous, homogeneous matter
• Treat properties as point functions and assume property
vary continuously
Fundamentals of Fluid Mechanics, 5/E by Bruce Munson, Donald Young, and Theodore Okiishi
Density
Density, r = mass/unit
volume –Slugs/ft3;
kg/m3
• Specific volume,
• Specific weight=
weight/volume
• Specific Gravity =
density of the
fluid/density of water
v=
1
r
 = rg
SG =
r
r H [email protected] 4C
2
Fundamentals of Fluid Mechanics, 5/E by Bruce Munson, Donald Young, and Theodore Okiishi
Figure 1.1 (p. 10)
Density of water as a function of temperature.
Fundamentals of Fluid Mechanics, 5/E by Bruce Munson, Donald Young, and Theodore Okiishi
Table 1.5 (front cover)
Approximate Physical Properties of Some Common Liquids (BG Units)
Fundamentals of Fluid Mechanics, 5/E by Bruce Munson, Donald Young, and Theodore Okiishi
Table 1.6 (front cover)
Approximate Physical Properties of Some Common Liquids (SI Units)
Fundamentals of Fluid Mechanics, 5/E by Bruce Munson, Donald Young, and Theodore Okiishi
Ideal/Perfect Gas Law
• Gases are highly compressible, gas density
changes with pressure and temperature,
p = rRT
Pressure should be expressed in lb/ft2 (psf) ;
lb/in2 (psi); N/m2 (Pa)
Standard sea-level atmospheric pressure –
14.7 psi; 101.33 kPa
R is the universal gas constant =8.314 kJ/Kmol ;
1.986 Btu /lb mol
Fundamentals of Fluid Mechanics, 5/E by Bruce Munson, Donald Young, and Theodore Okiishi