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16
.
Exam I: Physics 121 F03
October 3, 2003
James J. Griffin
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 the
full exam. For each problem fill in the circle next to the letter of your chosen answer on
the NCS answer sheet using a #2 pencil, making sure that the number of the line
correspondsto the number of the problem you are answering. There is only one correct
answer for each problem, and no subtractions will be made for wrong answers.
Use only lines 1 through 16 on the NCS sheet.
1. Which of the equations below is dimensionally incorrect?
Insert the letter of your chosen answer into your liC$'
answer sh~.
a. v2 = VO2 +2ax
-1 (Llr)
.I :" l'lr}2
of 2 (i;r~L
fdi
b.
Ic.
d.
~
a = ao + v!t
v=xlt
£L
A
x/y = Cos ~
X(t) = Xo + Vo t
'J
2
L.lra
(')
:.
l.fr
~
JJ
'li.
e)
L ~
.lfr;
(
"7
+
lLooI
'Ir
/2',
7'1
@
~
~)
d.4--S/~/t;g
2.
IJ/ ~
(
@
L. ..,.
!-1" ~
c,..-d
LL.T
~
~).I;
m
d,)11~/AI
L'.
~
(Over for Page 4 of 16)
In
e.#k4S IS;e..t"
cJ
dl d
&I
1'2.
Page 4 of 16
Exam I: Physics 121 F03
October 3,2003
JamesJ. Griffin
Physics 2109fTel.301-405-6118
3. Supposethat 2 macrol!:letoeritesper century strike each squaremeter of the surface of some distant moon,
and that each a sphereofrndius 0.3 mrn. Given that a year isabout 3x107 s, how many secondswould it take
A
~
~-~to cover the moon's surf~cewith meteorites UDto-a dep!llJJfAfi-C1ll?
3 -A
L (.JL.rr~/-')1f
(J'YI ~"Wl.l.4
£
a) 1027 S
b)
1024
1021
)rI6A ..,~
J.
0-
-71
IM-.
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---'
1t~ ~
Ff1'P"'
~6S (l
N-
V/"..
-;;~j:
1zr,,",
AII..-~/
I-~
V.
~.1
'l..I'8~-
(0./"..7;JJ
.At
:::(J.2It
L~
~
R=~'1Y)tl2
,/}1jZ
Rt
1.
A L 'ttt -D--IJ
~ --u~r---10 3
"ID-;~3=
Z..z X t()
,...
/0 .tJ .:f.(~
:: 2Xlo..~~
"Z
F~
3x(~-P'<
'J
".t7'Jlo7~t".}M'.
~
S
~
S
6-
S
~'tf..,...
S
a
II~
I~ ~
d
.fo a-.is/(
Vh
-".
,- = IJjRI\=.
I ~ uA -~
=
f.
~
6
tJ.3
XI"/~+1z
"Jl1' 1"1~
11, )
...~
"T
~
II =- er ~
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~'(1.V"
'K'". "7 A IA
E~
rl>
.2.
..fi.\
I
t~
tpl.IA.t A t 1111-
~
Maria throws two stones from the top edge of a building with a speed of 20 m/s. She thrOws one straight down and
the other straight up. The fIrst one hits the street in a time t I. How much later is it before ~nd
stone hits,~~~1:
~
5s
1f; :
::!- 2lJ ~ L~ .$~T,,;;;;;j;T~
i:il
.,. 2IJ ':Ntf14:.. .s/~
j
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4s
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y,-r.
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111
c. 3 s
'-d vtfC-/
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d. 2~
11IA-.:f
..1-7f;,/.
~
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e. 1 s
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t'a
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rjLl., Lb..eJ'}
~ /D ~
~
-LJiK
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pf'T -z;2. ~
4
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--
ry ~ .
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1t> r;tt,
-~
1f
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-2.0 F<L ..iJIJ.. ~
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, wd1"IfO'-:::i1- .,..i2.. 't tl
t$ tf~
'-ft
4
k
l.~ := 2. "'D4 .
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1111~
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(j;)IS~
-1Jo
.f1I.teLh'~
i2.
.j,JbL.
-f:z..
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Page 5 of 16
.P3
Exam I: Physics 121 F03
October 3, 2003
JamesI. Griffin
Physics 2109rrel.301-405-6118
s: A parachutistjumps out of an airplane and accelerateswith gravity to a maximum velocity of 58.8 mls in 6.00 seconds.She
then pulls the parachutecord and aftera 4.0o-second constantdeceleration,descendsat 10.0 mls for 60.0 seconds, -reaching the ground. From what height did the parachutistjump, 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. OMcr
~
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-= -hJ
e. 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
) ~
,.
-//
.A
~d
t')l. +~.
I~ ~11--"
l.
~/J(.'
.s:e 8
.=
Q.l..= -/d~
Ilt,F
-~
'iJz.-
f
2.\~
t + :f: ~
~
...'2.2 ~G2.
i ~~«-..8\/A.c1+-J;.(a2..Z.)l'~)
-r.. v:,.(. v
2.
a~
= -<.1s: Z + , L'.t
...
4
A'd
L.
0::;
-'"-
Lg
7
/.
.c..
,
h
'Z.
=
1"1~')J1:
'Vi .i.1 =
»
~
.If
;
"\
the
L~
0:
c.
d.
displacement
~
of
an
t6ll
-I
object
is
ql+
1"37.1.-117'.1~
given
in
pos~t~ve,poslu~e
positive, negative
negat~ve, neg~~ve
negative, posItive
SI
units
by
x( t)
= -3
~
2
t + 4 t- , at t = 2 s its
velocity
)( {t::::oO) -= ()
and
acceleration
are,
respectively
:: .Ir l
(
,\ --3
-t +
e. Noneof theabove,
because
thesignschange
withtime. X -t= II -+
.t : + 10
~
-, ~X {-t :=t;)
,J, = t=-2.
-t...
X l..r
.~d p
i.f1 M i,,1;
~
ttl
~ci ~
~J ,+ ~
~
't1~~3~::!>
b) r4sJ.,.<.1
'Y6sJt"t 15 .,
J
(Over for Page 6 of 16)
q{:l} ~4
£xr
Page 6 of 16
Exam I: Physics 121 F03
October 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 a
different direction. They are pushing north, northeast, east, southeast, and south. (Each boy is pushing at an angle of
o
45.0 relative to his neighbor.) What is the magnitude of the total force on the ball?
~~ ~7.1N
V£~
~
IS
f'~~
(C":) 24.1N
~
27.1 N
e.
PI
t F'1-T
E~'i-pller-
34.1N
g
~
"
,
+
1.,.,£
~pIItleo&
.,
F
+-&-
ID t.;r~
~
~
~~-+)-~
1-&1 -~T.
r
-l1rU
:=:
~
F)
"
~J/$ ::: ( " i
M,LJ
JJe:
~
I" +
.c\. J~.
\fi""'
~
Il>+
J+.I+
4£'""
"
-
~.{F
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 the
helicopter, 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
(C:-) 60 m/s
-Vd = ( "V4X, Vo~ ) =~ } IJ)
Je" .( ~<
(4
"=[': 1Om/s
e.-~~L-
"r'::"
1JD~+a.x.t
1Jf ~
--44
-,
Vo..+~'4t-
-t()
:
=
~,
1J~ t"4t
J~
,=-
0
~J
x
c.J&...Jsht~
8"' cJ -I1d"
,.-:1
q
4
A"'J .: -~~-t!~
~ -: -, .eo)1\~ 1.
I .0{ .4
..= f2M/i'
w:~
\~\: ~
~A~~
...~I
= ~~
@
:' 5"1.1l!-~.
~ I,(j ~
t ..( t.-d-
)
(!If>
/~
~xI
Page 7 of 16
Exam I: Physics 121 F03
October 3, 2003
J ames J. Griffin
Physics
edge does the stone travel horizontally?
(g = 9.8 mfs2 and air resistance is negligible)
A-t
~:
~g:
d -L-
c.
50m
,~
<:i:)
e.
q.:-
.S:tfe~
'-)(/J-f~~
~d-
r..;C"f7
-t 1T; +~--t t et~~
~o
=
~~(J.
tJ,})
~~
.-tf
~
=. (,~,t;,jt1~
-:>
(;6)
3
d
o
~~
~DI.[;,,~d.
I
= a.70...'
.~
,())(.
,.
.
,
-:(~
.K
/'
Vd
1)..ld.e",X.,-.t
..~
fI
.Xd;:."
1J..K.o =
1./(/ ~3~
--=
~... fvtlx~
, J
~'f
60 m
70 m
v:
2109rrel.301-405-6118
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 speedof 12 mls. A stop
watch measuresthe 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 resistanceis negligible)
1d
A70m
(?]1120 m
c) 170 m
d) 220 m
e) 270 m
'a-#J =- 'li
At
t ~#
~l4)~d
t
ud'Ji
.!:i71le ~
-J,, ,( ~
~ d
--t taut2.
.J:t!'r b4 k
, tAJ~
-"t4)-;:;;--
1Jo
: -~~
t.f2. = -tu-;J ~ 3Doi.f- -t .q '1..
~ ~o
+ 'U~tf 4 +t ..~14~
~
:;" --12. .t. (s.l) +1:f(.£:')~
I~Jd
'="
~
tqt6 ;.
12d
.
(fjJ
"tIl
= -~~.,
1S'3.7
w
Page 8 of 16
Exam I: Physics 121 F03
October 3,2003
JamesJ. Griffin
Physics 2109fTel.301-405-6118
11. A ball is launchedfrom ground level at30 m/s at an angle of 35° above the horizontal. How far does
it go~:
~:
before it is at ground
~ level
= (Vo,,-=~I~
again. most nearly? 1)", lId,¥ : 1~/}/w3r)
.(a)
GJ
~~:
e.
ii::xl4)
115 m
uaMA~/
l~
d =
=-
+ Vd.Xfr
~
i<:J ...~ att:.. «(.}1/,
~
~
~
l.') I wt'
It)
=
-nd
<Vo~ + ~
i
.
-d
-()
C.t.
tA1J.w ~ = 'dIlA.)'
...~
.f\
~
2.t1..
\S ~
ft
f,.lt
«t~~:::~~
x::o
.ff
Ylil
h~
10 ~
30
Cd'\7~S-
~ 'f1/IKt:f
:
J. ,.
1:!!::~
~
11.-.
d:.
tf~
=
;
.2. .30
~)
(183.t~.811;zJIO'.
~
3j"0
$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.
If
9
=
9.8Fs2,
a. 4 mls
Q)
6m1s~
c. 8 mls
d 10
e:
12~S2
mI 2
what
is
the
acceleration
1.df
~
ofthe
system
when
released?
h ~ poSctL..c.. 1&.r"--~~
-Ma
.=
~,-t
NET /1::
(-'{.
*
~
I
r
T~
~
-~pb ~W""-
(
.UN
£
"Jr},
~.::,"ft
--,
"'.2.)t(
=
+
)
4f
,.,., I..'.. ~ 2- d'
~.1
D
--.,
(. I )l.)I(;.tA
C'.ltt:S
.-~
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::
&
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-6(1.B(J)=
J 2.
~
~
tltAt:./~:
o/fJ/'~
J-tl
(~I
t..s-J~z..
f>t{A)
r -Q
~ -,.8b;
*
Page 9 of 16
Exam I: Physics 121 F03
October 3, 2003
JamesI. Griffin
Physics 2109rrel.301-405-6118
, , .A horizontal force of 750 N is neededto overcome the force of static friction between a level floor
and a 25o-kg crate. What is the accelerationof the crate if the 75o-N force is maintained after the
crate begins to move and the coefficient of kinetic friction is 0.12?
~ a. 1.8 m/s2
J
r
*
e. 4.2 m/s-
p~
~
1
-1.
-l"
.~
F
-
.f
= .L4d,...?0') a =
."1'"1
t " ) {., ~ '(1'. :4)~
\<- 'I'
291-
Jj
-F-
}I/f.!1lfl
--
')1= -M~
.f"~
'
i
.2.5 m/s:
c. 3.0 m/s
d. 3.8 m/s~
FJ/er- --"I
F = 7S'bw
=
7~-Z'
--
-2"+
--;r
.~
-
"2. !!1~2.
@
2S7J
t
"1
I f A 70.0kg man jumps 1.00 m down onto a concrete walkway. His downward motion stops
in 0.0200 seconds. If he forgets to bend his knees, what average force is transmitted to his
~b1~n~~~s:estops?-~
b.
7000N
c. 5000
d.
3500NN
e.
2000N
IfA"'I~
::rCA.d ~h,~
V f
~
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'Cl
I'
Ay'"
1=:
~~
t§ 2. 1'"1fiiT
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~~'.r
t""' si ~
4-
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I
VI , ~
-.b~
-
.-.&,
d.
1')r\. -= ~5~a1f.L(
-4dc:..~JA.
,,~J
~
{J. 02.~.
-= At;
t! v .£;;;~
-~.f +0 D
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Page 10 of 16
Exam I: Physics 121 F03
October 3, 2003
JamesI. Griffin
Physics 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.=..
::-
.-16. A 9.Q::-.k;g
h~ging
-~31'=
"
t2f..!1"3(d.~
t'f .,~
:,-ii4W'.S
~;J; ~
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
~
"
{)I ~AO.t'ff
l:-~
<
.
-F
,
"'"1
"rW)J
~ =. 1q I/
A
..,.
'I
IJ '1)-12
18N'
b.
23N
c.
28N
A
33N'
~
38
T
~ }lft /')f1JiJ
= ,. g 11/
~T
~
a.
l+f :: J./lll~1
5 kg -:: ')YII
LJ
r-'J/
I)(I
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T-
}lA
x:
-
"r)
\A'
-
XI:
~d
«3) :
-y~z.
+ 'J
9 ~/~{;
T=
1-.6' + ~
r:;.--£1i=
:=ca.
I:
7'
1+ !!!1
')7)1-
1-rJ I a.. I
=
~
-m2..q2..
'"\1'11,0.
m.La..
(lrJ
(8)
/fJ
E)I:J:-
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 ~ ~~ :. .~';
~.~
18(a)(3 points) What does it register while the elevator is traveling at constant speed?
~..A.llf:.
18(b)(3point&) What does it register during the negative acceleration?
Fr
~~
IS
d
q,-.,r
'.'1
-61~
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d".
'f
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~
"
~ c...,.ft:
{1«4A-~J~1:-1.9~Yf.e£'l)
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a.
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=-
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==
Fs
+11f=
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'8~
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J
-=!?
-..
a,
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=>
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:= {) l.f I~
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fwar AtI.~1 ~ ~
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.
x-
u-'- f-"
~A
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ay:
:= Itftl -{11-37)4/11
~
q/ll
IJu11 ax
=
t .1
q '/15"'
ax
9
=
=-
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: