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Unformatted text preview: n4"? I KO
r P"
PHY 317K October 2, 2001 Name:.J§»§si}..&1llmfeﬁ: ...... .. Exam 1 —— Unique number 57820
Instructions: ' Take alternate seats if possible.
0 No notes, textbooks, calculators or similar aids are permitted. 0 Use the scantron answer sheet to provide the answers. Follow exactly the directions how
to mark it. Write your name, SSN, course number, unique number. Sign and date it.
. Mark solutions for all problems. Mark your answer sheet using #2 pencil. Any errors in ﬁlling in your scantron sheet could result in your exam being discarded. N0 PARTIAL .
CREDIT will be given! 0 Assume g = 10 rn/s2 only where it is explicitly stated so! 0 Unless you are ready to leave at least 5 minutes before 12:15 pm, please, stay in your
seats until all answer sheets are collected exactly at 12:15 am. 0 Any questions you may have about the test have to be directed to the instructor —~ no
conversations and/ or collaborative work are permitted. 0 The next page contains some equations and other information that may be useful on
this exam. You may not ask questions about this sheet, however. 0 Use blank sides of the exam pages for notes and calculations. Some Equations for Exam 1 sin30° = 1/2; cos 30° = ﬂ/2; sin60° = VIE/2; cos 60° = 1/2.
For any function of the form x(t) = at", where n is an integer, $11; : mum—1. ' The antiderivative of (t) = at” is 3:71:73“. The deﬁnite integral of f(t) from t1 to rig is j}? f(t)dt = F02) — F(t1), where F(t) is an
antiderivative of f ' A A B = A333, + AyBy + Asz 2 AB cos 6.
If a particle’s position is represented by r = r(t), _dr _d ' a"d_v_d2r
V‘EE 3“ "dt‘dﬂ' For a constant acceleration a, 1
r(t) = ['0 + vot + Eat2 and v(t) = v0 + at where re and v0 are the position and velocity at time t = 0, respectively.
Freely falling objects accelerate dewnwards with g =: 9.8 m/s2 = 32 ft/sz.
Centripetal acceleration for uniform circular motion: a = 112/1“. Newton‘s Second Law: F = ma. Static friction: fs 5 lnaN; kinetic friction: fk = [MN (N = normal force). Answer the following questions: 1. A dart is thrown horizontally aimed toward the center point X of a target with initial (horizontal) velocity 10 m/s. After 0.2 s it hits the target at a point directly below the
point X. How far from the point X does the dart strike the target? (Ignore any effect
of air resistance and assume 9 2 10 III/S2.) a . 3: —Fag+34 vch + Bo
 m
(c) 0.1m E): "'li‘C0)L0«35a+o+o
e . m 2. A car traveling at 3'6 k‘m/ hour begins breaking and stops after 2 3. Assuming a constant
deceleration (negative acceleration) during the breaking, how fardoes the car travel
during breaking? Recall 1 km = 1000 m and 1 hour = 60 min = 3600 s. (a) 5 m (I W x; x61» Vol: + it :Lta‘ m; 1000‘ no x l'bf
@ 101” I ' M" “to 3:553 '
(c) 20 m _ v4: V0 + out .
(d) 80 m — gsabwm' : "3 W5 (6) 160 m 'o: m + Lcha) Beer’s 3.: "5 m/SE “:43 003(3) + @05fo = so 10 : Io Refer to the following statement in each of the next three problems. The position in one dimension of an object is given as a. function of time by x(t) =
20 In — (2 m/s)t + (1 m/sz)t?. 3. The position of the object at t = 10 s is: (a) 22m 100).: 30 — 200) # FUOGJ
(b) 210m : 20—30 Hod (c) 200m : 130 (d) ~100m ‘100 m 4. The acceleration of the _object at t = 10 s is: @2‘11/52 _ V4145): —?_+ 2+.
(b) 3 m/s2 ’ (c) 4 m/s2 Mt) p E (d) 2 rn/s2 (e) 2t 5. . The scalar (or “dot”) product A  B is equal to: The velocity of the object at t = 10 s is: (a) 0 m/s
(b) 21 Ill/S .
@18 m/S Vet):~a+ at
(d) —1 m/s v00) 3 "8+ 20°)
(6) 99 m/s : 20"2 ': r3 Refer to the following two vectors A,B in the next two questions:
A =5i—3j; B=2i+3j. The symbols i and j denote the'unit vectors in the positive a; and y directions, reSpec
tively, of the rectangular (Cartesian) coordinate system. {53'33 ' (a) 15i (h) 0 (e) none of these : @1 (d) 54 IO ‘9 . The magnitude of the Vector A is: : l (b) 14 (e) none of these (a) «1—5 ' (c) 8 m
Illgiiﬁshea)? 5 \g: Q . A 2500 kg airplane moves in a straight ﬂight at a constant speed speed of 500 kin/hr. The force of air friction is 2500 N. The net force from all sources on the plane is: (ED zero (b) 3000 N (c) 2500 N (d) 1000 N (e) 500 N . Two blocks are connected by a. string passing over a pulley. Masses of the blocks are 90 grams and 110 grams. Assuming that the string and pulley are massless, the magnitude
of the acceleration of each block is: (a) 0.049 m/s2 (b) 0.020 m/s2 (c) 0.0093 m/s2 (d) 0.54 m/s2 .98 m/s2
I'oﬂN : {makgjcon QC; 3.3,;
0.: lmxsa
: cmN : 63 N
outs 'FNET LIN I . ﬁwu
i, 0,532}; {0.9 a; .95 5’ t *2;
l. L, f I /_,_
E E73 \{Boc} Refer to the following'situation in the next two prob e c's.
A cannon, which is sitting on the ground in a region where the ground is perfectly
flat and horizontal, ﬁres a cannon ball into the air at an angle of 60 degrees with respect to the horizontal direction. Ignore air resistance. The initial speed of the cannon ball is
200 m/s. In your calculations take g = 10 m/sz. (Hint: \/§ = 1.73.) 10. What is approximately the time of ﬂight of the ball (i.e., how long' is the cannon ball in
the air before hitting the ground)? (a) 8.6 5 wt 2 I73 l: = 173 5 v.1: 200 since"
@173 s (3:113 ~ next) is room's  D ' — aooc ‘51}
(c) 34.6 s or = Bocce.865)
'(d) 12.5 s “frY" + ‘9‘ _ : IT? "Us
(8) 10.0 s (c 11. What horizontal distance approximately will the cannon ball travel before hitting the
ground? 6
Vex : COS (a) 17.3 m _ l 34 6 m — .2006 5' 10011315
d 3460m V
1730m 96'3U00X17.3j 3 [730 m 12. Two masses, m1 and 1712 are connected by a string as shown below. The leading mass
' is being tugged by a force F pointed along the direction of motion. Both masSes have a coefﬁcient of kinetic ﬁiction WC with the table they are being dragged along. What is
the acceleration of this system? Take m1 = 15 kg, 1112 = 5 kg, ,uk 2 0.25, g = 10 111/32. ,. a) 10 ni/s2 4 ‘ “N
2.5 111/52 k (C) 4 III/s2 N : (Boy16) : 200 N
(d) 5 III/s2 I
3
(e) 7.5 m/s2 rx: 90.253300
. : m N . M “at N
r" 1‘ L P I t
in F  : (BOBCOD 13650: 2063.)
.8011QE‘A
S 1
a: '1. mfg
5 <53 6  ‘ ‘ H600 L6
13. A crane operator Ioiﬁers a 4000—lb steel ball with a downward acceleration of 8 ft /52 The tension in the cable is: as s: s95 ' (a) 40001b (b) 1000 lb @30001b (d) 5000113 (e) dependent on the
velocity of the ball 14. An object with mass 10 kg is dropped from a. height of 80 in. What is its speed upon impact with the ground? Take g = 10 m/s2. #33: — léttext‘?) £2; ’6 t: ‘45
(a) 10 m/s (b) 20 m/s (c) 30 m/s 40 m/s (e) 80 m/s xi: 0  new)
: ’LlO mg; 15. A 1,500 kg car moving on a ﬂat road negotiates a curve whose radius is 80111. If the
' c0eﬁicient of static friction between tires and the dry pavement is 0.5, ﬁnd the maximum ‘
speed the car can have without skidding. Take g = 10 m/s2? (a) m m/s 5+m+ic ¥p§c+icm :: can’tﬂileAGe‘ (“C3
(b) 5 m/s' . is= Ln,S)Ll500>UOJ 10 m/S : 7500 N a Va
6‘ 20 m/s  7506 = new )L 55") 5 2 :96 (e) 40 131/3 16. A forward horizontal force of 5 N is used to pull a sled of mass 1 kg at a constant velocity
on a frozen pond. The coefﬁcient of kinetic friction is (take 9 = 10 Ill/S2): sh : FA {if #19,” (a) 0.05 0.5 (c) 0.1 (d) 1.0 (e) 0.2 5 41: 5: man 17. An object is kicked with speed 20 m/s at t = 0 upward along an inclined plane, with 5 : (DUGXM)
inclination of 30° with respect to horizontal. There is friction between the surface of the plane and the object with pk = 1 /\/3. Measured from its position at t = 0, how far will M: Q '5
the object move along the inclined plane before stepping? (Take g_ = 10 111/32.)
(a) 0.5 m ' lk ; (XfﬂMJCiOKgo/s‘ﬁ) 1 '  Vox ::
. " ' i f .
(b) 1 m 33 x a": : Tsihscf = lair i. ‘
. l A x i J i :
(C) 5 m W5 I .1" i ' i l
i g a ,4“ I, j
ax ax V04: BQfInSO :\Q/m(5 I its act£4. “3ch
I 0 _ if, . \ t: QE— '3
26 , of m T’ a: 1!“ 7,5(‘0’ t mise'
 y 10 18. A airplane is ﬂying in a circle with a constant speed. If the radius of the circle is 600 m
 036 a and thecentripetal acceleration is 6 m/s2, approximately how long does it take the
tc airplane to gocompletely around the circle one time? (Recall 11' z: 3.14.)
.2133 (a)13.ls‘~
3V ' _ ’
Jc (b) 93.3 s M C ‘ (2“ X600) c me; = 600 l (C) s — IBOO 1T UL __ “W‘VL—x
_ %OQ ‘ “ g a 00
gm am? @ 62.8 s I ' 6e ms ‘3 e e O .30
r r}  I —\ A
0 / ' _ . . s: '7 O “" 3‘
3:0, m 1 ‘ 6‘20? 5 \l0 ’10 Z L“
n O 4; : 5 = Cl; ; 1‘ 2m '3 E.
g: a; k . I“ a r. 1.10 2: 0420(3) + epdéléll ‘3‘: —5m/S 0= 2.0' 45* 3510 {ﬁgs W 19. A ball of mass m is being twirled around in a horizontal plane by a young child. The
ball is at the end of a string of length R and is moving with constant speed 1:. At the
point indicated by AA, the string breaks, and the ball goes ﬂying ofi‘ in some direction. The ﬁgure below shows 4 possible trajectories the nowunfettered ball could take the
instant after the string breaks. Which of these trajectories does the ball follow? (a) A
@ B
(C) C
(d) D
(e) depends upon the Speed 1; 20. A block of m1 = 3 kg is resting on a table. The block is connected by a light, ﬂexible
string over a light, frictionless pulley to a mass m2 = 1.5 kg that can fall freely. If the
1.5 kg mass is falling at constant velocity and if there is a coefﬁcient of kinetic friction
,uk between m1 and the table, compute the coefﬁcient pk from the information given.
Use 9 = 9.8 III/82 in any calculations. (a) 0 1 ‘Fk: FA
(1)) 10
(c) 10 gammaw) (d) 2'0 (a s) FA: (LS) ‘ L151 2) : $3131») AL: (3.5 21. Which version of this exam are you working on? (a) white pages photocopy
@ colored pages photoc0py Test?) 7 Answer the 20 questions:
1. Density is: a 333.13? (b) a vector (:2) a measure of the weight of a ﬂuid (d) always larger fer a'solid than a liquid (3) none of these '2. A Illtube initially contains a liquid of density 4g/cm3. A diﬂerent liquid of density ' 1 g/cm3 is then peured into one arm of the Untu‘be. The two liquiliS do not mix. If the
second liquid ﬁlls a. column of height 8 cm in the arm Of the Uétube into which it was
poured, how far does the ﬁrst liquid rise in the Other arm of the Utube with respect to its initial “light? The yrescw‘e at A M B
(8 05cm Must in. ﬂu: {Au‘
2: gm 1‘ i. 9 = 4'9‘ “1)
(a) 4cm ‘1: i a» {e)‘ none of these 3. A toy boat ﬂoating in pure wate; (ﬁensity llngem3) a. volumeof 1 liter of
water. Ifthe same toy boatis to a. tank ﬁlled with a liquid of density 2.0g/cm3,
what will be the weight of the liquid displaced by the toy boat? {Hint recall 1 liter =
1000cm3and1kg=10003,andofoouraeW=mg.) ‘ Mtg ' (a) 1 N weight. of glaringX, “Q1434 * MW: Log/4.2 1.0km; lrﬁ/las
b 5N
@ON does M dingo... l iiimu = M3 on; = (0’3 w“: d)20N WM“ = w, ,
(eJ40N 9 in V 3L _ l
= la’xlo"aa elou \ 4. Water ﬂows through a square pipe of varying ewessection. The pipe runs horizontally,
so the water remains at constant height. The velocity of flow is 8 m/s at a point where
the pipe’s sidedimensions are 1 At a point where the pipe’s side are 2 cm, the velocity is: 4F” _ .
‘M The cootumult ﬂingclan ; 5; _
(a) 16 “1/3 I 7 my Av “are
(b fwﬂfﬂ‘. 1 ' ? = faulth 2;: I”.
2 m/s «1r: 2 w/s‘
( 0.5 m/s _——__.
'(e) 0.25 m/s 9. The maxinium velocity of the masssis: (a) 01 m/s Finn The musevwL‘wn u'l «away 10. After the mess is released, how much time will have elapsed when the mass ﬁrst reaches .
the positibn of zero displacement {i.e., Where the is (a) {3.255 The Pasnon ‘11:) ',g aw.“ la)! (b) 3E 5 . z: = L a
(c) % 3 arm at», w: (Lut) (Lo) m,( if) Hm: 1 in = %
(d) %S TH} 54495113: 0 {~31 who“ it 2 7L ' Es ‘t=‘£: a 11. A mass attached to a spring oscillates at a particular ﬁequency. Which of the following
changes would result in a. higher ﬁ'equenLy of oscillation?
_ ' s k
a Use a. larger mass. .[. = _ E
@ Use a smaller mass.
c) Use a spring which has a smaller spring constant.
(:1) Increase the amplitude of the oscillation.
(e) noue of the above 12. What is the wavelength of a transverse travelling wave with a. velocity of 50 m/s and a
frequency of 5 Hz? _ tn ar
mzsoDm ‘U’=+A='> A*T9T: 1a.?
(b) 50.0m
910.011;
5.0111 (e) 29m 50.0 m 17. When ﬁstening to tuningforks offrequenda 440112 and 448 Hz, one hears the following
number of beats per second: (a) 444 41‘ of beats/m «a Hui] : 4H 479.: e
(W333 @3
d)4 (e) 2 18. An ideal gas occupies a. IGﬁter container. At temperature T = 27 °C, the pressure
inside this container is 3 mm. lithe gas is heated by 100 °C, the new pressure is: ’4etm get (an; '. 19V: VIE—r (mam w“ (c) Satin T : 273947: hakﬁ €509 Kw
(d)12'atm z ‘5 9:":
(8) 20am: P 3 a“ a h 3” z 4a“ . ——_.._ 19. The speciﬁc heat of an object is: (a) the amount of heat energy to. melt one gram of the substance
(1)) the amount of heat energ per unit m emitted by burning the substance
(c) the amount of heat energy per unit mass needed to raise its temperature from its
freezing point to its boiling point
(d the temperature of the object divided by its mass _
me °f these The amt a") hat energy [ma umit Mac: u was its tenureM are by IK. 20. A heat engine operates between reservoirs which have temperatures of 300 K and 500 K.
What is the maximum efﬁciency of this engine? T... 3,. I MaximM eff(tau? = L 75:: [;—:. =_ Egg a?
(c) 0.6
(d) 0.8
(e) none ofth‘es'e PHY 317K
November 6, 2001 Name:.§l._m..€7iillman ............ .. Exam 2 — Unique number 57820 Instructions: 0 Take alternate seats if possible.
a N 0 notes, textbooks, calculators or similar aids are permitted. 0 Use the scantron answer sheet to provide the answers. Follow exactly the directions
how to mark it. Write your name, SSN, course number, unique number. Sign and date it. Mark solutions for all problems. Mark your answer sheet using #2 pencil. NO
PARTIAL CREDIT will be given! 0 Assume g = 10 m/s2 only where it is explicitly stated so!  Unless you are ready to leave at least 15 minutes before 12:15 pm, please, stay in your
seats until all answer sheets are collected exactly at 12:15 pm. a Any questions you may have about the test have to be directed to the instructor — no
conversations and / or collaborative work are permitted. a The next page contains some equations and other information that may be useful on
this exam. You may not ask questions about this sheet, however. 0 Use blank sides of the exam pages for notes and calculations. Some Equations for Exam 2 , sin 30° 2 1/2; cos 30° = ﬁ/2; sin 60° = «32; cos 60° 2 1/2.
The work W done by a force F: W = [if F 1 ds, where z' and f represent the initial and
ﬁnal positions, respectively, of the particle. The instantaneous power: P = d—dvg.   . m l 2
The kinetic energy. K M imv . The work—energy theorem: Wnet 2 AK. The change in potential energy U and the work W done by a conservative force are
related by: AU 2 —W. The potential energy U of a system is AU = Uf — U, = —W = — if F($)d:c. Gravitational potential energy AU 2 mg(yf — ya) = mgAy. 2
2 . Force due to a spring: F5 = «km. Elastic potential energy AU = ékx} — éka:
Momentum: p = mv.
In an isolated system where the forces are conservative, U + K = E’ = constant. When the net external force acting on a system is zero P = const. Position of the center of mass: ram 2 ﬁﬂmiri, Where M =: 2mg. . For a solid object of mass M, ram = ﬁ frdm. The impulse J of a force F acting on a particle during a time interval from t1 to 152
is J = f? th. The impulse is equal to the change in the momentum of the particle: J = pﬁnal "‘ pinitial : Ap
For a one—dimensional elastic collision: _m . _2“12_ . _ 2_im_ . _m_2"_m.i. .
Ulf _ mi+mzvlt + mi+m2 v21 vzf _ mﬂ—mzljl2 + m1+m2 02“ For onedimensional motion and completely inelastic collision of two bodies:
mlvl + m2U2 = (m1 + m2)V. Angular velocity: in 2 d3? Angular acceleration: a = fi—‘g’. For a constant angular acceleration, — w = we + at, where mg is the angular velocity at t m 0,
— 915 = qﬁg + wot + éatz, where 450 is the angular displacement at t = 0. For circular motion, tangential acceleration: GT 2 or. Radial acceler.: a3 = 122/?" m w2r. Rotational inertia, or moment of inertia: I 2 f rzdm. — for a solid sphere about any diameter: I = §MR2
— for a solid cylinder about the cylinder axis: I = éM’R2
— for a hoop (a cylindrical shell) about the cylinder axis: I = M R2 0 Torque: 7'" I r x F, so 7' = TFSiDG. For a rigid body7 ‘7' = Id. 0 Angular momentum: L = r x p. L = va sinqﬁ = rpi : 1"va = up : 71mm In
special cases L : Iclr'. For an external torque, 7" = %. o For rotating bodies is AK = %Iw% w 51w? Answer the following questions: 1. A man pushes an SON crate a distance of 5.0 m upward along a frictionless slope that
makes an angle of 30° with the horizontal. The force he exerts is parallel to the Slope.
If the speed of the crate is constant7 the work done by the man is: (a) 61 J (b) 140 J @200 J (d) 240 J (e) 400 J 5m h h= 55:11.90"
0 2 L50, Us: CgGNJ(£.SmJ_ 2. A mass m at the end of a string moves in a vertical circle; that is7 the circle lies in a
plane which is vertical. The bottom of the circle is at y r 0. At the bottom of the
circle the kinetic energy of the mass is just barely enough to get it up over the top of
the are i that is, the mass just barely has enough KE to do a “loopthe—loop”. What
is the tension in the string when the mass is at the bottom of the circle? Hint: Use
conservation of energy. Also, what provides the centripetal acceleration? U=? , K=? (a) mg g, n _ NR
/ \
(b) 2mg m . "iv—a my}
(c) 3mg ,' I‘ T_ 9' r. T‘mg 3 V2
d) 4mg T J i} a _ if?
5mg rub/Ti}. // lémv : "Scar 3
\ i , Tami}: gm?
\i“\uzo,jK=? ‘/' l’a 9W2 = Ewgr
“ "” r0 1 T: s
I‘ A r: :33 m9
"3 3. A particle of 1 kg mass is moving with constant velocity in the positive direction along
the sis—axis and has kinetic energy of 8 J. Another particle of 2 kg mass is moving with
constant velocity in the negative direction along the .r—axis and has kinetic energy of
4 J. What is the total momentum of this system of two particles? (a) l kgm/S 3‘: (,3 g: $2.20? = (2,) Va
(b) 2 kgm/s a“: Z © q (c) —2 kgm/s 5c 2 v: “‘2 mfg '
u‘ —1 kgm/s if: V: Li (M g, (be) r t‘ZJCZ Refer to the following description in the following two problems: A student with mass
80 kg is standing on an initially stationary cart of mass 10 kg. The instructor, who
weighs 75 kg, throws a medicine bali, whose mass is 10 kg, with velocity of 5 m/s. The
student on the cart catches the ball. There is no friction. 4. Suppose the instructor is standing rigidly planted to the ﬂoor. With what speed will
the student1 the ball, and the cart be moving after catching the ball ? ((1: mjs “6303) +6: C Io + 90 Ho) Vf
 111 S @0'5 “1/5  5o : Isaac (d) 1.0 m/s ‘ (e) 0.0 m/s VF Bus {fl/S V: 2.
7. A golf ball of mass m is hit by a golf club so that the ball leaves he tee with speed v.
The club is in contact with the ball for time T. The average force on the club on the ball during the time T is: (($771va 3:. 4, : mo ((3) (l/2)mv2T F' AT = “W 0
(d) Wig/(2T) F 2 .0221 (e) mTZ/(2U) T _ ’33 )
@191 in 8. Sand is dropped straight down onto a moving conveyor belt at the rate of 3.0 kg/s. If friction in the bearings can be ignored, the power that must be expended to keep the
belt moving at 2.0 m/s is a)l.5W b)3.0W @nw d)9.0W e)12W 9. If a wheel1 turning at a constant rate, completes 100 revolutions in 10 5, its angular
velocity is about: (a) 0.17? rad/s use ray 2” [mg : ﬂ—KZOOH ma; ZOﬂ fold/S
(b) 0.27: rad/s {as HQV MS
(c) 317T rad/s (d) 10w rad/s 207T rad/s 10. The angular velocity of a rotating wheel increases 2 revolutions per second every minute.
The angular acceleration, in rad/s2, of this wheel is: (a) 4%? A c 3% 2 ra/Wl as? 2 arm rad/S
(b) 271' ‘9 1 5 wet!
(c) 1/30 rm mils ‘ 21r/30 pi : 2;):—
(e) 471' = 32%,; 11. Three identical objects of mass m are fastened to a massless rod of length L as shown.
The rotational inertia about one end of the rod of this array is: a) mfg/4 ‘0'
b) ml?2 H)
c) 3mL2/2 ®5mL2/4 L/Z L/2
e) 3mL2 i
_... P.
I: (ME) 1‘ mate
a
= mct) + L3
: ﬁm LE 12. A disk rotates initially with angular velocity too. If a constant torque is suddenly applied
beginning at t = 0 and the disk comes to a stop at t = t1, what was the angular acceleration:
(EL) —w0t1 LL): Wu + (b) —woti ' (C) 0: me + @—wo/ti 0‘.— "’32 {e} —wfit1 4” 13. Three objects are simultaneously released from the same height and then roll down an
inclined plane without slipping. One is a solid sphere, one is a solid cylinder, and the
third is a hollow cylinder (like a hoop). All three have the same outer radius and same
total mass. Which of the following statements is correct? 2 75 W 2.. (a) All three reach the bottom at the same time. Slab Q 2
C 1nd€f @333 The sphere reaches the bottom ﬁrst and the hollow cylinder last. ® 3" YZ rm, (c) The hollow cylinder reaches the bottom ﬁrst and the solid cylinder 1ast® item? nmra (d) The hollow cylinder reaches the bottom ﬁrst and the sphere last. & V2 + iéImZ
: m .
(e) The sphere reaches the bottom ﬁrst and both cylinders arrive together later. 14. A record which has moment of inertia about its center I0 is rotating on a record player
with angular speed we 2 33 rev/min. A second record, also having moment of inertia
I0, and initially not rotating, is dropped onto the ﬁrst. The surfaces of the two records
are not frictionless. What is the ﬁnal angular speed of the two—record system? @a  I us
On) two _
(6) mo I¢NQ+Qh (InfIO.) LUf‘
(d) 2mg m I?) mo = BI?S w+ a o
(9) 4WD 21? : xx); 15. In which one of the following situations can we be certain that angular momentum is
conserved? ( when the origin has been chosen to maximize the torque
g when the linear momentum of the system is not conserved
M When the system is a rigid body Leif when a conservative force is applied to the system ’
when the net external torque on the system is zero 16. An iee skater with rotational inertia I0 is spinning with angular velocity cog. She pulls
her arms in, decreasing her rotational inertial to I0 / 5. Her angul ar velocity becomes: Ia: “00 = (15/5) LL34: (b) {do/V5 (c) cue/25 10‘“ 4 M, (d) x/gwo a, ' “C , , (e) min/5 /5 W “ 9 “)0 17. A massive disk with moment of inertia (rotational inertia rotating, but then a constant torque of 2 him is applied c
the angular velocity of the disk at the end of the 10 s? ) of 20 kgrn2 is initially not
ontinuously for 10 3. What is (a) 0.5 rad/s Ff = I d
(bl57rrad/S 2N_m= (26 game) d
( 1
rad/S 0% :I 0.: rad/52‘
(d) 5 rad/s
{8) none of these u): L00 + 0H: N: O + (Gr! rad/523C105) 2 l mats 18. A force is to be applied to a wheel. The torque can be maximized by: a) applying the force near the axle, radially outward from the axle
b) applying the force near the rim, radially outward from the axle c) applying the force near the axle, parallel to the tangent to the wheel e) applying the force at the rim, at 455 to the tangent 19. A uniform plank of mass 5 kg is hinged to a wall, as shown. The plank is 4 m long.
Approximately what upward force must be exerted on the plank at a distance 1 m from
the wall to hold the plank in a horizontal position? (Take 9 — 10 III/52). 5K?) R m)  C5k3)(;0mfs?')£2m_l :: o 8
F : (SNIODQDI‘ mo N 20. A student has suspended two masses, m1 and 1732, over a massive pulley as shown. She
is holding the mass mg in her hand, initially at rest. The mass m2 > ml. After she lets
go of mg, which of the following is true about the kinetic energy and potential
energy (U) of the objects in this system? Assume the rope does not slip over the pulley. M m1 and m2 will increase in U,
and the pulley will increase in KE. M7711, m2, and the pulley will increase
in KB, and m2 will increase in U. 1% The KE gained by m1 will equal the
potential energy lost by 7712. m1, m2, and the pulley will increase in KE, and m1 Will increase in U. )éj The KE gained by the pulley will equal
the potential energy lost by m2. ...
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This note was uploaded on 02/21/2010 for the course PHY 5423 taught by Professor Paban during the Spring '09 term at University of Texas at Austin.
 Spring '09
 PABAN

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