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Unformatted text preview: 5 Dynamics 1:
Motion Along a Line 5.1 Equilibrium 1. The vectors below Show ﬁve forces that can be applied individually or in combinations to an
object. Which forces or combinations of forces will cause the object to be in equilibrium? «I— .3.)
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3* r9 0" Feel:6 l' "115 '2. Are the objects described here in static equilibrium, dynamic equilibrium, or not in equilibrium
at all? Answer Static, Dynamic, or Not. a. A girder is iif ted at constant speed by a crane. Mm
b. A girder is lowered into place by a crane. It is slowing down. L
c. You’re straining to hold a 200 pound barbell over your head. L
d. A jet plane has reached iLs cruising speed and altitude. Am.
e. A rock is falling into the Grand Canyon. L
If. A box in the back of a truck doesn’t slide as the truck stops. m..__N°r— 51 52 CHAPTER 5 ‘ Dynamim I:MuionAlongaLinc 3. The free—body diagrams show a force or forces acting on an object. Draw and label one more
force ( one that is appropriate to the situation) that will cause the object to be in equilibrium. ." ‘1 l ‘5 $1 4. The freelmdy diagrams show a force or forces acting on an object. Draw and label one more
force (one that is appropriate to the situation} that will cause the object to be in equilibrium. 5. Write two or three sentences explaining why you agree or disagree with the statement: “Forces cause an object to move.” .
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c"""""‘.}' l‘“ vii9'53.“ Hat“l" IMO“’6'". 6. If you know all of the forces acting on a moving objecL can you tell in which direction the
object is moving? If the answer is Yes, explain how. If the answer is No, give an example. l‘lO. I}: You illnow a“ ghlﬁm 'HIA You “"0 'Hme d{n¢.di0n or? ﬂu— nccduﬂien , m‘l‘ 1'an “WM. For etc“Kr“, ansr a. “ct“ {grw guruPug If? SPJ
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0* mush—A— 99452. Dynamics It Motion Along a Line . {f HA PTE R 5 53 5.2 Using Newton's Second Law 7. a. An elevator travels upward at a constant speed. The elevator hangs by a single cable.
Friction and air resistance are negligible. [s the tension in the cable greater than, less than,
or equal to the weight ot‘ihe elevator? Explain. Your explanation should include both a free
body diagram and reference to appropriate physical principles. Bee who. 'HnL {ieh'h’f‘ u Ao‘i‘ Mutteradios), fl“, “‘1' For1:
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if: h. The elevator travels downward and is slowing down. Is the tension in the cable greater than,
less than. or equal to the weight of the elevator? Explain. BECam'l'lvV ﬁlQW‘i‘Dr C5 skewing JONInt!“ acc£l£QETvL
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Exercises 8—9: The ﬁgures show free—body diagrams for an object of mass m. Write the x— and
vComponents ol‘ Newton’s second law. Write your equations in terms of the. magnitudes of the threes F1, F 3. . . . and any angies deﬁned in the diagram. One equation is shown to i]lustrate the
procedure. .‘I
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mm. : Fl — F3 mo‘. : Ft ﬁtne' +173 Stu95— Fa. 54 CHAPTER 5  Dynamiw 1: Motion AlongaLine 9. max 2 F3 cos 6‘3 — F4 may 2 Fl *FS 5'“ 9'3 ‘ F2. Exercises 1012: Two or more forces, shown on a freebody diagram, are exerted on a 2 kg
object. The units of the grid are newtons. For each: ° Draw a vector arrow on the grid, starting at the origin, to Show the net force 126:.  In the space to the right, determine the numerical values of the components ax and 0).. 11. _ osﬂ ‘ gr"  ﬂt N a ‘ " a 2"th l l ) “5 at‘ “L (3“ 4:0 " 0'5 ’5‘
233 12. a = ’L (aﬂlﬁ‘g’h: [S 55" “y: J Llﬂ+2M‘3N): O 95.1.
1“: DynamicsI:MotionAlongaLim  CHAPTER 5 55 Exercises 13—15: Three forces Fl, {32, and F} cause a 1 kg object to accelerate with the
acceleration given. Two of the forces are shown on the freebody diagrams below, but the third is
missing. For each. draw and label on the grid the missing third force vector. 13. a = Zimfsz 14. ii = —3jml's2 UN) 15. The object moves with
constant velocity. . . : ’ ”PM
.31: 5 16. Three arrows are shot horizontally. They have left the bow and are traveling parallel to the
ground. Air resistance is negligible. Rank in order, from largest to smallest, the magnitudes of
the horizontal forces F1. F3. and F3 acting on the arrows Some may be equal. Give your
answerin theform A>B =C>D. '31—; 10 mfs W 9 m 9 m
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Only Por'u. on ﬁv mods U414. cit0H“ Hull. 0'? «arrJ31 . 56 CHAPTER 5  DynmnicsltMocionAlongaIAne Dynamics l: Motion Alongaline  CHAPTER 5 57 5.3 Mass and Weight 1?. Decide whether each of the following is True or False. Give a reason!
a. The mass of an object depends on its location. Riki M065» as Jllungﬂmm‘l‘hl ”ﬁrst47 ‘Hwt‘l Ska'5 k0“,
an channel" (45 Panels 1'0 a. 99:16. 0. Mass and weight describe the same thing in different units. False  Noah? 15 0; F99“; mass am, 50 Nina Juanitagall,
&t$¢¢"ﬂ‘t. “can“? Mc; “'Jﬁ‘3 4‘ M 5"“. .P ailu"; .17. '18. An astronaut takes his bathroom scales to the moon and then stands on them. Is the reading of the scales his true weight? Explain.  ~ ‘
The Scalﬁs tarIll m9. I'MS Mtgf? 9" “‘ MGO" . TLCf a.” sact null. 4d» m45k+ +krt he to,“ M £...+\ . 19. Four balls are thrown straight up. They have the same size. but different mass. Air resistance is
negligible. Rank in order, from largest to smallest, the magnitude of the net force acting on
each ball. Some may be equal. Give your answer in the form A > B 2 C > D. 2033 Order: 4 > 3:. 27 l
Explanation: 1. ' aim \
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lawc1. 15 i“ SW’“ “'5 9” 58 (HA PTE R 5 . lb’namics 1: Motion Along a Line 20. The terms “vertical" and “horizontal” are frequently used in physics. Give operariona!
deﬁnitions for these two terms. An operational deﬁnition deﬁnes a term by how it is measured or
determined. Your deﬁnition should apply equally well in a laboratory or on a steep mountainside. Vet«ml chunk degmull by ‘l'La. UM Os Plumb Ionb Make; Mun“inc; clown elmI. h 04mm”. cﬂtﬁhGol '97 ”Finl. 5%,“ch 9+ 0‘ Ii'quig! ' lac.
H'Dr'l‘ﬂnhk Cm babble lcwl. 4P1” J3“... ha. “Lag: o‘l'ui'l': ﬁlmmaker or by Ming, 9. 2 l. Suppose you have a jetpowered ﬂying platform that can move straight up and
down. For each of the following cases, is your apparent weight equal to, greater
than, or less than your true weight? Explain. ID : “Rm1 Musk" a. You are ascending and speeding up. w 1. h“; ”ﬂaun
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0.3430 “we Dynamics 1: Motion Along a Line  C HA PTER 5 59 22. Suppose you attempt to pour out 100 g of salt, using a pan balance for measurement, while in an elevator that is accelerating upward. Will the quantity of salt be too much, too little, or the
correct amount? Explain. You. will 91"“ ?our Hm. correct amoun’l‘. (Unaask ‘HNL Augean«*
minkﬁ' is (“CdCaste! Tu 'Ha. dewdo! (“3th medial Lenoh: pour3 i190 li‘i‘i‘ie. (in m 9Pf'iv13 Static)! Han. Pawn, biolance. campercs “0.
mass 0? #14. SnH' ﬁnwr—«eﬁ W'i‘l‘k (“LL MAI: 0&5. laneJim 1003 95”. (Bark wastes areaHes at 57 (”LL accele adieu. JudLa. sane.517 23. A box with a 75 kg passenger inside is launched straight up into the air by a giant rubber band.
After the box has left the rubber band but is still moving upward: a. What is the passenger's true weight? 0.); W3 = 19.3 (ms—“go = 135?! b. What is the passengers apparent weight? .2 e {0 0*?!)
. = (J
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: l“ "3. : L) 1" I) F O  24. An astronaut orbiting the earth is handed two balls that are identical in outward appearance. However, one is hollow while the other is ﬁlled with lead. How might the astronaut determine
which is which? Cutting them open is not allowed. 11.ng MQHJL +0 act2.1m“: OWNObj”! t's ffofor’i'law~l shoalJ" Mods. (15.: max). ﬂus’m Qfﬁ'oﬂoun‘i “mob, M,“
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afoc.‘ {liarcg. (TLL $.ch retina0A ha a telm‘i'L deluge...“ is its; ch44. +D'i‘i3 [0‘3" ”as: 510 CHAPTERS . Dynamicsl:MaionAlongaLine '25. Suppose you stand on a spring scale in six identicai elevators Each elevator moves as; shown
below. Let the reading of the scaie in elevamr n be S”. Rank in order, from largest to smallest, the
six scaie readings St to S6. Some may be equal. Give your answer in the form A > B = C > D :j: Steady
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um . PC“ I Dynamics 1: Motion Alongaline  CHAPTER 5 511 5.4 Friction 26. A block pushed along the ﬂoor with velocity in slides a distance d after the pushing force is
removed. a. if the mass of the block is doubled but the initial velocity is not changed, what is the
distance the block slides before stopping? Explain. Whlmkuﬂl wot... Hat sanctum“. A. TIM—M1130
4291'“. ’15 Profornbml "1'0 Ha. mass, but block's response.
i" M‘hgoru is also ?Fofor'hhvs~l h it; mat”; So 1]... acceleration 1.5 H» Swat. b. If the initial velocity of the block is doubled to 217‘, but the mass is not changed, what is the
distance the block slides before stopping? Explain. ”TL... himJo mu shat “Atom“, q, ‘4 d. “gem“; ﬂame
“i5 MWaﬂcgﬂ‘l will +£11 fury)... die11"“ +5 lose. fut“). {L1 uekaeﬁu’, 3mm ”ﬂu. avercage \KloethY is 0450 doubled)? 2?. Suppose you press a book against the wall with your hand. The book is not moving.
a. Identify the forces on the book and draw a free~body diagram. *7 i Thl’m“, “the: 0
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W El = $5 " "° " b. Now suppose you decrease your push, but not enough for the book to slip. What happens to
each of the following forces? Do they increase in magnitude, decrease, or not change? ﬁmh Atcnases
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J: Same. cl ecreasas ﬁlm 512 CHAPTER 5  Dynamics [: Motion Along aLine 28. Consider a box in the back ot'a pickup truck. a. If the truck accelerates slowly, the box moves with the truck without slipping. What force or
forces act on the box to accelerate it? In what direction do those forces point? +r “(J‘— c
h. Draw a freebody diagram of the box.
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ﬂ 0. What happens to the box if the truck accelerates too rapidly? Explain why this happens.
basing your explanation on physical models and the principles described in this chapter. $1“; +ke. genderMoo 15 W1 lac31 ‘hum'd' Mr requn.
O~ Ii'uoze. «M‘Hhe. box. («ﬂan sawe oﬂiMc‘hbn 'i'imti' QKC£¢4Q$ +1“— vuagimm Force "Ha1’ Cam in. proudnot b7 rh'hc. ‘P'rt.c.l'lbn’ :5 : M5, ha: I“ Hi“; Case, +1.1:— ‘vlo all. will MW“
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Owl Q‘NW‘ unJAFKerﬂvx'alr Uta hackuorols ) mixwk mall acctlmm “in; 7+ +0 “Hg".‘lu Sll‘Je Dynamics l:MotionAlongaLine ‘ CHAPTER 5 513 5.5 Drag 29. Three objects move through the air as shown. Rank in order, from largest to smallest, the three
drag forces DI, D2, and D3. Some may be equal. Give your answer in the form A > B = C > D. Order: D171); : '93 . 1 , '1
Explanation: “5M3 PD: 11!. R U1, +Len Pr; : 0'06"}! A1. = 0,0491 , fig—0.0"!“ gm— ‘4’“: Ufggelcg—l: we vg‘eterg So v,:.s‘v~,’o.:.%nt
b3 =I$6N' 30. Five balls move through the air as shown. All ﬁve have the same size and shape. Rank in
order, from largest to smallest, the size of their accelerations al to as. Some may be equal.
Give your answer in the form A > B = C > D. 503 ”mg 50g 100g lvlﬂmﬂs
Just released Just released v=20 THIS i v = —20 11118 50 g
1!:0 v=0 Order: as) (31.:(,‘;‘1_>(1,f 7Q; .
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loan ct is %WAW Hum was? lead a seam “an. expm 1‘an Souhul olrota foru. «~52 balk ‘4 EXPO—ruewm 9!. careHf ca mdﬁi‘llmi £01112. 31. A 1 kg wood ball and a 10 kg lead ball have identical shapes and sizes. They are dropped
simultaneously from a tall tower. a. To begin, assume that air resistance is negligible. As the balls fall, are the forces on them
equal in magnitude or different? If different, which has the larger force? Explain. 514 CHAPTER 5  Dynamics 1: Motion Along a Line b. Are their accelerations equal or different? If different, which has the larger acceleration? E1321 Explain. (“mumsN «LL {torus all ﬁrthJ5“? is 10 *{MQ’ larﬁnu— on‘ﬁ‘LI. [014$
[Causal kinll, H‘s rcsns'llnuu d‘b acﬁelm—ﬁ‘“ Clnefh“3 {S also to 41m ﬁMaW.C—MQ:Mat or" cur*3 'FDr LaoHQ c. Which ball hits the ground ﬁrst? Or do they hit simultaneously? Explain. 3mm . ' AM he: bf"
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wi‘Hm ‘l’Ln. {AM—0. nccelm'hbon _'1_LQJ‘£+ur0_’ ‘HJLYIQMQ aﬁl' VH—LS'artc'hH, d. If air resistance is present, each ball will experience the same drag force because both have
the same shape. Draw freebody diagrams for the two balls as they fall in the presence of air
Igsistance. Make sure that your vectors all have the correct relative lengths. [a ,3 b ‘l (ELOHS ‘ 3m par"T a. below) .3 to e. When air resistance is included, are the accelerations of the balls equal or different?
If not, which has the larger acceleration? Explain, using your freebody diagrams and Newton’slaws. mum; but has or arcder «cedarKhan. (BCCmm Hun. 6.133 force. is TnMaQEA? a? H... wassf'i‘iwlll ‘ ‘ an ap
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m \{atolx ball. My.“ mum,“ Scams! L...) Ian. “J  M .. aha}? : 3,%. Tiny”. MimraJIl‘ MasraQ'*LLLea& ball v1 m “balm 0'? *‘Laccce (”I—ltkr lama (.1
lLataes ”n: A Smaller c ‘0 (902893: ‘:rr'¢SlSW). f. Which ball now hits the ground ﬁrst? Or do they hit simultaneously? Explain. ml‘CADS ‘9...“ at“ [113+ 1H,.“ am“..&_%r3+ began6'8 "‘4: has 0..
(a peaRf— Maﬁathem. accelem‘h'bu _ 5.6 More Examples of the Second Law No exercises. ...
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 Fall '08
 Graff
 Physics

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