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Unformatted text preview: EXAM 3
Physics 122
Thursday, April 19th IMPORTANT: No scratch sheets or additional paper is allowed on this exam. This test has 4 multiplechoice questions and 4 problems to be worked out. To assist in grading  please place the answer to each question parting the box
provided. Show your calculations, methods, and approach clearly where possible. Showing
your work will increase your chances of receiving partial credit.
You have one hour to work the exam. Use g = 10.0 m/s2 for all problems. Assume all problems have three signiﬁcant
ﬁgures. Talking or looking at a neighbor’s exam will be considered academic dishonesty. Use the s ace rovided on this exam only. NAME: EEC: A WE DO NOT OPEN THIS TEST UNTIL TOLD TO DO SO! NO CALCULATORS! For Instructors Use only: Problem Score Grader MC 5
6
7
8 1. A box is moving on a tilted conveyor belt. Express its change in potential energy, as it
goes from point A to B, a distance Ah higher. a. mg(Ah) UL k; MCI/H:
b. mg(Ah) _._. — “:M‘ 3‘ ' C. mg (TA—1‘13) ALL L (1. mg (rB—rA) .1 m [3k 2. A traveler pulls a suitcase strap at an angle 360 above the horizontal. If 400 J of work are done by the strap while moving the suitcase a horizontal distance of 10 m, what is the
tension in the strap? .— a. 4000 (cos 36°) v”; UK): ‘4 (30?)
b. 40/(cos36°) F i h — \COSCQ
c. 400/(sin36°) _ W “ k0 ' j ‘ 90ch
d. 40(sin360) 3w F ___ 7., 3:“; : my?
I I ‘ lax!“ xx.) .3
MM“ 3. What is the magnitude of free fall acceleration of a ball of mass m, and radius rb on a
planet of mass Mp and radius Rp? a GM Pmb / j a
' RPZ 3 l b GM P WV C: ~:— [We {Vi/D
R 2 £3 .ﬂwwmim”
P R
GM Pmb P
c. 2
r};
d. 9.8 m/s2 4. An earth satellite needs to have its orbit changed so the new orbit will be twice as far from the center of the orbit as the original orbit. The new orbit period will be twice as
long as the original period. a. True , ,Z ‘ 3
b. False T “7H2 h 5. A uniform meter stick (mass = 2.0 kg) is free to rotate about a frictionless pivot at one
end (Icm = (1/ 12) mLZ). The rod is released from rest when it makes an angle of 30° with
respect to the vertical. sin 30° = 0.50, cos 30° = 0.87 a. What is the moment of inertia of the rod about its new axis of revolution? Is the rotation clockwise or counterclockwise? Be sure to draw a ﬁgure showing the rods
orientation and the forces acting. 2 Ipmnllel :— Icm % rind
: ' Z ‘_ 3 Z YVlL. (NF b. What is the net torque acting on the rod? Is the rotation clockwise or counterclockwise? Be sure to draw a ﬁgure showing the rods orientation and the
forces acting. leﬁll:
M“ 7.173.116 m}
Z r Kym/E : .‘LY‘ 3H130(20kﬁl(10( J
g i . , z r.
VF: Ec/QO I m c. What is the magnitude of the angular acceleration, in rad/s2, at the instant it is released?
”f;J:Q< _
ix: 1 Z 45100”) w Z ﬂ ids : 71.5 rad/S Z
1: 3‘ (masﬂlml a
(A "3 7‘3 Pad/SZ ) —u 6. A 10.0 m board sits on two saw horses as "1
shown. The board has a mass of 360 kg. Use the
conditions of static equilibrium to ﬁnd the
magnitudes of the normal forces I11 and n2. 1.0m (Min? 3 Q} n]
3: It G 4 .
,»_. _ O m1 LL: ,,_ 4» n "'
. . «   ——/ " n
“TH/"l ( 3G7O ( H) ,0 IW/S a\ 9m C 18
ﬂ 1 i ’C’ « 2000 M
V\\ ﬂ' LL) “ﬂ 2 : “9001\1 V 7_ A solid disk (1w = 1/2 Inrz) is released from rest and rolls without slipping down an
inclined plane. a. What is the rotational kinetic energy of the disk in terms of algebraic symbols? K ‘ Ler ~\/;mo
‘2 / Z L  ’Z. \/ ,/ 7
:Wmmw r
Q1, ,2
’ q HOV .L, ,1 b. Using conservation of energy determine the speed of the disk after it has rolled
5.00 m, measured along the plane (4.00 m horizontally)? Et 4 Gt;
[ : KP F?
J_ 3:. i“
mch ﬁrm/7 ‘“ 2 ‘ W2 i
mCWL' > imv’v‘ "' ‘i “N a 1 3 Z ’ M\/
i
\l 1, Y5 WWW) gaméi icor Wars? (7173 A+ B 8. A spring compressed 0.100 m pushes a ball
attached to a string. The: spring constant is k =2000
kg/s2 and the ball has a mass of 1.00 kg. a. How high does the ball swing, hmax? :11
L: L. ; 0
«I o . \ w
(,k 1‘ i M —' («(7/ + Before Aﬁer L )4 (‘53 c“ 3 mahmax' z; W2 hmay : ‘52 j ‘ m “2
2m; ZUCmLCSMW /s' 3 b. If the bail swings down from its highest point hmax to half the value of this height
(1/2 hm”), what is the magnitude of the ball’s velocity there? (a
Child—gdﬁ'ﬁVKP ’ Z
mlgiﬁmax : “é” 0‘8th "' MV ﬁhmw (L iz.\ A: Jév z a Z iiﬂkmcw : V l / VI“ : \( mom/3'2. ( LOO M
I '{n X EXAM 3
Physics 122
Thursday, April 19th IMPORTANT: N0 scratch sheets or additional paper is allowed on this exam.
this exam only. This test has 4 multiplechoice questions and 4 problems to be worked out. To assist in grading  please place the answer to each question parting the box
provided. Show your calculations, methods, and approach clearly where possible. Showing
your work will increase your chances of receiving partial credit. You have one hour to work the exam. Use g = 10.0 m/s2 for all problems. Assume all problems have three significant
ﬁgures. Talking or looking at a neighbor’s exam will be considered academic dishonesty. Use the s ace rovided on B DO NOT OPEN THIS TEST UNTIL TOLD TO DO SO! NO CALCULATORS! For Instructors Use only: Problem Score Grader MC OO\]O\UI B l. A box is moving on a tilted conveyor belt. Express its change in potential energy, as it
goes from point A to B, a distance Ah higher. a. mg (rB ~ rA) b. mg(Ah) :' y,u\:ml\£‘m*i’l'
c. mg(Ah) A“ tip L 8 8 L
d. mg(rA—rB) T. MC) Ola 2. A traveler pulls a suitcase strap at an angle 36° above the horizontal. If 400 J of work
are done by the strap while moving the suitcase a horizontal distance of 10 Hi, what is the tension in the strap? __ .
a. 40 (sin 36°) I LL) 5* F—& C (33 ® ‘
b. 4000 (cos 36°) " "7 __ T. U; _ L/GQT
c. 400/(sin 36°) 1’ 3 = 4%  , ,
d. 40 I (cos 3(0 0 ’0 m l————~/ 20m 3. What is the magnitude of free fall acceleration of a ball of mass 111., and radius rb on a
planet of mass Mp and radius Rp? a GMPmb H ,— ‘ R; be} ”' V6; b. GMT” 0/ : G: WW:
rb b 2 C GMP RF . RPZ d. 9.8 m/s2 4. An earth satellite needs to have its orbit changed so the new orbit will be twice as far from the center of the orbit as the original orbit. The new orbit period will be four times
as long as the original period.
a. True , 3
b. False T249 E
5. A uniform meter stick (mass = 2.0 kg) is free to rotate about a ﬁictionless pivot at one end (Icm = (1/12) mLZ). The rod is released from rest when it makes an angle of 60° with
respect to the horizontal. sin 600 = 0.87, cos 60° = 0.5 a. What is the moment of inertia of the rod about its new axis of revolution? ls—the the rods .
orientation'and‘the“forcesaeting.— H LmL’Z'f in (“L/Z Z
gm b. What is the net torque acting on the rod? Is the rotation clockwise or counterclockwise? Be sure to draw a ﬁgure showing the rods orientation and the
forces acting. 2 if"), F:
f", 9: ‘z r g In /
L LA.) 2/ — :— a w 1., / CU“) Z 9' c. What is the magnitude of the angular acceleration, in rad/s2, at the instant it is released?
,l’Xt‘ :_ g: k z
x. ‘ fv,‘ r”? r61 .1 Smm a p a 75 5
at A: r M g is e 75¢:szme 6. A 10.0 m board sits on two saw horses as shown. The board has a mass of 360 kg. Use
the conditions of static equilibrium to ﬁnd the
magnitudes of the normal forces In and n2. fF:O
nf +111 ‘UJ : O
27%: C:
~C e 7. A solid disk (ICM = 1/2 mrz) is released from rest and rolls without slipping down an
inclined plane. a. What is the rotational kinetic energy of the disk in terms of algebraic symbols? . ._ ' _____ ' KK"J5J,u:>Z Z V iv,
J; J. W, T;
“7
t: 2%‘mv’w
: mu b. Using conservation of energy determine the speed of the disk after it has rolled
5.00 m, measured along the plane (3.00 m horizontally)? A C¢=GP
M/ . ' .. ’
{grilﬂ gm (AL ’ Rf; 2 if :2 WWW ‘ ﬁLmV ’* Z“ “’2
\ W Z i m U
l O> ’“l m lm" “W l" “‘
_._. z a 2
Qj‘lh‘ : ‘23" ‘04"
k //_:__~____\
:Y Li (poem/51) Hm)
5
1, %0 m/ﬁ
to: o _.
is" "78 ...
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 Spring '08
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 Energy, Kinetic Energy, Mass, Moment Of Inertia

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