6. Think abouthow to get from the given informationto the final desiredinfomration.Do not
rush this step.Which principlesof physicscanbe appliedto the problem?Which will help getto
the solution?How arethe known and unknownquantitiesrelated?Are ail of the known
quantitiesrelevan! or might someof themnot affect the answer?Which equationsarerelevant
andmay leadto the solutionto the problem?This steprequiresskills developedonly with much
practicein problemsolving.
7. Frequently,the solutioninvolvesmore than one step.Intermediatequantitiesmight haveto be
found first andthenusedto find the fina1answer.Try to mapout a path from the given
informationto the solution.Wheneverpossible,a goodstrategyis to divide a complexproblem
into severalsimplersubproblems.
8. Performalgebraicmanipulationswith algebraicsyrnbols(letters)asfar aspossible.
Substitutingthe numbersin too early hasa way of hiding mistakes.
9. Finatly, ifthe problemrequiresa numericalanswer,substitutethe known numericalquantities,
with their units, irrto the appropriateequation.Leavingout the units is a commonsourceof error.
Writing the units showswhena unit conversionneedsto be done-andalsomay help identi| an
algebramistake.
10. Oncethe solutionis found,don't be in a hurry to move on. Checkthe answeris it reasonable?
Try to think of othetwaysto solvethe sameproblem.Many problemscanbe solvedin several
different ways.Besidesproviding a checkon the answer,finding morethan onemethodof
. solution deepensour rmderstanding
ofthe principlesofphysics anddevelopsproblem-solving
skills that will help solveotherproblems.
Questionsand ExampleProblemsfrom Chapter I
Problem1
The micrometer(1 pm) is often calledthe micron. (a) How manymicronsmakeup 1.0lan?
(b) Wlat fraction of a centimeterequals1.0 pm? (c) How manymicronsarein 1.0 yd?
-l,A.q = lD-0.'')
1Kn' Jo]r.,
1j J . 3'oft
ll.,! - 3.rtl{t
(")
I.o l(m = t-o$ (
<l.b Kno = l,or
i
lD-'Apl
ffi)(3Y-)6')
=).o4.rr
( u) r.o,r^Yr
(+#)(4#)
(.) .r.Dvr:
r,o>rg
(i#)(!#,*)(,#)
Problem2.
The densityof a neutronstaris approxjmately1.0x 1017kg/m3.Expressthis densityin pounds
per cubic inch (b/in').
=u*d'+(ry)(#,A (ffi)'
}.elbs 1'ox1o'\p
)KA=
-r,.t= 3.\8t{t
1nr
If"O*)D,ny%r_=ffi
J'
'" I7n'
_1{t=tr.,n.
l'""
,a l.o,.,3nro0..vr*,o$ q N\Nfrq
)
/'- 3"G biil^rn
r
$ot
I
"*-*a^
W"^AA
Problem3
Earthis approximatelya sphereof radius6.37 x 106m. what are(a) its circumferencein
kilometers,(b) its surfaceareain squarekilometers,and (c) its voiume in cubic kilometers?
-"-
(o) C =)..,,c= A n (a-ztxlobm)(
\ / _#
)
(.) V= '/1n"3- 4/3n(b3'/.to-")'(ff
)'--+
E =6r" /i'K;
V = J.o8{lora K*3
X
Problern 4
A lectureperiod (50 min) is closeto 1 microcentury.(a) How long is a microcenturyin minutes?
(b) Using
_achral
=( approximarion
% difference
) * roox
actual
\
)
find the percentagedifferencefrom the approximation.
=l-p.rp,n^u
(o)Lu**q
(ffix ffi )fftr)w)
A+-
J)arrnlua4
:
SA-Grmm
5 d' {pryr\I1
* 1oo%= - 1"17,