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Unformatted text preview: Physics 140 Winter 2009: Exam #1 Please print your name: Please list your discussion section number: Please list your discussion instructor: Instructions 1. Fill in your name above; version number can be found at the bottom of the page 2. This will be a 1.5 hour, closed book exam. The exam includes 20 questions. 3. You may use a calculator, please do not share calculators 4. You may use one 3”x5” note card with notes and equations you think may be useful. You can write on both sides of the card if you like.
5. You will be asked to show your University student ID card when you turn in your exam. Mike Melnichuk 1 024 34
1 025 112301
i 026 12:30 Wayne Lau 004 89 005 9—10 006 10—11 012 34 014 12 015 2—3 Dave Winn 008 910 009 1011 Timothy Cohen 010 89 011 9—10 Catherine Home 016 12—1 01? 1—2 018 23 E Ross O’Connell . 023 23
3 Vivek Narayanan 5 019 12
5, 020 23 021 34 Version 1 Page 1 1. The system shown remains at rest. The coefﬁcients of friction between the block and the
plane are: lug = 0.75, pk = 0.5. What is the magnitude of the force offrietion on the
upper block? Use the following to answer questiori 2: .__ X M
A system of two cables supports a ISON ball as shown. 2 __ M m} 5.“ Q9
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2. What is the tension in the horizontal cable? _ a W
A) 300 N {a “ ‘ '2' 3 00M
B) S. ’1 C0
260 N
D) Elias? ﬁ[email protected]‘—? =6)
E) 17'0 N
’V 9.6 O N Version 1 Page 2 3. A heavy steel ball B is suspended by a cord from a block of wood W. The entire system
is dropped through the air. Neglecting air resistance, the tension in the cord is:
A) the difference in the masses of B and W
B) the difference in the weights of B and W C. the weight ofB
' none of these 1%. qc{$‘ 0"? {W ﬁndj?
mp (Um? SE2 Thwm:“”89
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$3133“ Mvath‘kaa 4. A car moves horizontally with a constant acceleration of 3 mst. A ball is suspended by
a string from the ceiling of the car; the ball does not swing, being at rest with reSpect to
. What angle does the string make with the vertical? A) 43:;
B) 35°
C) 52"
D) 73°
E) Cannot be found without knowing the length of the string Version 1 Page 3 Use the following to answer question 5: Two blocks rest on a horizontal frictioﬂess surface as shown; The surface between the top and
bottom blocks is roughened so that there is no slipping between the two blocks. A 30N force is
applied to the bottom block as suggested in the ﬁgure. Kb?” 6%: .___H\ 5. What is the force of static friction h'etWEEn the t0p and bottom blocks?
A) N “ a... I A
B 5 N E F “I: g C) N ‘“ l S— K‘j Q
m» 60*“ a / t“
I 'I N G E) zero newtons Use the following to answer question 6: A lOOO—kg Jeep travels along a straight 500111 portion of highway (from A to B) at a constant
speed of 10 mfs. At B, the Jeep encounters an unbanked curve of radius 50 m. The Jeep follows
the road from B to C traveling at a constant Speed of 10 mfs while the direction of the Jeep changes from east to south: I I Version 1 Page 4 6. What is the magnitude of the frictional force between the tires and the road as the Jeep
negotiates the curve from B to C? A) 10000N ' L B 1000N ZF’Q“ “V 2; gooom
D) 20000N j“ V E) SOOON 01/ :9 Q0”;
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Use the following to answer question 7: o D Q Qp mg g C Mi ~—~‘=> amissmile”'" " 2 F1 2 135 ~ 017‘ ‘3 O .AT 1‘. ER: T“WI“3:O lee rzwﬁ 7. In a homework assigmnent you computed the acceleration of block 1 under the
assumption that no force of friction acts on block 2. How large a force of static friction
would be needed between block 2 and the table to prevent the system from moving? D) f3 = 0.5 mg
E) Impossible to say, since we don't know the coefﬁcient of static friction. Version 1 Page 5 8. One of the triggers of the 30 years war in Europe was an event called the "Second
Defenestration of Prague". The citizens of Prague threw several representatives of the
Holy Roman Emperor out ofa window 16 meters above the ground. The
representatives landed in a pool of horse manure and survived the fall unharmed.
Assume that the pool of manure was 1 meter deep and estimate the force exerted on one of the falling representatives by the manure. N { O k I 6
A)_..J__X__l_9:lj~x I m M 0 OJ ,. M 2 q I 
no” 5 ~>+o V: = U: + 51:3 5" gran.3";
\ x c
J“: &a(4 *JD) 1x 10' N \ O R‘ ro “(/5 “L
° mg E2 1x10°NC = 3QO.sf/sa
.3 ': (,0  O
°~ a +1“ MW": v: + as cine See's F .. Mail 9. Dr. Evil jumps out of an airplane without his parachute. Minime grabs two parachutes
m { and jumps after him, hoping to save his life. Given that Minime is an exact replica of
(9 0°C) N Dr. Evil but with all relevant length dimensions reduced by a factor of eight, what will N r
I Q [0% happen? _ ‘
0" ‘3 A) Minime can catch Dr. Evrl if he lets go of one of the parachutes.
a». 52.151! B) Minime will catch Dr. vil if the plane is high enough above the ground. (
. .3 Ir 0 “t M ill catch Dr. Evil if the mass of the two parachutes is big enoug . 3 F“!
a . . m
l‘ 511 catch Dr. Ev1l. _ HI _ ad start. ‘ 63"“
w/ Cur. regale1 cg w/c; air rem: atﬂw 3
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2 was 1 a...) : cm... .s = we UW‘H, QVlf : 8 VT‘UM , “15.40 Mr‘ﬂr‘  M WHO’S 144 a. § 5 he <32 “inft UP
10. Suppose you turn on the light in a cheap motel and see a cockroach scurrying directly
away from you at a constant speed 1.40 mfs as you move toward it at a Speed of 0.740
mis. If you start a distance 0.860 m behind it, what minimum constant acceleration
would you need to catch up with it when it has traveled a distance 1.40 m, just short of
safety under a counter? (SD —'> “'0 o = C” '7 4 m ,5 AHQOSmfsz MQ j K :O,$/g+t.9)u1
CB) 3% 5 ° ‘ lidﬁéms ’ Marl“(wté
D) It can't be done, the cockroach is just to fast. t i
E) 9.81mis2 X :1”; m
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g WWI... _______ _____*____ :2 Ox 2; g, O‘i w/s
)(c :2 Vat ck t Version 1 Page 6 {Eisec 1].. A 4kg block and a 2kg block can move on the horizontal frictionless surface. The
blocks are accelerated by a +12—N force that pushes the larger block against the smaller one. Determine the force that the 2kg block exerts on the 4kg block. +12N .. o _. = . C\
“3 (:39 2 Em '— ‘Q‘ N ékj
A) UN q = t; “4/31
Bl... . o .
D :2N #54}.
E) —4N a  _ __ _. ,1 H
Canal 2 F "‘ Q‘Gl’fil' ‘\ e ‘W 12. A 0.75kg ball is attached to a 1.0m rope and whirled in a vertical circle. The rope will
break when the tension exceeds 450 N. What is the maximum speed the ball can have at
the bottom of the circle Without breaking the r0p e? A) 32 mis
B) 16 1113’s E) 12 Infs \LW v r— : (“Fng)
if] m W
3&4w/s E
Wok“ Hj<¢
so Lilo“ GM Version 1 Page 7 Use the following to answer question 13: Two vectors, A and B, are added together to form the vector C = A + B. The relationship
between the magnitudes of these vectors is given by: C,f =' O Cy = A sin 60" + 8 sin 30° AX and A}, point in the positive x and y directions, reSpectively. 13. H e magnitude of A compare with that of B?
A A = 1.7Bi""\
.B) A = 0‘ 8.
< C A=O.7’B £31423 BC¢J5EO ’3 Accﬁéo E)A=0.SB _ (0330 Ezra; __ _ .
’4‘ B cosso‘ mar “BER/[’13 14. A particle moves along the x axis according to the equation x = 612 where x is in meters
and t is in seconds. Therefore:
A) each second the velocity of the particle changes by 9.8 mi’s
B) the particle follows a parabolic path
C) the acceleration of the particle is 6 mfs2
I cannot be negative
E) none ofthe a UV L‘rf f
if 5 ﬁre fﬁvﬂ, X
«‘7 {g ‘ [taQ Version 1 Page 8 15. A boat is traveling upstream at 14 mph with respect to a river that is ﬂowing at 6 mph
(with respect to the ground). A man runs directly across the boat, from one side to the
other, at 6 mph (with respect to the boat). The speed of the man with respect to the E .
A 131% w .
B) Umq’t) lacﬁtT an ‘0 LHPLI C) 18.5mph
D) 21 mph €
E) 26mph V r: «(all
7 .. 17“ ~17 ife  < "3
“(‘3 ‘— ﬂ'cl ‘3er M
Pea “WEE—£53: 2 {Crow/of?
v/ z "germ
Ae .. a ﬁg Ur; = la 1. =— 399,01,
“{9} '" V *V w ~> "3
Wt": F “(B W 16. An 80 kg circus clown plans to climb a rcpe as part ofa comedy routine. The clown
starts at rest on the ground next to a 60 kg box full of coconut cream pie. The rcpe goes
over a pulley that is three meters above the ground. The other end of the rope is
attached to the box of pie. What acceleration must the clown have to guarantee that the
honofpiennu reach the pulley 1 second after he begins climbing? a]? agree)
) "91'81mrs2 C) 1.00 m/s2
D) 0.00 m2
E) 3.17m2 Version] Page9 Tr q 8 N _. —.2
17' If‘A+B 2A2+BZ,then: A) an le between 2 and E must be 60"
B) either 2 or B must'be zer ) :4 and 8 must be parallel and in the same direction D) :4 and 3 must be arallel and in opposite directions
E) none of the above is true
 _ q f( 2 74 I5 Kerf {LQ 18. An airplane pilot wishes to ﬂy due west relative to the ground. A wind 0f74.0 kmfh is
blowing toward the south. If the airspeed of the plane (its speed in still air) is 320.0
kmfh then what is the speed of the plane relative to the ground? A) 328 km/hr
B) 2461(me _,_> .__\> c)___.32.0k1mm V : U — U _ é 3
I” '
bee/ﬂue Him? at? [£679
N t . ' “9
*CJ Cirif‘ +0 $16 Version 1 Page 10 19. The diagram represents the straight line motion of a car. Which of the following
statements is true? ‘ Cl 0 {<32 Wf
vim‘5} l S
12 — — , ‘ ‘
( n Farsi o Nlouf
a (£3. attract Waltz
as) ' 5 9' C or we.)
Ai The car accelerates, stops, an es he car accelerates at 6 mi’s2 for the list 2 s The car is moving for a total time of 12 s
D) The car decelerates at 12 Ini’s2 for the last 4 s Q 3 H I 3 L) E) The car returns to its starting point when t = 9 s Cqu CCU VIPUnﬁt“ “10.45 {0 w ' ‘ .
Use the following to answer question 20: 0” Go I I! S Slé’v 74' /O(;‘f f 3 Two SN boxes are attached to opposite ends of a Spring scale and suSpended from pulleys as shown. 599(Q MSG/‘63 {TC/(9’5? deﬂe'o ,9 20. Suppose that the system were placed in an elevator that accelerated downward at 2 mfsz.
What would the scale read? A) 2N
B) ON
C) 6N
D) 8N
~_____M____../ Version 1 Page 1] ...
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 Physics, Friction, version, Dr. Evil

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