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Unformatted text preview: excitesÂ» Physics 124 â Analytical Physics
FIRST COMMON HOUR EXAM Monday, Feb. 21, 2011
Professor Ron Gilman => <2 SIGN HERE NOW: The exam will last from 9:40 â 11:00 pm. Use a #2 pencil to make entries on the answer sheet. Enter ID information items 25, now, on the
answer sheet before the exam starts... In the section labeled NAME (Last, First, MI.) enter your last name, then
ïŹll in the empty circle for a blank, then enter your ïŹrst name, another
blank, and ïŹnally your middle initial. Under STUDENT # enter your 9~digit RUID Number. Enter124 under COURSE; you may ignore the section number. Under CODE. enter the exam code given above. During the exam, you may use pencils, a calculator, and one 8.5 x 11 inch
sheet (both sides) with formulas and notes. There are 18 multipleâchoice questions on the exam. For each question,
mark only one answer on the answer sheet. There is no deduction of points
for an incorrect answer, so even if you cannot work out the answer to a
question, you should make an educated guess. At the end of the exam,
hand in the answer sheet and this SIGNED cover page. Retain the
exam questions attached for future reference and study. When you are asked to open the exam, make sure that your copy contains
all 18 questions. Raise your hand if this is not the case, and a proctor will
help you. Also raise your hand during the exam if you have a question.
Please have your student ID ready to show to the proctor during the exam.
Possibly useful information: at the earthâs surface 9 = 9.8 m/s2, G =
6.67'><10~11 Nm2/kg2, mam}, = 6><1024 kg, rem}, = 6.4x106 m, [hoop = mr2,
Isoliddisc = (1/2)m7"27 Isolidball = (2/5)m7n27 and Istickaboutend = Two masses hang from massless ropes attached at different radii to a lkg
pulley. The left mass, m1 2 5kg, hangs from a radius of 0.2 m; the right
mass, m2 = 10kg, hangs from a radius of 0.1 m. There is friction between the rope and the pulley. The pulley is supported at its; c.m. What is the net torque on the pulley from the forces acting on it? y 1: ~: MâJâ. ml\ % Coms'xclar 4h: CAMÂ» 9!} 36w; âmar Mina 36m.
(M WWW {bite =D\
2; 3% WW6 Â«9% it, Caveman}
d) 19.6N MA. FL (âtz=WL%VZ\ preMSQ/fe
e) 196N each OâWJLS'. Ms,
2 E5 :0 \ WK "FL:W\1C8 L Your professor puts several objects on an inclined plane. All roll without
slipping down the inclined plane. Which gets to the bottom ïŹrst? a) hollow sphere, radius r ZWZXïŹ Cal/\Ă©ervaâlrlbh j = Kâ\' P 1â CDl/âSl7
b) solid cylinder, radius 7" L O\
c) solid cylinder, radius 27" ( solid sphere, radius 7" 5 ,vâ ...Hiuaâ sped 94 Weym, w *5 e) hollow cylinder, radius 27â L MAWâLb A. z] z OFFM Ă©o+bwl The ïŹywheel of an engine rotates at 10 rad/s with an applied power of 10
W. What is the frictional torque in the the engine? a 0.1 Nm
h c) 10 N~m
d) 100 Nm
e) Cannot be determined from information given.
A
Do 2 {O ~ We. ml? "7%Mlâeswerâwa
cle Wâ W (halls, m m â15 Q
War
\fgvich'ou Tam A 9  \O âŹ5.55 4. A 2.0 kg solid disc 0.5 m in radius (neglect its thickness) slides along a
frictionless horizontal ïŹoor without rotating at a steady 2 m / s. What is the
angular momentum of the disc about a point P on the ïŹoor? a) It depends on where along the ïŹoor P
is ' 2.
b) 0.25 kgom/s c 0.75 k'm7s
m3
e) 8 kgm s IÂ»; _ h mÂ» a, âa, a v8; _. v â> Em.
L = PH; L = ZïŹâPz â2 Va *WâïŹâ â MVâZ âW M32â i V 5::269,
i L T â9 âlâlAe CUSC radiws.
5. Two identical solid balls start from rest at height h. The one on the left
slides without rolling down the left smooth frictionless part of the track
shown. The one on the right rolls without slipping down the right rough part of the track shown, with v = our. The balls hit on the smooth frictionless flat bottom part of the track. What is the ratio of weft/might just before
the balls hit? a) 1 b) 5/ â
mm;
d) 3/2
9) It depends on exactly where
the balls hit. smooth R 2 tâ
'7... . 7. (Q
ââl c l 6. A wire has a 1m long segment of steel (Youngâs modulus =_ 2 ' 1011 Pa)
and a 1âm long segment of brass (Youngâs modulus = 1  1011 Pa), for a
total length of 2 m. The width of the brass wire is two times that of the
steel wire, so the area of the brass wire is four times that of the steel w1re.
When a weight W is hung from the ceiling by this wire, the steel segment
stretches by 1 mm. By how much does the brass segment stretch? a 0.25mm ( , Aeâ
5 p...) A, m _. .._. ~â Â»â 0.5mm
d; Aâ e ZAei Y7. A}
e) 4mm F V A62. 5
7i â 2 <9. L 7. A machine part has the shape of a s31id.uniform sphere of mass 0.2 kg and
radius 0.03 m. It is spinning about ïŹriïŹlionless axle through its center,
but at one point on its equator it is scraping against metal, resulting in a friction force of 0.01 N at that point. Find its angular acceleration. Jan? vim a) 1.2 rad/s2 (Z =xo< W2
Fr \0 A/ c: an? b) 2. Brad/s2
c) 3.6 rad/s2 04 == 2 d 4.2 rad s x 25: ww?â email($345 m
e 6.6 rad/s2 (The gemâ
8. An object is placed at the left end of a 20 kg, 5~m long beam.\It/is supported
at the right end and at a distance 4 m from the right end. How heavy can the object be without the beam tipping over? â
_. a) 0kg . , v ,, zal
b) 13.31% OOMAALLOM. Y; c) 20 kg Taxwee wiâW
@BOEk) .. , .i 0:
e) 80 kg W5?â L3 4 9. A 200âkg Physics Professor, being utterly frustrated with the students?_ reâ
sults, turns into a spherical black hole. Find the professorâs Schwarzschild radius11043 R .. zen ..._. 
5 C2 ($033?â c 110â17m ~2Â§ d) 310â12m "= 37âl0 m e) 1~10â6 m 10. The Martian moon Deimos has a diameter of about 12.6 km and a mass of
about 2X1015 kg. Treating it as spherical, how fast do you have to throw
a ball so that it circules Deimos, 2 m above the surface, so that you can
catch it?
a) < 2 m/s
b) in the range 2 â> 4 m/s
c) in the range 4 â> 6 m/s \
d) in the range 6 â> 8 m/s
) e >8 m/s , (
Rd Mm âE; X osnLĂ©ng 4'6 5
11. Two solid spheres, each with a mass of M = 10139 and radiust = 0.1m,
touch one another. What is the magnitude of their gravitational force of
attraction? Z Vâ Z â D k 2
a UN v FggïŹzzgïŹxlo ïŹgxwl:
) 3 4 NW I (2 m 4% 7 (mm
c . m _ 
d) 6.7w107N â Râ 7â mïŹS's to /(/
e) 9.8m107N 12. Titan, a moon of Saturn, has a 16 day orbital period and an orbital radius
of 1,222,000 km. What is the mass of Saturn? a < 1><1026 kg
m Titan c) in the range (0.1 â> 1) ><1028 kg d) in the range (0.1 â> 1) ><1029 kg e) >1><1029kg .. .233? :> (\3â: artâ:â
T" 43' l 2 (2â\7.â_'Â§ S ZĂ©k
âL M.W\ Wl'1M. 2:. 5MB
3 _â. ââ '\ W~1~W=Grffx M5 6â GT7â 3 Yâ r 13. A satellite with a mass of 10109 was launched into a circular orbit 1000 km
above the Earthâs surface (the Earthâs radius is 6.4 â 106 m, the'Earthâs
mass is 6  1024199). What is the total (kinetic + potential) energy of the
satellite? Take the potential energy to be zero when the Earth and satellite
are inïŹnitely far apart. a) 134083 E ==x4+x> = (CWme)< â3 hams b) 27108.] 2 2tâ
0 â2.7108J 1 2" 2
d) 5.4.10.1 : 4,.7MDâWâQ. 6"â) âof :â 2.72H083
e) â5.4108J i=3 v quuto m 14. A tall cylinder is partially ïŹlled with water. The cross sectional area of the
cylinder is 2 m2, and on top of the water is a lid, tightly sealed against
the sides but floating on the water. What is the change in pressure at the
bottom of the cylinder when several students (one shown) with total mass
200 kg stand on the lid? . , a) There is no change in pressure.
b) 100 Pa
0) 200 Pa â ) d 980 Pa 
e 1960 Pa 15. A rectangular wooden block of weight W ïŹoats with exactly onehalf of its
volume below the waterline. Masses are stacked on top of the block until
the top of the block is level with the waterline. This requires 20 g of mass. What is the mass of the wooden block? b) 10g WaszïŹyi ( 9(WâgâecĂ©lïŹ2
Cm g \m Â»> Liâs amazes
â3 QM 00214333 =90)ng m+002Â„g z 2 W=D.02kïŹ
w 16. In a pipe of radius 0.1 In, the water ïŹow 18 Zhgfs past a certain p01nt.
What is the speed of the water further along the pipe Where it expands to a radius of 0.12 m? WWâ 3 45" A i: âUâZrAz b) 1.7 m/s A l
c) 2.0 m/s v _ *1 _~ {In DA (V W\
.1) 2.4.0. 057, âv. A ~ 2 :5. Â«57.1 e MW 4
L h
e) 2.9 m/s
17. A uâshaped tube has mercury in the bottom, With density 13.6 times the
density of water. 10 cm of water are poured into the right side. How much
higher is the top of the water on the right side than is the top of the mercury
on the left side?
a) 0.7 cm
b 0.8 cm
i 10 cm
e) 136 cm
0017 Or âHie FraSEM/TB Wat/Â«91â Q6, âthe, SW19 W 0
~â 5 ~ x _ r:
Ms. M t; ~ M 1x. Inlâ W = 9;.) st mam  0,14cm 1M k2 (3 m
18. Water in a tube ïŹows at 2 m/s. What is the change in pressure at a point
1 m higher Where the water ïŹows at 1 m/s? Assume the density of water is 1000 kg/m3. a) 43300 Pa \ b)
C)
d) ) e â6800 Pa
0 Pa â the pressure does not change
6800 Pa
8300 Pa P~+ pgâ Hiya)â: Cal/15+
A P : Pm = 42 e (valVA Wt OHM â~â
.%11000%3(443g .( â3â $300 Pq m.â
.â 7. 4â,!â
[email protected]+am. =â~ we; 2r â6â ==' (Dam *0,7ZMIM
c: 4â. Barn 2
2 ...
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 Spring '08
 Madey
 Physics

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