KLI /A*rswEtS
PHYSICS221
FALL 2OO5
EXAM II
Name (printed):
lD Number:
SectionNumber:
RecitationInstruction:
INSTRUCTIONS:
Put away all materialsexceptfor pens,pencils, erasersand your calculator.
ll.
This l2O-minuteexamcontains30 equallyweightedmultiple choiceproblems
worth a total of 85 points (75 points + 10 extra credit points).
lll.
In marking the multiple choicebubblesheetusea number2 pencil. Do NOT use Ink. If
you did not bring a pencil, ask for one. Fill in the appropriatecirclescompletely. If you
needto changeany entry, you must completely eraseyour previous entry. Also. circle
your answerson this exam.
lv.
Carefully ready eachproblem and its five possibleanswersbefore beginning to work the
problem. Selectone and only one answerfor eachproblem. Choosethe answerthat is
closestto the correct one.
v.
Pleaseturn over or cover your bubble sheetwhen you are not marking it.
vi.
Before handing in your exam, be surethat your answerson your bubble sheetare what
you intend them to be. If you want to, copy down your answerson a piece of unused
scratchpaper for comparisonwith the answerkey to be postedlater.
vii.
When you are finished with the exam,place all exam materials,including the bubble
sheet,the exam itself, and scratchpaperthat you usedfor the exam, in your folder and
return the folder to vour recitation instructor.
viii.
No cell phonecalls allowed. Either turn off your cell phoneor leaveit at home.
Anyone taking cell phone calls must leavethe testingroom and will not be allowed to
return.
GOODLUCK
A 100-9 ball traveling at 20 m/s horizontally to the left is hit by a racket. The ball and the
racket are in contactfor 0.2 ms. As a result of the blow, the ball leavesthe racket traveling
to the right at anangle of 45 degreeswith the horizontal, at20 m/s. What is the magnitude
of the averageforce exertedby the racketon the ball?
3I .
A . 0
7 . 7 x 1 0 3N
B.
,/-a.,
acj
D
E.
1.8x lo4N
2.0xl0a N
2.5 x l}a N
32. A 20-kg child standson a 10-kgwagon that rolls at2.0 m/s to the right. The child jumps to
the left, at 1.0 m/s relative to the ground. Comparethe changein momentum of the child
and the changein momentum of the wagon.
A.
B.
l r
\9
D.
E.
33.
AF"n'o= -4LF*^ron
= -2LF*uron
Ap"n,,o
: -Ll*uron
AF"n,,o
: &*ugon
AF.n,,o
= 2LF*unon
AF"n,,o
The object shownbelow is madeof two identical,uniform rectanglesof sideso and2a.
Find the x componentof the centerof massof the object.
A.
B.
C.
0.25a
0 . 3 5a
0 . 5 0a
m)
Y
0.75a
l . 5 oa
3 4 . The three objectsshown below are eachmadeof two identical,uniform rods. They can
rotate about the axes indicatedwith a dotted line. Which of the following statementsabout
their momentsof inertia is true?
A
A.
B.
,^\
(ry
E.
16> Is> Ig
16: Is> Ig
Is> Ig> IB
1e-:Ig>IB
Is> I^> Ic
B
C
35.
A uniform solid sphereof massM - 2.0kg and radiusR - 30 cm rolls without slipping on
a horizontal surfaceand then up an incline as shown in the figure below. While the sphere
is on the horizontal section,the translational kinetic energy of the center of massis 30 J.
Determinethe maximumheighth thespherewill go on the incline.
A.
B.
C.
D-
0.8m
1 . 5m
1 . 7m
1 . 9m
2.rm
LU
36.
When the spherefrom the previousproblem is rolling up the incline, the angular
and of the net torque aboutthe centerof masspoints
accelerationpoints
into the page,into the page
into the pa5e,out of the page
out of the page,into the page
out of the page,out of tlre pug.
Both quantitiesare zero.
A.
B.
_C.
G)
E.
37.
A uniform rod of lengthL andmassmis attachedto the ceiling by a hinge. A small clay
ball of equal massm traveling horizontally with speedv hits it right at its center(seefigure
below) and sticks to it. What is the angularspeedof the rod right after the collision?
A.
0.44L
L
B.
0.s01
L
0861
rc)
\__-/
L
D
E.
.
v
L
1.51
L
hinge
38.
Severalforces F areapplied to the 2D objectsbelow. All forceshave equal magnitude.
All the objectshave the samemass,uniformly distributed. Which of the following
statementsabout the magnitudeof the net torque about the centerof massof eachsystemis
true?
IAI
T
#
rnl
,{
Tg
d
rs-- rrl rg
rs ( rc 1r;
G,
C.
39.
tel
IBI
-
D.
Tc1ts1T6
E.
rg1t61xs
The displacementas a function of time for an object in simple harmonic motion is plotted
for 10 s:
x
4.0 cm 2.0 cm -
Estimatethe period of the motion
A
G)
C.
D.
E.
l s
3s
5s
7s
1 0s
40. Using the plot in the last problem,ifx(r):l
r\
C,
B.
C.
D.
E.
cos (at + p), determinetp.
-nl3 rad
-nl6 rad
0 rad
nl6 rad
nl3 rad
4 1 . T w o p o i n t c h a r g eQs r : 1 . 0 p C a n d q 2 : 2 . 0 p C a r e f i x e d o n t h e x a x i sa t x l : - 2 . 0 c m a n d
x2.: 1.0 cm. Determinethe electricforce exertedon q1b! q2.
A
q,
D.
E.
42.
-(4s N) i
-(20 N) i
0
(20N) i
(4s N) i
Considera positive point chargeq locatedat the centerof a cubical box (figure below
showsside view). When anotheridentical chargeq is placedat point P, the net electric
flux through the box
and the magnitudeof the electric field at point A
A.
B.
C.
increases,decreases
increases,staysthe same
staysthe same,staysthe same
staysthe same,decreases
staysthe same,increases
iA
o p
I
I
I
I
I
I
I
- 1.31x
speedfor a 100-kgobjecton thesurfaceof Pluto(Mnuto
43. Determine
theescape
1022
kg,ftpru,o:
1.15x 10u*).
A.
0.872km/s
(ry
r.23kmJs
/->-\
C.
D.
E.
3.45km/s
5.68km/s
ll .2 km/s
44. A 50-kg beam hinged to the wall is kept in equilibrium through a cable attachedto the free
end, seefigure below. Determinethe tensionon the cable.
A.
-E
l9
D.
E.
98.0N
ll3N
1 4 1N
245N
280N
45. The figure below showsthe electricfield lines in a regionof space. Comparethe
magnitudeof the electricfield at points A, B and C.
A.
B.
C.
D.
G)
E6<Es<Ec
Ec
Ea.: E11^:
Ea.: Es> Ec
Ea> Ea: Ec
Ea,>EesEc
46. A uniform plank is supportedby two equal 120-N forces at X and Y, as shown. The
support at X is then moved to Z (half-way to the plank center). The supporting force at Y
then becomes:
A.
A
240N
l60N
D.
E.
6ON
4ON
re, 8oN
47 .
The diagram showsthe electric field lines in a region of spacecontainingtwo small
chargedspheres(Y and Z). Then:
t
\
\
€(v)
l
/
\
l
-x.t-\./
>
*
/XYXIK
I \\>/
A.
B.
Q..
!p/
E.
I \
Y is negativeandZ is positive
the magnitudeof the electric field is the sameeverywhere
the electricfield is strongestmidway betweenY andZ
a small negatively chargedbody placedat X would be pushedto the right
Y and Z must have the samesign
48.
A very long^,insulating cylinder with a radius of 10.0 cm has a uniform chargedensity of
+3.00 x l0-8 Clm3. What is the magnitudeof the electricfield 4.00 cm from the centerof
the cvlinder?
N
C
B.
N
| .69x 103
C
C.
1 . 3 5x l 0 a
N
C
D.
N
1 . 6 8x 1 0 s
C
E.
N
7.32x 106
C
49.
Which of the following objectswill havethe largestvalue of I, rotationalmoment of
inertia, about the indicated axis of rotation(*) that extendsdirectly out of the page?
c)
t\
L
T\\ttu R-rttG6F
tf,$\SS f\
I
ffti\ss
aF)
a
b
c
bandc
a andc
\lsr ov
(\&\ss ffr
T
Ll I
Ro b o F
J\
A .
B .
C .
..--D - |
?I
f\\
JJ
P<>{f.}T f{\&55
(v\
[.ooi-ff
lh+"ooap
/'n=o'
I
J,_
5 0 . A 1.00 kg massslidesfrictionlesslydown an inclined plane,lowering its centerof massby
2.00 m. At the bottom of the plane it collidesinelasticallywith a 5.00 kg massand the
combinedmassslidesover a rough floor, pp:0.250. How far doesthe combinedmass
slide?
A.
B.
A
Al
E.
2.00m
1 . 1 5m
m
0.33
0.22m
0.11m
-i
(.lJ=O,Tocq '
lcntU
51.
A personof mass60.0 kg initially runningtangentiallyat a fixed speedjumps onto the
edgeof a spinninguniform disk. The disk has a massof 100 kg and a radiusof 5.00 m. If
the disk initially has co: 0.700 radls coming out of the page(i.e. rotatingcounterclockwise) how fast doesthe personhave to be running such that both the disk and person
areat rest after the person lands? Treat the personas a point mass.
0.70m/s
I .41m/s
2.04mls
292 mls
4.08m/s
52. If we assumethat the period of the moon's rotation aboutthe earthis 28 days, what is the
distancebetweenthe earthand the moon?
A.
B.
A
LD
E.
53.
l . l x 1 0 7m
l . l x 1 0 8m
2.3x108m
3.9x 108m
l . l x 1 0 em
Which of the following hasthe largestvalue for the angularfrequencyof its periodic
motion?
A.
B.
A simplependulummadefrom a 10 kg massand a 4 m long rope with no damping.
A simple pendulum made from a 10 kg massand a 4 m long rope with damping
b- 5N't
C.
D.
( E.,
\*-/
a ,prirTg,hung vertically, with a spring constantk : 40 N/m and a 10 kg masshung
from it.
N't
A l0 kg masshung verticallyon ak:40 N/m spring,with dampingb - 5
A physicalpendulummadefrom a uniform 1 m long, m : 1 kg rod hung vertically
from one end that experiencesa driving force F(t):A cos[(+:!!)tl
54. A l3 kg block is at rest on a horizontal,frictionlesssurface.If the block is suddenlyhit by
a bat and, as a result, startsto move to the right with a velocity of 8 m/s, what was the
magnitudeof the impulse associatedwith the blow?
B.
c.
D.
E.
55.
1 0 4N . s
4 1 6N . s
1 0 4J
416I
Needto know how longthe batandblockwerein contactto provideanswer.
Two massesin outer spacebounceoff of eachother in a collision. Which of the following
statementsis correct?
A.
B.
A
(ry
E.
The collision hasto be elastic.
The collision hasto be inelastic.
The total mechanicalenergyof the system(the two masses)hasto be conserved.
The total momentum of the system(the two masses)has to be conserved.
Both (C) and (D)
56.
A car is moving forward with a constantspeedof 30 km/hr. If the wheels are rolling
(without slipping) and have diametersof 66 cm, what is their period of rotation about the
axles?
A.
CE)
C.
D.
E.
57.
6.9l x 10-2s
2.49x lo-rs
2.20s
2 . 5 2 x1 0 rs
9.09x10rs
A uniforil, I meter long, l0 kg rod rotateshorizontally about its centerpoint, (the 50 cm
mark). Initially it hastwo point masses(eachwith m : 5009) locatedat its center. At t 5s thesemassesare allowedto slideto the endsof the rod (the 0 cm and the 100 cm
tuo
points). If att:0 s the rod hasco:5
, whatis crlfort - 10 s?
s
A.
rad
6.50
S
B.
rad
5.00
S
C.
rad
4.38
S
@
E.
rad
3.85
S
t.47
rad
s
58.
The diagramshowsthe electricfield lines dueto two chargedparallel metalplates. We
concludethat:
metal
,rplates
A
qry
C.
D.
E.
the upperplate is positive and the lower plateis negative.
a positive chargeat X would experiencethe sameforce if it were placed at Y.
a positive chargeat X experiencesa greaterforce than if it were placedatZ.
a positive chargeat X experienceslessforce than if it were placedat Z.
a negativechargeat X could have its weight balancedby the electrical force.
Two unchargedmetal spheres,L and M, are in contact. A negatively chargedrod is
brought close to L, but not touching it, as shown. The two spheresare slightly separated
and the rod is then withdrawn. As a result:
59.
A.
B.
C.
P=_
(tr,
both spheresare neutral
both spheresare positive
both spheresare negative
L is negativeand M is positive
L is positive and M is negative
insulating supports
Two protons (p1and p2) and an electron(e) lie on a straightline, as shown. The directions
of the force of pt on e, the force of pt on e, and the total force on e, respectively,are:
60.
€)
A.
l,€,J
B.
<-, -+' +
_C.
;G.
(DJ
E.
J,€,€
€,J,€
e,e,e