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Unformatted text preview: 73 Final Exam (Barwick) Winter ’07 (Do not open until instructed) Name 6b\uihie’v\ StudentlD MC Ans (A,B ,C,D,E,F) mm: 601” Some rules before beginning: 1. Make sure that your name, ID number, and discussion info is printed on this cover. 2. You are allowed a simple calculator (see the list of allowed calculators in the syllabus) and 2
sides of 8.5 x 11 inch page of paper for notes. This test contains several blank sheets of
paper to work out the problems. You may only write in your exam. 3. You may not copy from your neighbor, nor consult or communicate with any person during
the exam. Please report any instances of academic dishonesty to myself (via email or in
person). Please be as specific as possible. 4. There are Multiple Choice and Free Response questions on this exam. No Partial credit
will be assigned for the Multiple Choice. Partial credit will be assigned for the free
response, but only if there is an absence of wrong statements, equations, etc. Write neatly. I
must be able to follow your logic to assign partial credit. Messy work will be graded harshly. 5. For the multipart problems: We will do our best not to double penalize you for mistakes in
the previous parts. Also, some parts are independent of other parts so read the problem carefully.
6. If you do not understand the questions, make sure you ask to clarify the problem. When in doubt, it never hurts to ask.
7. Please show student ‘ID or drivers license when we go around and spot check. 8. For Free Response: ll 0X ALL YOUR ANSWERS and STATE THE UNITS
 correct answer for units may be worth a '0th 0r tw 9. For Multiple Choice: Transfer all of your answers to the from or we will not grade your answers. 10. Use the blank sheets to answer the Free Response questions. Do not try to cram all your answers on
one page. Clearly indicate the part of the problem that your are answering (a, b, c, d, etc.). If we cannot ﬁgure this out easily, we may grade incorrectly.
11. For free response, symbolic answers are usually worth most of the points (unless it is trivial or given to you). If there are numbers given in the problem, then simply substituting them in for the symbols is
often satisfactory. You can leave answers in terms of irrational numbers so don’t bother with a
calculator unless you have time to spare at the end. You should include units if numbers are given though. The maximum score for this midterm is 90 pts. There are 7 MC
questions and all questions are worth 5 pts, but not all require the same
amount of time to answer. Scan the exam and do the easier problems first. There are 3 free response problems worth 55 pts.
This midterm is worth 30% of your grade for this class. You have 1 hour and 20 minutes to complete the questions. I repeat, scan the exam and do
the easier problems ﬁrst. MULTIPLE CHOICE (only one answer is correct — Make sure to transfer your answer
to each question to the front of the exam. ) All MC questions are worth 5 pts. 1.) A ball is suspended by a string that is tied to a fixed point above a wooden
block standing on end. The ball is pulled back as shown in the ﬁgure and then released. Consider two cases:
A) The ball rebounds elastically from the block B) Double sided sticky tape causes the ball to stick to the block \, Which statement is true a) The ball for case B is more likely to knock the block over No b) Both cases will produce the same impulse on the block M“? c) The temperature increase in the block is larger for case A N0 (1) It is not possible to say which case is more likely to knock over the block / _ / g/ (/ because it deends on mass of ball and length of string “#0 , .4 A
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2). Three linear sticks of different material are placed in an oven. The 1», me, T’lu,‘ S (.4117
graph shows length as a function of time in the oven. Assume that the 0:56 A. is W. _
oven induces the same time rate of change of temperature for all 3 7a” MEL ML, ,
materials. Note that slopes A and C are the same. Rank the coefficient of linear expansion, a, for each material, largest first. a) CLA>OLB>QC b) GC>QB>CLA c) OtB>ClA>GC L i C
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3.) A cylinder contains n moles of an ideal gas w1th known 7/. if the gas is mampulated a
adiabatically, what is the work, W, in terms of the given initial quantities Pi, Vi and fin 6" C) W = (PiviP VQ/(Yl) F' " La, ' I
d) w: 'Pi(Vf'\;i) W 7‘ w 1 k 6) none of the previous statements are correct [,3' ’Y 4). The figure on right shows two identical sticks with the same mass, M, and length (= 2L)
attached by a hinge. Initially one stick is hanging down at a right angle. It is then rotated so that
both sticks form a straight line. What is the distance between the center of mass of the first configuration and the straight conﬁguration?
a) L b 2L
d) L
e) none of the previous answers is correct
4 Jr ' " A “L ( far/l ) @mn + mo >1 : .3 a
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4 5) Look at the ﬁgure on I'  rig . e magnitude of the force exerted in the x direction varies ‘
function of time. It acts on a 3 kg particle. Find the impulse on the particle. a) 25k*m/ d WW k r
W WW a c) 6 kg*m/s
d) 4 kg*m}s
e) none of the previous answers is corre Whig: z (5): ti?é ‘ S 3 , Catt. I
J 6) Refer to the previous problem. If the initial velocity of the particle, Vi: 0, What is the ﬁnal
A it .4 A velocity? a) 12 m/s b) 6 m/s lc) 4 m/s l d) 4/3 m/s e) none of the previous answers is correct 7) Refer to the previous two problems. If the initial velocity of the particle was vi = —2 m/s (i.e, it was
initially traveling in the —x direction) , What is the ﬁnal velocity of the particle? b) 4 m/s (1) the ﬁnal velocity must be negative
e none of the previous answers IS correct I Problem 1: (10 pts) Jeopardy
Please write a problem whose solution is given by the equation below. (1/2)(0.006kg)(300 m/s)2 + (1/2)(0.003 kg)(600 m/s)2 =
(0.009 kg)(128 J/kgC)(327 C — 22 C)+ (0.009 kg)(2.45x104
J!kg)+(0.009 kg)(128 J/kgcxn n 327 C) Describe the system, and include the necessary information to produce this equation. For
example, does the problem assume no energy transfer? What about the forces, if any, need to be
specified? Make sure to state what is wanted. Hint: you obtained a solution similar to the one
above in the hOmework problems. @140 E5 Le Vf’rnmg
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Problem 2: (20 pts) First Law of Thermodynamics W “‘1
Look at the PV diagram. The change in internal energy along
the central path from A to C is +800]. The work done along 9 path ABC is —500 J. AVG _
AFN”: nl'S’OOJ: V a) (5 pt) Is energy removed or added as the system is manipulated along path A_liC. How
much energy is transferred by heat? Hint: Is the change in internal energy dﬁerent along ABC and directly between AC? 6 C. H B C It 8 L + W e . . mst
Cf Ag“ [gas “[(d/{Ql/t +0 5 5%,,
I 5 QWC: AEffC'Fh/MC: @3093”) ' (#5003) 1’ l“ "or ‘93 had b) (5 pt) If PA=5PC, what is the work, WCD, going from C to D? Hint: You are given the work
along ABC, which is the same as work along AB. The work along CD is simply related to the
work along AB, so once you know the work along AB, you can ﬁgure it out for CD. wk new; WM} thaw. no mam m5 sue, ﬁtf
Fen Cens‘l' Prague , W} PAV MK Angzﬂ Kb row” way11mg; é wan) 23165003)
 c) (5 pt) _ " ' a IS the energy exc nge With the surroundings, QCDA, by heat along pa
CDA? Hint: Use ﬁrst law of thermodynamics. You should recognize that WCDAzWCD, and you
found WCD in part 19. Does the ma nitnde of the change in internal energy between point A and
C depend on path? / WC“? W5 ‘ ' r s r  00J Q We I‘m (Pa/Li" Sa p
 roblem continues on next .1 CKan 1 “3003—” (WWW) : d) (5 pt) If the chan e in internal energy in going from point D to A is +500J, how much
energy must be transferred along pafﬁ C to 5? Is the transfer of energy to the system or
away from the system? Hint: Use First Law of Thermodynamics on path CD. You can determine the change of internal energy along path CD by subtracting the change along path D A ﬁ'om the beaten change between A and C (and reversing the sign since the system is now going
from point C to A ). The work along CD was found in part b. p‘DA
A];th _—. +5005 ; AErrt+AIEIHiA I {—ﬂ amen, Spam :3 ' {even/Yap
mm drag/{1cm ti {‘6’fo Wave? 149 #174; gm»; _, b5 g a); ___ C {DA
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(90 = 412% “Good”? = (*'30°T)(’°” i all 9; 99 mm am Mr 65am a heat ﬂesh/c i iﬂ‘ g Problem 3 (25 points): A tennis ball of mass 0.05 kg is held just
above a basketball of 0.5 kg. With their
centers vertically aligned, both are released
from rest at the same moment, to fall
through a distance of 1.25 m. Assume that
the basketball falls slightly faster than the tennis ball (since it is slightly denser) and 1335111
strikes the ground elastically, reverses direction, and then collides elastically with .
the tennis ball. Assume all the motion [W
occurs along the vertical axis. We wish to A ﬁnd found out why the tennis ball reaches a
greater height than compared to the case of
just dropping 'it by itself from the same h'h.
elgt Vaduz, a) (2 pt) Find the velocity of the basketball, vb, just before it strikes the ground. Him: The
velocity ofthe basketball just before it strikes the ground is vb = (ngfﬂ. Use g: 10 m/szfor the acceleration due to gravity. XL
(U) 3 (95> 0i ) 2 (Q = ‘ “ 4
Dive 68 "
b) ( pt If the collision etween e basketball and the ground is elastic, w at is the velocity
magnitude and direction (where +y is up) of the basketball ter collision. * 1 y 1‘
east; Get/151w; freng (cmseweaj ﬂaw Heap 9’“
. _, r .. _ vb
‘H’us coup. LS who Imam EA’L . .50 xiii” I m c) (6 pt) Now consider the collision between the basket all and tennis ball. The magnitude of the
velocity of the tennis ball is very close to the same value as the one you calculated for the
basketball in part (a) (because it fell the same distance). Write down the conservation of
momentum equations before and after the collision for the ycoordinate, using the notation
111b, vbi= mass and initial velocity of basketball, mp vLi = mass and initial velocity of tennis ball.
Use VM and vIf for ﬁnal velocity of basketball and tennis ball. Once you have written the
equation symbolically, then put the values in the equation that you kno . 'Tlu,._il;g{C/m3: cam is @NW 5M0”. with; 5W dLSW/ magi/u a W [amt Mam/'96 is '9‘ Mom; at: ‘ Va :— 5“
«gm: d)(5 pt) Write the conservation of energy before and after the collision between the
basketball and tennis ball. Once again, the notation, mb, vbi= mass and initial velocity of
basketball, mt, vti = mass and initial velocity of tennis ball. Use VM and vtf for final velocity of
basketball and tennis ball. Once you have written the equation symbolically, then put the values
in the equation that you know. gmbvb’fignvgfl {nVJF+§/¢gf (6M4; M; é
(0,5’)($)1+(0iosl(5)¢ r; a: 12",, + (9,0; ygf “‘87 e) (10 pt) Use equations in pans (c) and (d) to determine the final velocity of the tennis ball, vtf.
How high does it go? Based on the class demo, does your answer for the height make sense?
Hint: you may ﬁnd the quadratic equation useful: cul+bx+c=0, then x=(~b:Vb2—4ac)/2a 7/
Hm Quays/LN; (r11 Iowa‘s C. M Wdﬂ Sgt/trims 6? gym,“ 1);, Maw. amt 1g; , Many/4, apt/WW; 45,2 $0.0]? 29,25 ’63.??2’f ﬂ . {call in demo dial met
[ Bounce as Mala £0150
Cellisws he?” £14575 . ...
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 Spring '08
 Barwick
 Energy, tennis ball

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