Statics and Strength of Materials

526 Pages·2010·9.3 MB·English

by  Harold I. Morrow, Robert P. Kokernak

LIST OF SYMBOLS
(cid:9),(cid:10),(cid:11),(cid:12),(cid:13) = angles J = polar moment of inertia
(cid:8) = totalaxial deformation (strain);also,beam k = any constant
deflection L = length
(cid:7) = unitaxial deformation (strain) L = cablelength
C
(cid:6) = shearingstrain m = mass;also,SI length units (meters)
(cid:5) = Poisson’sratio M = moment of a force;also,moment in a beam
(cid:4) = numericalconstant,3.14159 n = number of bolts (couplings);also,number
(cid:3) = radius of curvature of beam of columns
s = tensile,compressive,bearing,or flexure N = angular speed;also,normal force;also,
(bending) stress number ofbays between columns;also,
(cid:2) = shearing,or torsional shearing stress SI units of force and weight (newtons)
a,b,c,d .....x,y,z = distance NA = neutral axis
A,B,C,... = vector,magnitude and direction p = pitch,of threads
A,B,C... = vector,magnitude only;also,point P = axial force;also,power
designation;also,angles q = shear flow
a = coefficient of rolling resistance;also,weld Q = first moment of area for shear stress in
size beams
A = cross-sectional area r = radius of gyration;also,radius of circle
c = maximum radius or distance from neutral axis R = vector resultant,magnitude and direction
to extremity R = radius of circle;also,vector resultant,
d,D = diameter of circle magnitude only
e = numerical constant,2.71828 s = distance along cable
E = modulus of elasticity (Young’s modulus) S = elastic section modulus
f = coefficient of friction t = plate thickness
F = force T = torque;also,cable tension
F.S. = factor of safety T0 = tensionat vertex of cable
g = acceleration of gravity;also,SI mass units V = shear force
(grams) w = uniformly distributed beam or cable loading
G = modulus of rigidity per unit length
h,H = distance;height oftriangle;cables sag from W = weight
support tovertex x,y = any unknowns
I = rectangular moment of inertia x,y = centroidaldistances
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STATICS AND STRENGTH
OF MATERIALS
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STATICS AND STRENGTH
OF MATERIALS
Seventh Edition
H. W. Morrow
Professor Emeritus
Nassau Community College
Garden City, New York
Robert P. Kokernak
Professor Emeritus
Fitchburg State College
Fitchburg, Massachusetts
Prentice Hall
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Library ofCongress Cataloging-in-Publication Data
Morrow,H.W.(Harold W.)
Statics and strength ofmaterials / H.W.Morrow,Robert P.Kokernak.—7th ed.
p.cm.
Includes index.
ISBN-13:978-0-13-503452-1
ISBN-10:0-13-503452-3
1. Strength ofmaterials. 2. Statics. 3. Strength ofmaterials—Problems,exercises,etc.
4. Statics—Problems,exercises,etc. 5. Trigonometry. I. Kokernak,Robert P.II.Title.
TA405.M877 2011
620.1'12—dc22
2009031922
10 9 8 7 6 5 4 3 2 1
ISBN 10: 0-13-503452-3
ISBN 13:978-0-13-503452-1
For James Kokernak and Christine Smith
You don’t choose your family.
They are God’s gift to you,
as you are to them.
—Bishop Desmond Tutu
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PREFACE
The objective of this seventh edition is to cover statics and indicated by CD icons in the margins ofthe text as
strength ofmaterials at an elementary level,where calculus is shown at the bottom left ofthis page.
not required.However,for instructors who use the text to (cid:2) Although there are still more than 975 practice problems
teach in accredited programs in the technologies,sections to accompany this text,approximately 800 appear here
requiring calculus are included.Those sections relate to cen- inprinted form,with the remainder moved to the
troids and moments ofinertia ofplane areas and deflection Companion Website.This was done to accommodate the
ofbeams by integration.Marked with an asterisk in the table new material described earlier,while keeping the book at
ofcontents,they can be omitted without a loss ofcontinuity. a manageable size for students.These problems are at
Statics and Strength ofMaterialsis written for students en- various levels ofdifficulty and offers a good balance in
rolled in the industrial technology or engineering technology the use ofU.S.customary units and the international
curriculum and in university-level courses for nonengineering system ofunits (SI).
majors,such as architecture.It is also useful for self-study and
(cid:2) The new two-color design highlights features throughout
can serve as a reference for courses in materials,materials test-
the book and increases the clarity offigures and line
ing,machine design,and structural design.
drawings.We have also increased the number ofpho-
tographs to help readers develop a better understanding
NEW TO THIS EDITION ofthe relationship between theory and practice.
As with past editions,we have tried to keep this text as reality
based as possible.Toward that end,the following features
ORGANIZATION OF TEXT
have been added to this edition ofthe book.
Care has been taken to present the various topics clearly in a
(cid:2) The introductory section (Section 1.1) has been ex-
simple and direct fashion and to avoid information over-
panded to include examples ofcatastrophic failures.It
load. To that end, more than 200 examples illustrate the
demonstrates to readers how important statics and
principles involved.
strength ofmaterials are in our everyday lives.
Chapters 1 through 9 focus on statics and beginwith a
(cid:2) The number ofone-page Application Sidebars,which review of basic mathematics.Trigonometric formulas and
have proven so popular with students and faculty alike, the component method are employed to solve concurrent
has been increased from 19 to 25.Each sidebar is heavily force problems.A discussion of the resultant and equilib-
illustrated and describes the real-life application ofthe rium ofnonconcurrent forces follows,with special empha-
material being discussed. sis on the theorem of moments.Then the force analysis of
(cid:2) A short subsection describing some recent developments structures and machines,and concurrent and nonconcur-
in materials technology has been added to Section 11.8. rent force systems in space,are presented.The chapters on
This creates an awareness ofthe wide variety ofresearch statics conclude with friction,centers of gravity,centroids,
worldwide,which results in enhanced material proper- and momentofinertia ofareas.
ties and unique applications for existing materials. Strength ofmaterials is covered in Chapters 10 through 18.
(cid:2) A new section (Section 6.8) on cable analysishas been The chapters begin with the study ofstress and strain in axially
added to this edition.Many textbooks,particularly those loaded members. This is followed by discussions of shear
that are not calculus based,ignore this topic,but an in- stresses and strains in torsion members,bending and deflection
creasing use ofcables on structural projects demands ofbeams,combined stress using Mohr’s circle,columns,and
that students have at least a basic understanding ofthe structural connections.
behavior and analysis ofthese elements. The majority of the material in this book was origi-
nally written by H.W.Morrow,who prepared two prelim-
We have also made several format changes to this sev- inary editions for use at Nassau (NY) Community College
enth edition, each aimed at making the book easier for from 1976 to 1979.These were followed by three editions,
students to use. published in 1981, 1993, and 1998 by Prentice Hall.
(cid:2) The book is now accompanied by an animated CD, Subsequent editions represent a joint collaboration be-
which shows worked examples from various topics in the tween Mr.Morrow and R.P.Kokernak of Fitchburg (MA)
text.References to the CD at appropriate points are State College.
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