~~r ~dl~~ l' 1/1) (f!j) - umd physics · £xr.p3 page 5 of 16 exam i: physics 121 f03 october...
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.Page 3 of 16
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Exam I: Physics 121 F03 James J. GriffinOctober 3, 2003 Physics 2109/Tel.301-405-6118
Exam I, Part I: Multiple Choice
This Part I of Exam I consists of 16 parts worth 6 points each and comprises 80% of thefull exam. For each problem fill in the circle next to the letter of your chosen answer onthe NCS answer sheet using a #2 pencil, making sure that the number of the linecorresponds to the number of the problem you are answering. There is only one correctanswer for each problem, and no subtractions will be made for wrong answers.Use only lines 1 through 16 on the NCS sheet.
d. x/y = Cos ~ 2 (') l.fr ~ .lfr- @ ~)
~ X(t) = Xo + Vo t JJ 'li. ; d.4--S/~/t;g 2. IJ/ ~ (
LL.T e) L ~ L. ..,. ~
L'.
@ !-1" ~ c,..-d cJ dl d
~).I; m d,)11~/AI
~ In e.#k4S IS;e..t"
(Over for Page 4 of 16)
1. Which of the equations below is dimensionally incorrect?Insert the letter of your chosen answer into your liC$' answer sh~.a. v2 = VO2 +2ax -1 (Llr) .I :" l'lr}2 of 2 (i;r~L fdi
b. a = ao + v!t £L( lLooI 'Ir /2',
Ic. v=xlt A 'J L.lra :. "7 + 7'1 ~
1'2.&I
Page 4 of 16
Exam I: Physics 121 F03October 3,2003
James J. GriffinPhysics 2109fTel.301-405-6118
3. Suppose that 2 macrol!:letoerites per century strike each square meter of the surface of some distant moon,and that each a sphere ofrndius 0.3 mrn. Given that a year isabout 3x107 s, how many seconds would it taketo cover the moon's surf~ce with meteorites UD to-a dep!llJJfAfi-C1ll? A ~~-~ 3 -A L (.JL. rr~/-')1f
1. A L 'ttt -D--IJV. /0 .tJ .:f.- ~ --u~r--- -10 3(J'YI ~"Wl.l.4 )rI6A ..,~ Ff1'P"' 6 'l..I'8~- ~.1 (~ "ID-;~3= Z..z X t() ,...
£ J. "&.n1J ~6S (l ~ 1zr,,", (0./"..7;JJ :::(J.2It L~ :: 2Xlo..~~ "Z0- AII..-~/ .At ~ R=~'1Y)tl2 F~ 3x(~-P'<
-71 ---' N- V /".. I-~ ,/}1jZ 'JIM-. 1t~ ~ -;;~j: Rt ~ ".t7'Jlo7~t".}M'.
~ 6- II~ "Jl1' 1"1~ 11, ) ~ II =- er ~ .2.
~'tf..,... I~ ~ .fo a-.is/( ...~ .f",c. ~ ..fi.\ tpl.IA.t A t 1111-Vh -". "T ~'(1.V" I
a d ,- = IJjRI\=. I ~ uA -~ 'K' ". "7 A IA
= tJ.3 XI"/~+1z E~ rl> t~ ~
a) 1027 S
f. Maria throws two stones from the top edge of a building with a speed of 20 m/s. She thrOws one straight down andthe other straight up. The fIrst one hits the street in a time t I. How much later is it before ~nd stone hits,~~~1:
~ 5 s 1f; : ::!- 2lJ ~ L~ .$~T,,;;;;;j;T~ i:il .,. 2IJ ':Ntf14:.. .s/~ j 4-1 1- -/~ 4s D y,-r. ! .~ ~-L... .aT 111 1111~
c. 3 s '-- d vtfC-/ ~l-f'-1 ~il If ~
d. 2~ 11- IA-.:f ..1- t -7f;,/. ~ ~.e. 1 s ,D t'a r- jLl., L- ,/a -J~~ -L 4 I'~
L b..eJ'} ~ /D ~ 6 J pf'T -z; 2. ~ e; --
~ -LJiK 1r~ii:i---~ z.o-- ry ~ .
~ 1/Vol1'Hc.L ~ ~J:S 1t> r;tt, -~-2.0 F<L ..iJIJ.. ~ .
-1.-
1J~O.-
1~ 1'1 ~ 1 f ~ il ~~ Y8 dt. ~ , wd1- "IfO' -:::-
i1- .,.. i2.. 't tl t$ tf~ '-ft 4 k l.~ := 2. "'D4 .
At-:::JI.I1J-t,-: 2t.l..= 2.zrLJ4:/~~ (j;)IS~
.f1I.teLh'~ i2. .j,JbL.
~6.-J
~
'T -lIf-
1-1Jo 2tJ
-f:z.. :. -=- -= 2.0
1 1.S
b) 1024 S
1021 S
S
S
£Xr .P3 Page 5 of 16
Exam I: Physics 121 F03October 3, 2003
James I. GriffinPhysics 2109rrel.301-405-6118
s: A parachutist jumps out of an airplane and accelerates with gravity to a maximum velocity of 58.8 mls in 6.00 seconds. Shethen pulls the parachute cord and aftera 4.0o-second constant deceleration, descends at 10.0 mls for 60.0 seconds, --
reaching the ground. From what height did the parachutist jump, most nearly? .-->'\ I d A I.t ~ -It,Q 914 m ~J d< -t < c6.be C...lf...:::i 6~<.J-;.;;; I.S' 1: -cy. eo "t/t'G2. OM- cr~ 1130m ft, JiJ~~ IA'1t-ltz.
c. 1520m {l) ~.~ <6 < J"Uc JI d~~t4I\ ~ s-e. t1 ~KG" c
d. 1750 m ~W"'..lL ...I -/A.LJ ""A 'C 9 ~ 'I-= -hJe. 1843 m (J) Ib <-t < 7d~c. Ch.1 -a uI ..L t~ :~L1. '0) = 17'. f..
1'L- I~.l.t ,,= Ih,l-f "2. + 'J ) ~ Ilt,F 2.\~i ~~«-..8\/A.c1+-J;.(a2..Z.)l'~),. -// .A -~ t + :f: ~ -r.. v:,.(. v 2.
~ I~ ~11--" ~d t')l. +~. 'iJz.- f a~ tl. .s:e 8 ~ = -<.1s: Z + , L'.~/J(.' Q.l.. = -/d~ .= ...'2.2 ~G2. ...
7 /. h = 1"1~')J1:4 A'd L. 0::; -'"- Lg .c.. , 'Z.
'Vi .i.1 =
ql+ ~» ~ t6ll -I 1"37.1.-117'.1~
2~ .If the displacement of an object is given in SI units by x( t) = -3 t + 4 t- , at t = 2 s its velocity and acceleration are, respectively
; "\
~ci ~~J ,+ ~ ~ 't1~~3~::!> q{:l} ~4
b) r4sJ.,.<.1 'Y6sJt"t 15 ., J
ttl~
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L~ pos~t~ve, poslu~e0: positive, negative
c. negat~ve, neg~~ve )( {t::::oO) -= () :: .Ir ld. negative, posItive ( ,\ --3 -t +e. None of the above, because the signs change with time. X -t= II -+ .t : + 10
~ -, X {-t := t;) = -t... .~d i.f1 M i,,1 ; ~ ,J, t=-2. X l..r p
£xrPage 6 of 16
Exam I: Physics 121 F03October 3, 2003
J ames J. Griffin
Physics 2109rrel.301-405-6118
7. Five boys are pushing on a snowball, and each is pushing with a force of 10.0 N. However, each boy is pushing in adifferent direction. They are pushing north, northeast, east, southeast, and south. (Each boy is pushing at an angle of
o45.0 relative to his neighbor.) What is the magnitude of the total force on the ball?
~~ ~7.1N V£~ ~ IS f'~~ PI t F'1-T F) + F +-&- ~
(C":) 24.1N ~ ~~-+)-~ )~ 27.1 N E~'i-pller- 1.,.,£ ID t.;r~ 1-&1 -~T. r
e. 34.1N g ~ ~pIItleo& ., -l1rU
:=: "
~",
~J/$ ::: ( " i
~ I" +
-"
B. A helicopter is traveling at 40 m/s at a constant altitude of 100 m over a level field. If a wheel falls off thehelicopter, with what speed will it hit the ground? (g = 9.8 m/S2 and air resistance is negligible.)a. 40 m/s ~-b. 50 m/s - ( ) (4 IJ)(C:-) 60 m/s -Vd = "V4X, Vo~ =- ~ } Je" .( ~<
"=[': 1Om/s --44 -t() = ~, J~e.-~~L- "r'::" 1JD~+a.x.t -,
1Jf ~ Vo..+~'4t- : 1J~ t"4t ,=-
0~J c.J&...Jsht~ ,.-:1 q 4
8"' cJ -I1d" A"'J .: -~~-t!~
I .0{ .4 ..= f2M/i'
x
~ -: -, .eo)1\~ 1.
w:- \~\: ~
~A~~= ~
~...~I~ :' 5"1.1l!-~.
~ I,(j ~
@ t ..( t.-d-
M,LJJJe:
4£'""
~.{F
.c\. J~. \fi""' ~ Il>+ J+.I+
(!If>/~~xIPage 7 of 16
Exam I: Physics 121 F03October 3, 2003
J ames J. Griffin
Physics 2109rrel.301-405-6118
edge does the stone travel horizontally? (g = 9.8 mfs2 and air resistance is negligible)
A-t q.:- .S:tfe~
~: ~g: d -L- '-)(/J-f~~ -t 1T; +~ --t t et~~ , J .Xd;:." /' 3 oc. 50m ,~ ~d- r..;C"f7 ~o ~'f 1J..K.o = Vd (;6) d
<:i:) 60 m = 1./(/ ~3~ .-tf ~ ~~e. 70 m .K
--= 1)..ld.e",X.,-.t
v: ~... fvtlx~ tJ,}) =. (,~,t;,jt1~ ~DI.[;,,~d. I = a.70...' .~
~~(J. ..~ ,())(.
fI
~~
,.
.
, if:-.{":{, ~
X'=d-:(~ -:>
o'0. A stone is thrown at an angle of 30 above the horizontal from the top edge of a cliff with an initial speed of 12 mls. A stop
watch measures the stone's trajectory time from top of cliff to bottom to be 5.6 s. What is the height of the cliff?<8 = 9.8 mls2 and air resistance is negligible)
1d -J, , ,( ~ ~ d
'a-#J =- 'li t ud'Ji --t taut2.
A t t ~ # .!: i71l e ~ .J:t!'r b4 k , tAJ~ -"t4)-;:;;--
~l4)~d ~ ~o + 'U~tf +t 14~1Jo : -~~ 4 ..~ t.f2. = -tu-;J ~ 3Doi.f- -t .q '1..
:;" --12. .t. (s.l) +1:f(.£:')~ = -~~., 1S'3.7
A70m(?]1120 mc) 170 md) 220 me) 270 m
~
"tIl12d .tqt6 ;.
I~Jd'="
(fjJ~
wPage 8 of 16
Exam I: Physics 121 F03October 3,2003
James J. GriffinPhysics 2109fTel.301-405-6118
11. A ball is launched from ground level at30 m/s at an angle of 35° above the horizontal. How far doesit go before it is at ground level again. most nearly? ~: ~: ~ = (Vo,,-=~I~ 1)", lId,¥ : 1~/}/w3r) .(a)
GJ ~~: d = ii::xl4) =- ~ + Vd.X fr l.') I wt' -nd .ff .
e. 115 m ~ i -d C.t.~ i<:J ...~ att:.. «(.}1/, It) = <Vo~ + ~ -()
tA1J.w ~ = 'dIlA.)'
.f\ ~ 2.t1.. \ S ~ ft Ylil ~ 'f1/IKt:f J. ,.
f,.lt h~ 10 ~ : 1:!!::~l~~ u- aMA~/ ...~
«t~~:::~~ ~x::o
d:.11.-. tf~
~I
= 30 Cd'\7~S- .2. .30 ~ 3j"0
~); (183.t~.811;zJIO'. $73t) ,
~ S".3"'Jrt. (:l)15W~-~
12.. A 100kg ma5s and a 2.O-kg mass are connected by a light string over a massless, frictionless pulley. ~r -Q *If 9 = 9.8Fs2, what is the acceleration ofthe system when released? r .UN £ "Jr}, tltAt:./~: ~.::,"ft ~ -,.8b;
a. 4 mls 1.df h ~ poSctL..c.. 1&.r"--~~ --, J-tl
Q) 6m1s~ ~ -Ma .= ~,-t "'.2.)t( = + ')It}'1- )')j.2.3 (~Ic. 8 mls NET -d 10 mI 2 e: 12~S2 /1::
( ~.1 ) 4f :: -6- (1.B(J)= t..s-J~z..(-'{. ,.,., I..'.. ~ 2- d' J 2.
-~- D --., C'.ltt:S & ~ o/fJ/'~ f>t{A)* T~ ~ pb ~W""- (. I )l.)I(;.tA .-~
Page 9 of 16
Exam I: Physics 121 F03October 3, 2003
James I. GriffinPhysics 2109rrel.301-405-6118
, , .A horizontal force of 750 N is needed to overcome the force of static friction between a level floorand a 25o-kg crate. What is the acceleration of the crate if the 75o-N force is maintained after thecrate begins to move and the coefficient of kinetic friction is 0.12?
~ 2 a. 1.8 m/s
.2.5 m/s: i ' J ~ 1 -1. t ") {., ~ '(1'. :4)~ 291- Jjc. 3.0 m/s r p~ ."1'"1 -l" .~ \<- 'I'd. 3.8 m/s~ * -F- }I/f.!1lfl
e. 4.2 m/s- -- F - .f = .L4d,... ?0') a = --;r')1 = -M~ FJ/er- --"I
.f"~ F = 7S'b w = @.~ "2. !!1-~2.
7~-Z' -2"+ ----
2S7J
t"1
4-
.-.&,
d.
I f A 70.0kg man jumps 1.00 m down onto a concrete walkway. His downward motion stopsin 0.0200 seconds. If he forgets to bend his knees, what average force is transmitted to his
~b1~n~~~s:estops?-~ 'Cl 1=: ~ ~J~~-b. 7000N IfA"'I~ ~ I' Ay'" "I @L .A(;
c. 5000 N d. 3500N ::rCA.d ~h,~ ~~ ~~'.r ~~ IS
e. 2000N I -.b~V f ~ t§ 2. 1'"1fiiT t""' si ~ ~ VI , ~ -
FA"J~ 7diiiiiii" =-2X 10 -1.J"~c
11$;f1.rN
@'
Ihettl1')r\. -= ~5~a1f.L(
-4- dc:..~JA. ,,~J~ {J. 02.~. -= At;
t! v .£;;;~ -~.f +0 D
(Overf for Page 10 of 16)
/itJ LM nA A/:J
Page 10 of 16
Exam I: Physics 121 F03October 3, 2003
James I. GriffinPhysics 2109rrel.301-405-6118
IS: On takeoff, the combined action of the air around the engines and wings of an airplane exerts an 795~N force on the plane,
directed upward at an angle of 30 degrees above the horizontal. The plane rises with constant velocityinJb~~rt~ dir~Q~while continuing to accelerat~ the horizontal direction. What is the mass of the plane, most nearly?
~AI$T V~~~~ ";:!;> q:1 .=6 = F~er~
f;1d:=. rpf J; Y} ~ +11 a ~ ~
=> !1.=.. -~31'= t2f..!1"3 (d.~" t'f .,~
::- :,-ii4W'.S ~;J; ~
.--16. A 9.Q::-.k;g h~ging weight is connected by a string over a pulley to a 5.o-kg block sliding on a flat table. If the coefficient of
sliding friction is 0.20, find the tension in the string.
~ fifll>Y ~ " 5 kg -:: ')YII l+f :: J./lll~1 ~ }lft /')f1JiJ{)I ~AO.t'ff l:-~ T = ,. g 11/
"rW)J ~ =. 1q I/~T
< .
-F, A
"'"1 'I ..,.~
= '"\1'11,0.r-'J/I)(I 1-rJ I a.. I
-m2..q2..
-IJ '1)-12 LJ
x:
XI:
~d
a. 18N'
b. 23N
c. 28N
A 33N'
~ 38
-y~z. + 'J :=c a.
9 ~/~{; I:
«3) :7' 1+ !!!1
')7)1-
1-.6' + ~
r:;.--£1i=T=
(lrJ
~ m.La.. (8)
~
T- }lA "r)
\A' -
E)I:J:- /fJ
17 a.(3 points) What does the spring scale register before the elevator starts to move?
17b.(3 points) What does it register during the first ~ E~y, ~ .1 ~ ~~ :. .~'; -io c..ws".J
~.~ ~..A.llf:.18(a)(3 points) What does it register while the elevator is traveling at constant speed?
18(b)(3point&) What does it register during the negative acceleration?
~~ d -61~ d". ~~ ~ ~ c...,.ft:
q,-.,r ~ 'f " " {1«4A-~J~1:-1.9~Yf.e£'l)
-
Fr IS
'.'1 "
~ a. =- A%f ;:
-
FAle-r- ==
~
1L... Fs +11f=
~
8F:osI=.
-..~ J -=!? a, =-()
~
R= -'Fi:
C..1S".,t~ =>
~
-~3
'8~~
~ ~~ 4.~d,~
a.' = -I.t )wL -A 'F/1 ~/iT .r.;~Z=- v. I (, "'" /[2.
-t e',J
IB(~) ,- ~ -'..;\a ro-
~
..,fi=
1"
-.S-.i.3A1~~' =
~.1d./l"
i EX ..c !;;:0 Ltl7lt' AIS ,p /t:J ~ ~ (9}
J<:f...sf- )/ .= ~
...,Fu~r '::'
~
1fL=-
1'Itd-1lt.e
fIll =of FA
~,
)(
..2.()
-"' -f"iII.1T' FN d = )) a..
-.~ .
FpeT = FA..'. ')'J + l1i + ~-tr.,J= }l~ ,.; f o-d dt~A IJ .."/~.et/t' le if
J ,,~ YI «d I~ +0 ~~ /-&1--Y- ~ p..f1 l1 Q:J .:=. f~ i" M 'J ~ ..,. 'r1 !J
:= {) l.f I~ , < lM1{
-d:/ --~~ -~= -l.MJ11
= 11/11- F/ .:= 11-7-ltt.:4Itl
;:,c-.,l,.d~';/l"rA.~FA ~ J~ v ..1 4{1'
...,.
J\1~ ,,""A3 l:-""Xof..
1-r Fj= "1 ; U~
I ~J ::: It1';
fwar tI.~1 ~ ~A ~ -F ~ : -t ( f I::; I..'.' 4b'"# =
~ :: ..(F~I £.., +s-- p.
"Y1~=
~
1l,..
.x- u-'- f-" 'ZJ 1.,.,/! ay:~A -~ := Itftl -{11-37)4/11 ~ q/ll
q '/15"' =-
IJu-J/ '1!-t .1 :if '=' I:. J (!Ll:) 2...11 ax =
ax =
--: -!: a.. t 2;. 4: { c ){ 3' ~ :" 2. 7 P'f..
9
(:.' rl-.i FIO4«' => ~ "-~-
( LJ~ of d/J'4(e.J ::)?o~)