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PHYSICS22I
FALL 2OO5
EXAM I
Name (printed):
ID Number:
SectionNumber:
RecitationInstruction:
INSTRUCTIONS:
Put away all materialsexceptfor pens,pencils,erasersand your calculator.
ll.
This l20-minute exam contains30 equally weighted multiple choice problems
worth a total of 85 points (75 points + 10 extra credit points).
ul.
In marking the multiple choicebubble sheetuse a number 2 pencil. Do NOT use Ink. If
you did not bring a pencil, ask for one. Fill in the appropriatecircles completely. If you
needto changeany entry, you must completelyeraseyour previous entry. Also. circle
ygur answerson this exam.
iv.
Carefully ready eachproblem and its five possibleanswersbefore beginningto 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 ex€un,be sure that 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 scratchpaper that you used for the exam, in your folder and
return the folder to your recitation instructor.
viii.
No cell phone calls allowed. Either turn off your cell phoneor leave it at home.
Anyone taking cell phone calls must leavethe testing room and will not be allowed to
return.
GOODLUCK
l.
For the vectors shown below, which of the following is true?
A . 7 - E<A - e<A - D
B . 2 . 8- 1 . e<1 . D
c . 2 . 8- l . e =i . D
D/
t
C
7
.a
7
( D . ' A . B_ A . C> A . D
E . A . B > A . C> A . D
,l
/ /
^l 7
.a /
,
B
7
*f
J ?
/
7
A
2. A coin is tossedin the air, leaving the hand at 1.5 m abovethe ground. It reachesa maximum
height of 2.0 m abovethe ground, and then falls down and hits the ground. How much time
doesthe coin spendin the air?
A. 0.32s
B. 0.64s
A-0.84 s
((p/ o.e6s
E . 1 . 3s
3. At the maximum height of its trajectory,which of the following is true for the y component
of the velocity andy componentof the accelerationof the coin? (Take the positive y axis
pointing up)
A. v,,) 0: a,,) 0
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ir.o
C. vy:O; oy:O
D. vy<0; oy<0
E. vy<0; ey:O
4. Fred kicks a4l}-gsoccerball that was initially at rest on the ground at an angle of 45o with
respectto the horizontal. The ball hits a wall 6 m away from Fred, at a point located2 m
abovethe ground. What was the speedof the ball right after the kick? (Neglect air
resistance).
A. 4.3 mls
B. 6.3 m/s
-4\6.6 m/s
\Ue.4mts
E. ll.2 m/s
5. During the time the soccerball in problem #4 is in the air, which of the following is true?
A. Its potential energyremainsconstant.
--8. Its kinetic energyincreases.
mechanicalenergyremainsconstant.
Glts
weight of the ball doesa net positive work during the trajectory.
Yfhe
E. None of the above.
6. Which of the following graphscorrectly describesthey-componentof the velocity of the
soccerball in problem #4 versustime?
7. JenandLisa aretwin sisterseachwith the samemass.Theysit on a meny-go-round
thatis
undergoinguniformcircularmotion.Jensits I m awayfrom the center,while Lisa sits2 m
awayfrom the center.Lisameasures
on herwatchthatit takesher4 s to completeoneturn.
Whatis Jen'sangularspeed?
A. 0.25rad/s
B. 0.79rad/s
@l.6radls
D. 3.1radls
E. 4.2 rad/s
8. Comparethe magnitudeof the net forceon Jenandthenet forceon Lisa:
A'
Fr"n-- l
D
4 t' r;s
l _
@t"" = ; r r i u
c. 4"n= 4-io
D. 4"n= 2 F r r
E' F,^ = 4Ft;"u
9. A 70-kg person standson top of a box which is insidethe cabin of an elevator.The elevator
has an upward accelerationof 5 m/s2.What is the magnitudeof the force exertedby the box
on the person?
A. 336N
786N
A
( c.) 1036
N
Y
The answerdependson whetherthe elevatoris moving up or down (i.e., the direction of
velocity).
E. The answerdependson the massof the box.
10.The reaction(or third law) pair to theperson'sweightis a force:
A. on the box by theperson
the elevator'sfloor by theperson
zAon
the Earthby the person
\yon
D. on the personby the box
E. on the personby the elevator'sfloor
I I . A lO-kg bag is pulled along a rough horizontal floor by two constant,horizontal forces of
15 N each,that make an angle of 60' betweenthem (seefigure below). The bag is initially at
rest and moves at 4 mls after being draggedfor l0 m. What is the work done by Fz?
(
A 75J
8 . ) 1 3 0J
-u.
150J
D. 640J
E. 980J
Fr:l5N
(Top view)
F z : 1 5N
12. For the problem above,determinethe coefficient of kinetic friction betweenthe bag and the
floor.
0.15
0.18
0.27
0.31
0.41
13. Three identical blocks of massm areconnectedas shown below with ideal, masslessstrings
and an ideal, massless,frictionlesspulley. The force of friction betweenthe blocks and the
horizontal surfaceis negligible. The systemis released.
Which of the following is correct?
-*R
<T2amg
g$$$$$$$ )n
B. Tr < Tz: mg
C. Tt: Tz: mE
D. T1>Tz: mg
E. T1> Tz> mE
14. DetermineT1 for m : 1.0 kg
@r.3N
B.
c.
D.
E.
6 . 5N
9 . 8N
1 0 . 3N
1 2 . 4N
I 5. A 2-kg block slideson a horizontal floor towards a spring with constantk : 1000N/m
attachedto a wall (seefigure below). The spring is parallel to the trajectory of the block, and
perfectly aligned with it. The coefficient of kinetic friction betweenthe block and the floor is
0.5. The block hits the spring and compressesit2.5 cm before stopping.What was the speed
of the block when it came in contact with the spring?
m:2kg
A. 0.13m/s
B. 0.26mls
C. 0.56m/s
@0.75mls
E. 0.98m/s
k: 1000Nim
16. The first graph showsthe potential energy U(x) for a particle moving along the x axis.
Which of the other five graphscorrectly gives the force F exertedon the particle?
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17. The diagram representsthe straightline motion of acar. Which of the following statements
is true?
u(m/s)
12
6
The car accelerates,stops,ffid reverses
A
( BJThe car acceleratesat 6 mls" for the first 2 s
Y
The car is moving for a total time of 12 s
D. The car deceleratesat 12 m/s2for the last 4 s
E. The car returns to its starting point when / - 9 s
18. A boy pulls a wooden box along a rough horizontal floor at constantspeedby meansof a
force ^P as shown. In the diagram,.fit the magnitudeof the force of frictio& Nis the
magnitudeof the normal force, andFr is the magnitudeof the force of gravity. Which of the
following must be true?
.Fr: force of gravity
ir fri.tional force
.fft oot*al force
A. P -f andN: F,
:fandNrFr
^ - E
A . P
r
qg)f
>.f *'d N < Fr
V P>fandN:Fr
E. None of these
19. A personwalks south with a speedof 2.5 m/s. If shewalks onto a moving sidewalk that
itself moves northward with a speedof I m/s, it takesher a minute to get from one end to the
other. How long would it take her to get from one end to the other if the speedof the
sidewalk is doubled and its length halved?
A.30s
B. 60s
@oo'
D . 1 2 0s
E. 240s
20. A mass,M, moveson a frictionlesstrack,thatincludesan inclinedplaneanda loop-the-loop.
If theradiusof the loop is R andthe inclinestarts4 R abovebaseof thetrack,whatis the
normalforceexertedby thetrackon themassat thetop of the loop?
A.0
B. lMg
A2Me
(D)3
Mg
E 4Me
L
2l . Aboat has a water-speedof lVl : 14 m/s. It travels
on a river that has a current of l5 m/s. The river is
L meterswide. Point B is directly acrossfrom the starting
point of the boat, and point A is L/, metersupstreamfrom
/5
point B. Which of the following statementsisfalse?
t:
A,
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3
A'
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tt
c
A. The maximum speedthat the boat can have with respectto the banks of the river is29
m/s.
B. The minimum speedthat the boat can have with respectto the banksof the river is I m/s.
€\
the correct choice of O the boat can reachpoint B.
nwith
D. No choice of O will allow the boat to reachpoint A.
E. If e : 0 the boat will reach a point C.
/ /
22. Whatratioof L
M2
/
/
/
is neededso that everything can be at rest?
Treatpulley andropesetsasmasslessand frictionless.
A.3
8.2
c. I
\ l/2
L EJI/3
\-:=z
23. A massslides down an inclined plane and smoothly changesdirection to motion along a
horizontal surface. Let the plane be frictionless and let the coefficient of friction betweenthe
massand the horizontal surfacebe pr: 0.40 and pr : 0.30. The figure showsfour possible
inclines (A-D). After sliding down which incline will the massslide the furthest on the
horizontal table?
-z-\
(
:
A.A
B . B
C . C
D
_ _ _
U n
-\
I
E.)Each incline resultsin the samedisplacementalong the horizontal surface.
24. A massis attachedto a rope that is 2.00 m long.
The rope is attachedto the ceiling. The mass
and rope form a conical pendulumwith the mass
moving in a horizontal, circular path. If the rope
makesan angle of 25.0" with respectto the vertical
(as shown), what is the speedof the mass?
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B.
C.
D.
E.
1.97mls
2.88m/s
4.43mls
6.17mls
Answerdependson the valueof the mass.
I
_
25. For *.M.M,
in whichcase(s)is thenet forceon the
right-mostblockthe largest?
A. I
B.2
c.5
D.4and5
( E.Yland3
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\=/
l.
2.
3.
4.
;1 t\
26. An object's height as a function of time is given by
y ( t ): 1 4m + ( 2 73 ) t - Q 4 ) t '
S
S
-
Whatis thehighestpointthis objectreaches?
A. 6.75m
B. 27.0m
C . 3 9 . 0m
A, 196m
(SJNone of the above
27. Which of the pairs of vectorswill give the largestresultantvector pointing out of the page?
n=Lte*qi'
:
\=
C
\
*t
^
3t
l
A. B x A
B. B x e
C. e x D
D. A x B
t
t
\/
_
l
a .
l
O\]T OF
PNG€
Dxe
of this disk to
28.A disk is 62 cm in diameter.If we wanta point on thecircumference
an acceleration
experience
of approximately104m/s2whatconstantspeeddoesthe point
needto have?
A. 787m/s
B. 557m/s
A_78.7 mls
kD/55.7 m/s
E None of the above
0
29.lf we could take the work that gravity doeson a 20 kg massas it drops 100 m and usethe
energyto light a bulb rated at 30W, how long could we havethe bulb lit?
A. A little over a minute
ll minutes
@About
Y Approximately an hour
D. Between l0 and I I hours
E. Over a day
30. A projectileis shotinto the air from a flat, horizontalplanewith a speedof l0 m/s. What
anglefrom thehorizontalshouldthe initial velocitybe suchthatthe projectilehits the ground
6.0 m from its launchingpoint?
A. Only 18"
B. Only36"
C. Only 72"
AOnlY8l"
\ry Either 78"or 72"