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Unformatted text preview: 1. Calculate the net torque about point 0 for the two forces shown in the
ﬁgure. The rod and both forces are in the plane of the page. Take positive
torques to be counterclockwise. ) N p2,: :10 N F, :81“) N
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An artist constructs the perfectly—balanced mobile shown. If the artist
decides to make the star twice as massive, and not change the length of any
crossbar or the location of any object, what does she have to do with the
mass of the smiley face to keep the mobile in perfect balance? Note that
she may have to change masses of other objects to keep the entire structure
balanced. ' a) make it eight times more mas—
sive b) make it four times more mas
sive c) make it two times more mas
sive ' d) not ing e) impossible to tell Smog, 3&9 Ma‘sr3 $5126; ngw‘tl AH Masgbs
“495+ Chow» a 44ft. San/s2. QQO+DF\ 3. The ﬂywheel of an engine has ome of inertia 3.0 kgm2 about its rotation axis. What constant torque is required to bring it up to an angular speed
of 10 rad/s in 10 3, starting from rest? a) 15 N'm N L d
3 Nm 1’ x
c m . d) BUNm a" w 5 —_ Hulls?“
e) 150 Nm \O 5 2) t: 3L =3W‘ A 1.0 kg solid disc 0.5 m in radius is rolling Without slipping on a horizontal
ﬂoor at a steady 2 rad/ s. What is the total kinetic energy of the disc? a) 0.5 J K11:ka :. 14%”: 4. K macaw. m .  t . vsw
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' A hoop, s‘olid disc, and solid ball start from rest at the same height and roll
Without slipping down the left part of the track shown. The right part of
the track is frictionless. Which object goes highest up the right side? a) hoop
b soli '
d) all of them climb to the same ' ~’ “ti7"" e) it is impossible to determine ‘ , 4,52”). {‘09
Without knowing their diame— . 0170/; WW» “ﬂ «‘9 ters .  ‘ ‘ '1
"Th; objectF Wat’s 8°e5 \«xgl‘es’r \3 Thu cm W‘H” W‘— "‘05"
Jrvmuas \q+,;,m / lefxs+ «Dinhm\ \uvigHc amevw CU boHevw, 90 K H 15 +kL w H" H } 5—5 053 W 
A small (point—like blocl‘c on aﬂfrfctign‘ltgssfﬁorizfocnta‘l surfalclet has almgs§ mler‘ha / max ' of' 1 kg. It is attached to a massless cord passing through a hole in the
'sUrface, as shoWn. The block at ﬁrstYr'eVolves at a distance of 0.3 m from
I the hole with an angular speed 'of 1 rad/s. The cord is pulled from below,
shortening the radius of the circle in which the block revolves to 0.15 m. What is the. new angular speed? 13;
I m rs;
a) 1 rad/s "
b) 2 rad/s 1 rad {S
l .B
d 8 rad/s 7. 10. A circular steel wire 2 m long must stretch no more than 0.3 cm when a
tensile force of 500 N is applied to each end of the wire. What minimum
diameter is required for the wire? Young’s modulus for steel is 2x 1011 Pa. a) 7.3><10‘.~4 m. I {52‘ (bl l.§6><10,“:m) ' [1;1' ATV
) 2.05X10~ m .I ' ' C
d) 2.91x10“3 m e) .4.61x10”3m " —~— :: : ZJMQ'
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Far from the Sun (R z 00), a spacecraft is out of fuel and its kinetic energy 01 = lu‘féﬁo'} is zero. If only the gravitational force of the Sun were to act on it (neglect v other solar system objects) the spacecraft would eventually crash into the Sun. The mass of the Sun is 2x1030 kg and its radius is 7X 108 In. Find
the speed of the spacecraft when it crashes into the Sun. a) 8.0x103m19 ~§T+Ut= 0“ 0‘0 b) 1.2x104m15 ._ AWVI
c) 3.4x104mU E? In“ ‘ 2' d 7.8x104mIS ., “(mm m ..u 30 1’2 _
(e) 6.2x10f "b v ‘ 1: :2 7‘ L‘ X“) ‘ 2ND ‘ z Lam:va
. . ., . . 7105. .. . 5 Rhea, one of Saturn’s moons, has a radius of 8X105 m and an acceleration
duetto gravity of.O.3 m/sz at its. surface. At what distance above Rheas
surface is the acceleration due to gravity 0.1 m/s2? ww‘zo
r i 2. 2. '
a) 0.6x106m 81 GE 50 g” 2 f_ or y": 91 ﬁﬂfsmﬁ
1.1><10 m «*1 a p? 3‘ ” T
c) 1.4X106m
d) 1.8x106m r‘: Cir :2. LC???» 91405 = 1.3¢<¥ID‘M
e) 3.0X106m “MW = Q3“)? 2032 e~no5= aaxiosm The acceleration due to gravity at the north pole of a planet is 10 m/sz.
The planet has radius 25x106 m. The apparent weight of objects at the
planets equator is zero. What is the rotational angular frequency of the planet? r ,
a) 3.8x10‘4 rad/s W appumwﬁa 0 =5 OlajccAs “ﬁn or‘oTlr"
b 4.1x10’”4 rad/s
(c) 6.3x10”4 rad/s5 or CC, 1 d 8.7X10'” ra s a _ A
V "’ 3 e) 1.2x10~3 rad/s '/ 
Z =.L3N° 3% 11. Consider a steady laminar ﬂow of incompressible water (p = 1000 kg/m3)
in the horizontal pipe shown with changing cross—sectional area. Area 1 is
2 m2, area 2 is 0.5 m2, and the ﬂow speed at point A is 1 m/s. Find the
pressure change from point A to B (PB —— PA). a) 1.5><103 Pa
b) ~1.5><103 Pa
c) 7.5X103 Pa W 9’7“ “‘°°“‘3
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12. Consider tﬁﬂd‘following statement: The magnitude of the buoyant force is equal to the weight of the amount of ﬂuid that has the same total volume as the object. Under what circumstances is this statement true? 1r 1; a W 9va \g \E a) for an object that is partially submerged in a ﬂuid b) only for an object that ﬂoats :5 Vglv‘é) : VDESECAP c or an object completely submerged in a ﬂuid r.) Dyiec'l‘ ample‘ctla
d) or no oJec par 1a y or comp   y sumerged in a ﬂuid 5 m b wwgal e) none of the above 13. A ﬂask of water rests on a scale weighs 100 N. A small block attached to a
rod is then completely submerged in the water. The block does not touch
any part of the ﬂask, and the person holding the block will not tell you
whether the block is being pulled up (keeping it from falling further) or
pushed down (keeping it from bobbing back up). What does the scale read now?
~ move
cag¢k 1 pm (rpm/GU 'l’poske; Hr down W 59 F9 =Wwakt'lwblwlI—lT 3' wwwe'x Cage 11 ﬂbPVWOAf/W “T :0
Q9 1 meerJrl/Ubloclc. >qu 100 N
between 0 N and 100 N ) ) ) less than 0 N ) it is impossible to determine. 'T’ "Yard[ab Sup port; lalodz E
1” ,s, E; 1 W b\oL\’\
S:‘s “— WWWkw Arm/moan —T 3 wwalér
so $5 02le35 b WWakr 1(OOH 14. 15. An ice cube ﬂoats in a glass ﬁlled to the top With water. What happens
when the ice cube melts? a The water overﬂows.
c) The water level decreases.
d) To answer the question, one needs to know the area of the glass and ice volume.
e) It is impossible to determine. An evacuated bell jar is separated from the base plate by a rubber gasket, . as shown. What is'the total force bearing down on the. gasket if. the outer
radius of the bell jar R is 0.1 In, and the gaskets Width} w is much smaller
than~_R?. Neglect the weight of the glass; atmOsphericpressure is_'1>05 Pa." M a) 79x102N basket
b) 16x103N c) 2.4x103N
Ed) 3.1x103 N 7
e 4.7x103N
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 Spring '08
 Madey
 Physics

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