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**Unformatted text preview: **.- ( WEF’ULL Moe-re W172,
l’hyslcs 111 Exam 3, Spring 2016 MC’ 159)” CHE/(I (no Questions: 2 pi: ff)!‘ :1 total orzo pie) 1%
Choose the one letter that best answers the question and write it on the llne to me right. 1. A turbine blade rotates with angular velocity w(t) a 6 - 2.11! 2. What is the angular acceleration of 1. Q
the blade att: 1.20 s? A. 1.49: d/ 2
3.2.9812-82 M) : aft) : —£{_7_‘ “I:
31* mama/52 sq 1.2.») : (-LILKIJ) -;.ot( a. 0.960 red] 52 2. When the distance between two stars decreases by one ~third, the force between them 2.
A. increases to twice as much. .. increases to nine times as much C. decreases by one« i . .
D. decreases by one -haif.
E. none of the above 3. The International Space Station is orbiting the earth. On Friday, April 10, the Dragon capsule 3. A
from Space)( launched to deliver ?000 pounds of supplies and equipment. After this delivery,
the earth's pull of gravity on the ISS increased but the satellite‘s orbit was not affected. @ B. False 4. Angular momentum is conserved for a satellite in 4. E
A. elliptical orbit. B. circular orbit.
D. neither of these 5. Which rocket would - . uire more fuei? 5.
'* one going from Earth to the Mo ,1.
B. one going rom ' e Moon to Earth. C. both the same. 6. Consider a uniform solid sphere of radiusR and massM rolling without slipping. Which form 6. 0
of its kinetic energy is larger, translational or rotational? (Note that, for a solid sphere, the moment of inertia through its center is (2/5 )‘MRZJ N FED w _. E A. Both forms of energy are equal. ’ g r 13. Its rotational kinetic ener is lar-er than its translational kinetic energy. L ‘ 7. .03-
C. Its translational kinetic energy is larger than its rotational kinetic one a . J- mu’ + -’ (- M 72! _ 7__ Z— 5'
D.Youneedto ow especotesP ereoe. ‘ J. pwijvﬁi
1 MTL J' 9' MU-
7. A small mass is placed on a record turntable that is rotating at 45 rpm. The linea cceleratio 7. L the mass is
A. directed perpendicular to the line joining the mass and the center of rotation. B. inde - - dent (in magnitude) of the position of the mass on the turntable. . ; -ater the f- er t e mass is from the center. D. greater e oser the mass is to e center.
8. zero. D. centrifugal force
E. centripetal force 9. When you ride a bicycle, in what direction is the angular accleration of the back wheel?
A. backwards B. orwards C. an es between zero, “to the right," and "to e e en 3 on your ridin D. to your left
E. to your right 10. The rotational inertia of a pencil is greatest about an axis
A. about its midpoint, like a propeller. B. along its len th lead is.
( C. about its end, like a pendulum. 3
M :. €23 log 11. A torque of 12 N - m is applied to a solid, uniform disk 0 adios 0.50 m, causing the disk to
" ote that, for a solid disk, the moment A. rs kg 3. 14 kg 13. 42 kg 12. Which statement about a cell phone located on a table near the surface of the earth is correct?
A. The gravitational force on the phone is independent of the mass of the phone. B. The phone exerts a greater gravitational force on the earth than the earth exerts on the
phone. C. The earth exerts a greater gravitational force on the phone than the phone exerts on the
earth. D. The gravitational force on the phone is independent of the mass of the earth. E. The gravitational force on e p u o e eart is exactly the same as the
avitationai force on the earth due to the phone. 13. A horizontal disk rotates about a vertical axis through its center. PointP is midway between the center and the rim of the disk, and pointQ is on the rim. If the disk turns with constant angular
veloci which of the following statements about it are true? The linear acceleration o i is r- '- . . . '- . = . a e mear acce eration of ’ .
B. The linear acceleration of? is twice as great as e near acce oration o I .
C. The angular velocity of Q is twice as great as the angular velocity ofP. D. P andQ have the same linear acceleration. E. The angular velocity ofP is twice as great as the angular velocity on. 14. If you're on a Fen-is wheel at a carnival, seated 10 m from the Ferris wheel's axis that makes a
complete ru. - -' e .- .-ach minute, your linear speed is (W 'U‘: 11R B. 10 m/ min. __
c. 31.4 m/min. I
D. 100 m [min E. need more information 11. 12. 13. 14. [ m A h wiis 2. (24 points) Angular motion. Show your work and explain your reasoning.
A circular saw blade 22.6 cm in diameter starts from rest. In 3.10 s, it accelerates with constant angular
acceleration to an angular veiocity of 497000 rev/min. ("70¢“) NX‘AXﬁZﬂC‘i‘é) ($.13): 73; 01+ fee/g“ e a; (3.10 5.)
(X ; 23élg ”é?“ lo. (6 pts) Through how many radians has it turned during this timespau?
C)
l l
a 9 ., , "t 4* r EX “2"
l 3. c
r» 3» (.236 5%: :0) = 1135.2 eran§ c. {4 pts) T he website for one manufacturer lists ”Aflaximuni RPM” for saw blades. What is the
linear speed of a tooth at the edge of a saw blade ofﬂaggtgr 40.0 cm operating at its maximum RPM of 4000'? Express your answer in In/s. (Understanding this answer should help you to understand
why larger diameter saw blades have lower maximum RPM recommendations.) w s Liz-0:90 (g) 2 were “Z
Wk? ; (eggsgﬂezl : ‘33.? ”4/; F! V d. (8 pts) Four ﬂat objects (circular ring, circular disk. square disk, and square ring) have the
same mass MT and the same outer dimension (circular objects have diameters of ER and squares have
sides of QR). The small circle at the center of each ﬁgure represents the axis of rotation for these objects.
This axis of rotation passes through the center of mass and is perpendicular to the plane of the objects. Rank, from greatest to least, the moments of inertia of the objects. Greatest 1 Z) 2 14 3 C 4 5 Ileast OR, The moments of inertia of ali the objects Wili he the same.
OR, We cannot determine the ranking for moments- of inertia of the objects. we 3. (24, points) Torque and acceleration. Show your work and explain your reasoning. A block with mass m 2 5.00 kg slides down a frictionless surface inclined 35.9 degrees to the horizontal.
A string; attached to the block is wrapped around a ﬂywheel on a fixed axis at O. The ﬂywheel has a
mass 25.0 kg and moment of inertia 0.52 kg - m2 with respect to the axis of rotation. The string pulls
Without slipping on the flywheel at a perpendicular distance of 8.200 in from the axis. ”7 ‘7
"3‘2 rqééé 3t. (b) Free hotly diagram for the Wheel (a) The arrangement Figure 1: A ﬁgure with two subﬁgures a. (4 pts) The free-body diagram for the Wheel is shown in Figure (b). Expiain Why the angle
shown for the normal force is correct in this situation. +145 Vtw/ cannot Wave, 50 14mg; Must «at! “fa tare slat? x “Affection a3"; y .aolr‘res‘f‘rén , Le: r: r? 5131‘ Parallel +9 9%ij
J, ‘3 a
Ax :: Teri/75 sin few fly ‘5 7‘79 ms 35"?
b. (10 39153) What is the acceleration of the block down the ramp in m/sQ to two decimal places? I
c. (10 pts) What is the tension in the string in N to two decimal places? 75*” M5151“ Z 1;; =2 Mae :1 Wt? 59136.9’ - T #33 $1835.?” "' (1%) H WA rite, W 4. (:24 points) Exoplanets. Show your work and explain your reasoning. The X 63018? satellite has just discovered a new planet in another solar system. Follow—up measurements
with Earthmbased telescopes have discovered the planet’s two moona Laika and Albert, and you have
been tasked with a research grant to complete the following table of data. You may assume that both moons have circular orbits. {G 2: 6.67 x 10”} Iii?) ; Body ‘ Mass (kg) l Radius {111) mrbital radius (111) Orbital period (5)
Laike. | 3.60 X 102—0 (data not provided) I 210 X 10 i 3.00 x 10
Albert | 1.50 X 10 2.40 X 165 | 3.10 x 108 3 (data not provided) 3
a. (8 pts) Determine the acceleration due to gravity that you would expect on the surface of Moon Albert in 111/52. Expect a value much smaller than earth’s! 3 WW (m m x m
3mm w r“ .... g i
ﬂ (:2. 4% x {(7 ) ﬁlter? 3 0/74” “Ks-3 b. (8 pts) What is the mass of the host planet around which these two moons orbit in kg?
(Hint: Apply what you know about uniform circular motion to orbits to ﬁnd an expression for speed of
Moon Laika, then equate that speed to the geometric average speed to relate period and orbital radius.
You have derived Kepler’s Third Law for circuiar orbits?) grit“? {ﬂy-hm hi}; V ; ”MM
we‘re! pdsécl Speed : 1:1 97"AM wawlﬁ,
3
ewtrg ALWA(,2./xi£73) m M s: M» x m
f/ w 5’7": (gen 10‘"")(3x I06); 6. (8 pts) Determine the orbital period of Moon Albert in seconds. . :1 é. @ 9 K [0 2 “7...,” ,er(.?.l x 105N793
" ~me
6.6% 10"”ltéﬁ? t m”) 5
; 533 x 10 5%st wall? 5. (24 points) Sir Lancelot. Show your work and explain your reasoning. Sir Lancelct rides slowly out of the cast-2e at Camelot and onto the 12.0-m—long drawhridge that. passes
over the moat (see ﬁgure). Unbeknownst to him, his enemies have partially severed the vertical cable
holding up the front end of the bridge so that it will break under a tension of 5.80 X 103 N. The bridge
has mass 300 kg and its center of gravity is at its center. Lancelot, his lance, his armor, and his horse
together have a combined mass of 600 kg, which can all be modeled as a point particle. “Till the cable
break before Lancelot reaches the end of the drawbridge? If so, how far from the castle end of the briége
will the center of gravity of the horse plus rider be whee. the cable breaks? ...

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