PHYSICS 22I
EXAM 2
FALL 2OO4
QUESTIONSWORTH 3 POINTS.
29.
A 1.50kg block is pushedagainsta springwithnegligiblemassandforceconstant
k: 300N/m, compressing
it0.220m. Whentheblockis released,
it movesalonga
frictionless,horizontalsurfaceandthenup a frictionlessinclinewith slope26.0". How
far doesthe blocktravelup, along,the incline(/) beforestartingto slidebackdown?
A)
B)
C)
D)
E)
0.220m
0 . 5 5 1m
0.821m
1 . 0 8m
1 . 1 3m
k:300 N/m
m - 1 . 5 0k g
n'-J
l* o.z2o
30.
At time t:0 a grinding wheel has an angularvelocity of 20.0 rad/s. It has a constant
angularaccelerationof 10.0 rad/s2until att - 3.00 s a circuit breakertrips. From that
point on (i.e. for t > 3.00 s) it undergoesconstantacceleration,turning through 400 rad
before it stops. What was the accelerationthat stoppedthe wheel?
A) -lo.o#
g
B) -8.17
-6.67
g
c)
D)-s.oo
#
3
E ) - 3 . 1#
3 1)
Two massesare on a ftictionless 1-D air track. Sketchesof before and after the collision
are shown below. Which of the following is true?
r/--o
Before:
M
3kz
6a.nl S -..
After:
l r l
I
\ skr I
A.
B.
C.
D.
E.
The collision is elastic.
The collision is completelyinelastic.
The collision is inelasticwith AK.E. : -24 J.
The collision is inelasticand AK.E. : -54 J.
The collision is inelasticand AK.E. cannotbe determinedwithout a value of vs.
32)
A 4.00kg and3.00kg massareattachedby a
pulley. If
massless
ropethatrunsovera massless
the massesstartat restandthe horizontalsurfaceis
frictionless,whatis thevelocityof the 3.00kg mass
just beforeit hitsthefloor, 1.50m below?
t,uoL"B
f Rtctl<lpt-€ S S
suRFNc€.
1
\ = l.SO'nn
A. 3.55mis
B . 5.42mls
C . 9.81m/s
D . 19.3m/s
E. Masseswill not move.
Tttf- C.6cO
y=,-5So
C...n".
X=o
X=?-'(Pc/vn
f F$ro Tlt€AJ F€L€NsEO
I
A springwith k:8.00 N/m is compressed
by 5.00cm by a 5.00g masslIf thecoefficient
of ftiction is p1 : 0.600,whatis themass'svelocitywhenthe springit is attachedto is
expandedby 2 cm?
A. 1.59m/s
B. 1.73mls
C. 1.83m/s
D. 1.96m/s
E. 2.00m/s
34)
0
A spring with a2kgmass on its end hangsfrom the ceiling. The massis 100 cm from
the ceiling. When an extra I kg is addedthe spring extendsanother 20 cm:1What
wnarls
is rne
the
valueof this spring'sspringconstant?
A.
B.
C.
D.
E.
8.2N/m
25 N/m
37N/m
49 Nim
150N/m
l
\
LTo
].r€.\,t
.- tTS
li.)
l-
"F; tr-rRQ,trJv'ft
F-^ql
"',rr i rO
1r rt
A carNidesdbwna frictionlessracetrackasshown.
point f 3
r-.1 Points) *d t *" on a straightsegment,
'
wi.thpoini ( Z
areon a circularloop-the-loop,
-iT,
Lt
point
vertically
and
rise
the
car
having
Zf travingi-nF-carmovehorizontally,andpointl is-offfta}
f
point
points
or
does
horizontalsegment.At which
leastrinstantaneous
work
do
the
the forceof gravity
v
I
35)
dw?
tir
\
? 3
A. 1
B. J
C. 5
D . I andZ
E. 4 a n d 5
36)
I
A uniform disk of massM and radius R has a
masslessrope wound aroundit. The rope is also
attachedto a smaller massm which startsa
height h abovethe floor. Which expressiongives
the speeal"l of m just before it hits the floor?
A. \ffi
B.@
c @
D.@
E. None of the above.
37)
MomentumhasS.I.unitsof
A.N.m
B *
c s
D .N . s
E. BandD
,,
/
i
DJ )
pAGNtrus€)
38)
At The Olympics there is a paddedareabeneaththe bar over which pole vaulters
.\
leap. This paddinghelps protect the vaulter from injury by:
,.
f
\
A. Increasingthe time it takesthem to stop.
""' ---"/I
B. Decreasingthe impulse that they experienceupon stopping.
C. Increasingthe averageforce that acts upon them so they are brought to rest in a
shorterdistance.
D. All of the above.
E. None of these.
3e)
Over the courseof a round trip, how much work is done by a conservativeforce?
A zero
B.
C.
D.
E.
40)
As a large box slidesacrossa horizontal floor, which force doesthe most work?
A.
B.
C.
D.
E.
4l)
rf\)
(Magnitude of force) [(distancetraveled)/zr)].
\-__/
(Magnitude of force) (l/2 distancetraveled).
(Magnitude of force) (distancetraveled).
This can be any value betweenresponsesA and D, dependingupon the orientation of
the force relative to the path.
a,
(
The normal force.
The force of ftiction.
Neither of thesedoesany work
Both of thesedo the sameamount of work.
Either responsea or b, dependingupon the value of p,r.
$-
\
\IJ
Compare the moment of inertia of a pear about three different axes of rotation:
3
A
Stringof
negligible mass
iI Un i
l
A. IA:Ig:IC
B. Ia>Ie>Ic
C. Is>Ie:Ic.
D. Ig>Ie>Is.
E. Is>Ic>Ie
\
/
,
42)
A sledrestson a plain coveredwith snow.A kid with mass40 kg comesrunningand
jumps horizontallyontothe sledwith a speedof 1.2m/s.The sledwith the kid begins
movingwith 1.0m/s.Findthemassof thesled.
A.
B.
C.
D.
E.
43)
2.0kg
4.0kg
8.0kg
10kg
12kg
All the forces in the figure below havethe samemagnitude.In which caseis the net
torque on the object greater?
44)
A force F out of the pageis applied at point P of an H-shapedobject made of three rods
eachof massm and length L. One of the rods is fixed so the systemcan rotate about axis
A. Find the magnitudeof the angularacceleration.
A. u^ - _ 34 mF L
B.
F
u^ -_ 1T 2 - m t
C.
u-,
D.
^ _ t 2 F
uB ,nL
? t r
,r,L
G
S
45)
A force F* : (2.00 N/m)x + (4.00 N/m2)x2 actsupon a 2.00-kg block during a
displacementfrom x - 0.00 m to x : 3.00 m, Find the work done by the force.
A.
B.
C.
D.
E.
46)
34J
45J
82J
1 0 4J
126J
G;
A 200-kg box sits on the floor of an elevator.The elevatoris initially at rest and begins
moving up. After 0.600 m, its speedis 2.00 m/s. Find the work done by the normal force
exertedby the floor on the box.
A. OJ
B. 400J
c. 850J
D. ll80J
E . 1 5 8 0J
47)
A persondragsa heavy box up along a l5-m long r€Impin 45 s. The ramp makesan angle
of 45o with the horizontal. The personpulls with a constantforce of 300 N that makesan
angle of 30o with the ramp. Find the averagepower usedby the personduring this
exercise.
A. 25.9W
B. 50.0w
c. 86.6W
D. 70.7W
E. 100w
48)
o
The systembelow is made of a small ball of massm and a rod of mass9m and length L,
locatedat x - L. Find the position of the centerof massof the systemin the given
referenceframe.
A. xctt: 0.50I, l c u : 0 . 5 0Z
B . x c p r : 0 . 7 5 L , lcu :0.20 L
C. xcu :0.20L, lcu :0.75 L
D. xcu :0.45L, lcu : 0.90L
E. xcu :0.90L, lcu :0.45 L
A 3-g particle moves subjectto the force associatedto this potential.No other forces act on the
particle.
t20
t
/
r
I
/
100
/
/
80
\
U (J)
60
/
I
/
I
I
40
,\
/
\
20
\
\
,/
,/
\
\
./
7
\
/
./
6
x (m)
t0
t2
Theparticleis released
from restat x: 10m. Whatis the maximumkineticenergyof the
particle?
A . I OJ
B. 2OJ
C.3OJ
D. 5OJ
E.6OJ
50)
/
/
\
\
49)
/
Find the x componentof the force at x - I I m.
A.0
B. +7.3N
c. -7.3N
D. +30N
E. -30N
6
5I )
Considerthree forceswhosemagnitudesdependon time as shown below:
Which of the following relationsis correctabout the magnitudeof the impulse?
(NOTE: All three graphsare shown with the samescales.)
A. J1> Jc > Jn
B. J1> Jn : Jc
C. J1:Jn>Jc
D. Js> Jc> J,q
E. Jg > J,q,> JB
s2)
l|_
I
Two massesare on a frictionlesstrack with initial velocities as shown. If there is no loss
of kinetic energyduring the collision, what will the final velocities of the larger and
smaller massbe?
V=O
lo [.q
A.
B.
C.
D.
E.
vroke: -10 m/s, v5ks: -10 m/s
vloks: -10 m/s, vsks: +10 m/s
vroke: -10 m/s, v5ks: +20 m/s
vroke: -20 m/s, v5ks: +10 m/s
vloks: -20 m/s, v5ks: +20 m/s
53)
Two massesapproachthe origin as shown
and undergoa completelyinelasticcollision.
The resulting combinedmasshas a final velocity
Vr : urJ. What ratio of the magnitudes
of Vai and isi can lead to this result?
lnAi
l/lnBi
I:
l-oo
A. 3.8
B. 1.6
c. 1.0
D. 0.6r
E. 0.27
r/
hp
Vri
EXTRA CREDIT
54)
A 50-kg weight is to be pulled up with a rope and a pulley. The pulley is a solid cylinder
of mass 70 kg and radius 0.25 m and rotatesabout a frictionlessaxle. To raisethe weight,
a personneedsto make the pulley turn with a crank of negligible massand length L. The
maximum force that the person can exert on the crank is 800 N. Determine the minimum
value of L required for the weight to have an accelerationof 2.0 m/s2.
A . 0 . 1 2m
B . 0 . 1 8m
C . 0 . 2 1m
D. 0.27m
E . 0 . 3 1m
e\
\:i