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Unformatted text preview: 99"??? 2‘1 Physics 124 — Analytical Physics '
SECOND COMMON HOUR EXAM
Monday, Apr. 5, 2010 => <= SIGN HERE NOW: The exam will last from 9:40 — 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
ﬁll in the empty circle for a blank, then enter your ﬁrst name, another
blank, and ﬁnally your middle initial. Under STUDENT # enter your 9digit RUID Number. Enter 124 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 multiplechoice 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 earth’s surface 9 = 9.8 m/sz, usaundm W
m m/sv pair R5 kg/m3) Istickarradabautend = and IO =
1X10“12 W/mz. 1. A 5 kg block is hung from a wire of radius 0.8 mm, cross4 sectional area
5x10”7 m2, length 2.2 m, and Young’s'modulus 2x1011 Pa. How much ~
does the wire stretch? Choose the closest answer. a 0mm . _ FL/A _ {—160  5‘ «Wham _
Y We ‘7’ M ‘ ‘97:" ~——“5——.,—.—5 c) 2mm ° 2): I1) Pa ‘5‘“? m d) 3mm _ e) 4mm ' TO‘DOMM 2. The speed of a mass on a spring varies with time as vi} = 4 (m/s) sin(3t).
The spring constant is 2 N/m. What is the total mechanical energy of the . .2 a
mass on the spring. 4r: Sm (wt\ ~? A = 545m
a) < 0.2 J ‘  Z . 2
b) intherange0.2—0.4J E=K+U=lkA =__l_* 58$ A
c) in the range 0.4 — 0.0 J 2 2‘ W‘ (3
d) in the range 0.6 — 0.8 J __ H,
(e) >0.8J). ’ﬁj’kLZ—J
3. The ﬁgure shows the position (top), speed (middle), and acceleration (bot—
tom) of a mass undergoing simple harmonic motion as a function of time.
The four vertical bars indicate (from left) times t1, t2, t3, and t4, respec
tively (time increases as subscript increases). At which time is a: > 0, v < 0,
and a > 0? '
t1 t2 t3 ‘t4
a) $1  I : :
C) t3 V M
d) t4 0 M
. . . : :
4. A mass m on a spring of constant k undergoes simple harmonic motion of
amplitude A. At what position is the speed of the mass half of its maximum
speed? .
a) 33:0 Art—wAslmLot 0’W=wA
b) a: = A/x/i ~ ‘ 0
c) rc=A2 SﬁméJt\=~—li v> wh=ar656h12=230 e) a): Awisob : Mls
0f; ('0 {1150M .. I
Which pendulum listed below has the longest period? T ~ 2” —— lM cl
a simle endulum, mass M on massless string of length l g ) physical pendulum, uniform rod of mass 2M and length l ) simple pendulum, mass 2M on massless string of length l / 2 ) physical pendulum, uniform rod of mass 4M and length l / 2 ) Period is independent of mass, so simple and physical pendulums of
length l have equal longest periods. Which is true about wave motion? a) Particles in the medium move transversely. b) The speed of the particles and the speed of the wave are never equal. c) Physical phenomena generate either longitudinal or transverse waves,
not both. ' d All waves require a medium to propagate in.
e) None oft e ot ers.\ A sound wave in air has wave number 2 m”. The speed of sound is w 340
m/s. What is the frequency of the sound wave? ai Cannot be determined from the information given.
W fU’:‘i,3  L”) : J» c) 170 Hz K “" 2" 2n, 5 In
(1) 340 Hz “ 2w
e) 1070 Hz A traveling wave in a rope is described by the equation y(m, t) = 0.2 :11 cos [:3 / (0.4 m)+ t/(0.5 Which of the following is true? k f\>
: (£95 ‘l'LO
a) The wave length is 0.4 m. V A ( x _  A, 4 n
b Thefre uencyf=2s_:. kzallla,“ w: 055 :25
c) The frequenc w = 2 s .
d) The wave is traveling to +m. : 1,3 =
e) The speed of the wave is 1.25 m/s. In“ K 0‘8 “93 A traveling wave in a region near the origin is described by y = 6/ (6m +
4t  2). What is the speed of the wave? ( al 0.67 to —m 5' 6X +Attww$lc b) 0.67 m/s, to +m c) 1.5 m/s,to—m bAy +AA‘E :0 d) 1.5 m/s, to +13 4 m
e) 4m/s,to—m 4].: M, —... “gtO,é7 6 AL: 10. A pulse travels in the +33 direction, With displacements in the = +3; di
rection, along a rope under constant tension. The pulse is initially in a
part of the rope with mass density ,u kg/m, but it reaches a point Where
the rope mass density suddenly changes to Zn kg/m, and is at least partly
transmitted. Which is true? a) The relected pulse has +y dis lace'ment. c) There is no relected pulse. d) The direction of the displacement of the reﬂected pulse depends on
the numerical value of a. e) To conserve energy, the reﬂected and transmitted pulses must have equal magnitudes. 11. A rope has mass density 0.1 kg/m. A traveling wave on it is described by
the equation 3,: = 0.1 cos(x/4 ~— t) (all quantities in mks units). What is the
power transported by the wave? a) <O.1mW P : :5er
b) in the range 0.1  1 mW V: Am(m~chB=> K— 4 d in the range 10100 mW k \L,’ . L
e) >100mW sz—ymgx 5‘ (owl, 12. The speed of sound in air is about 340 m/s. The density of air is about 1.2
kg/m3. What is the bulk modulus of air? a) < 102 Pa 43* = l 3’—
b) in the range 102 ——> 103 Pa P
c) in the range 103 ——> 104 Pa E z r) ,Dﬁg (.4; (0 Spa (:1 in the range 104 —> 105 Pa
e) > 105 Pa 13. Your friend is 10 m from a speaker, and hears a 70 dB sound from it. You
are behind your friend, 100 m from the speaker. What intensity sound do youheuc“?
a) 50 dB 1% Jz 1;; h [2:
b) 60dB r If r?
c) 70dB ‘
d) 80dB n z
e) 90 dB Ifﬂ ~93
r l _
pie] = \UéséogEi. “all” 14. Consider the picture shown of the traveling sound wave generated by a
plunger. Which of the following statements is correct? a) The wave has different
amplitudes at points P
and Q. The wave has the same
amplitude at points P
and Q, but the oscilla—
tions at the two points
are 1 / 2 cycle out of phase. c) The wave has the same
amplitude at points P
and Q, and the oscilla—
tions at the two points
are in phase.
d) The wave has the same
amplitude at points P
and Q, but the oscilla—
tions at the two points Plunger oscillating
are 1/4 cycle out of phase. in SHM e) The wave has the same
amplitude at points P
and Q, but the oscilla—
tions at the two points
are 1/8 cycle out of phase. Wave. speed 15. A 1000 Hz sound has intensity 1 mW/mz. How loud is the sound, in dB?
It might help to know that IO = 1x10'12 W/mz. a lOOdB
b 90dB .. 3E : qu= 0
«dB—[DJBZOSIO (045693 44?:
d) 70dB
) 60dB 16. 17. 18. wax/<2.
The amplitude of a spherical soundm drops by a factor of 3 when it travels from point A to point B. What is the ratio of the distance between
the speaker and point B to the distance between the speaker and point A? a) This is a trick question — the amplitude is constant. b) 1/9
Clhlif £15 2 EB: : .L r?” :L 2;
AA ‘72», 33 Va A police car with a 500 Hz siren is heading north on NJ turnpike at 35
m/s. You are heading south at 25 m/s. What frequency do you hear for
the siren? Take the speed of sound in air to be 340 m/s. a) <440Hz {a ’9 (04’0"; M's: ,BSw/s
b) 440—480Hz = o _ m
c) 480—520Hz 4””); “5325 /5
d 520560H
&: mm
l° slurs; 5 What is the angle of a shock wave made by a plane traveling at 1.3 times
the speed of sound? a) 38° = 0.66 radians A = “I __L.
b) 44° = (1.3)~1 radians 5 M!" g c 50° = 0.88 radians
75° = 1.3 radians b4 e) There is no shock wave at that speed. ...
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 Spring '08
 Madey
 Physics

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