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Unformatted text preview: Physics 2A, Sec X00: Mechanics  Winter 2011 Instructor: B. Grinstein
Mid Term #1 INSTRUCTIONS: Use a pencil #2 to fill your scantron. Write your code number and bubble it in
under "EXAM NUMBER;" an entry in error will result in an automatic 10% deduction. Bubble in the
quiz form (see letter AD at bottom of page) in your scantron under "TEST FORM;" an error
entering the "test form" will result in automatic 20% deductions, and may lead to disqualification.
Write your name and 3digit ID at the bottom of this page and turn it in with your scantron when
you are finished working on the exam. 1) The plot below shows the position of an object as a function of time. The letters HL represent particular moments of time. At which moment in time is the speed of the object the highest? {(0 Pnsiliun A)L B)I @ D)K E)H Spud 7. m magnihde ac Vdochlgo an CM mm; or," quad
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version—page: 1 2) Bob and Biff throw identical rocks off a tall building at the same time. Bob throws his
rock straight downward. Biff throws his rock downward and outward such that the
angle between the initial velocity of the rock and the horizontal is 30 degrees. Biff throws
the rock with a speed twice that of Bob's rock. Which rock hits the ground first (assume
the ground near the building is ﬂat)? A) Bob's rock B) Biff's rock C) They hit at e same time. D) Impossible to determine f.” '30? Jvousg
w?» 3.4? i? by, we? 50b 9V0 ’gﬁtlolma » fir—v ‘‘—3"’“"\“ I (MiKCA
’ﬁt' carCOMPOde' 0? 39b; Pock"/‘ Velodth V¢c+or is —v. / ’ﬁic 1vwmponm+ n? 394'; rack'IA veloc'NY vus‘or is —n’>v, sin 3C')"=..Vo Balm races haue Hg $41M g'meonaM' as «up mum wink,
wckrs/ W 50'“! ﬂuff pro.” m 5“; loce+ion 4+ 1‘: $4.4m Me,m&g’ 50% racy. hi‘ it; around 4+ 1!. Me. Me. versionpage: 2 3) A ball is tossed vertically upward. When it reaches its highest point (before falling back
downward), A) the velocity is zero, the acceleration is zero, and the force of gravity acting on the
ball is directed downward. the velocity is zero, the acceleration is directed downward, and the force of gravity
acting on the ball is directed downward. C) the velocity is zero, the acceleration is zero, and the force of gravity acting on the
ball is zero. D) None of the above when 4k. ball reaches H—b QP¢K,'1+ i511"! new? ,and 3. +9. Va“)?
“.5 ZCIO.A 4194»ng diolacm 0.? ‘HQ loqu 4+ ﬂ}, rpmfv tooqu 0417 hue One, Greg new: cw ‘f‘v. bull' ‘Hv. acqulhffmq! ‘FOftc Qd'ma chﬂwafd. pom gau‘: #1:, yaw:
lg/ePv" Lg’amg we know 444% W) ode Come. will ram/e 4" acceleraﬁod ‘m ‘4“ 3m oart cm ‘ ’
1’ A t“ CH“ WA ward4_ versionpage: 3 4) Bill and Susan are both standing on identical skateboards (with really good ball bearings,
so you may neglect friction), initially at rest. Bill weighs three times as much as Susan. Bill
pushes horizontally on Susan's back, causing Susan to start moving away from Bill.
Immediately after Bill stops pushing, A) Susan is moving away from Bill, and Bill is stationary.
B) Susan and Bill are moving away from each other, with equal speeds. @usan and Bill are moving away from each other, and Susan's speed is three times
that of Bill. D) Susan and Bill are moving away from each other, and Susan's speed is a third that
of Bill. Nana’s 3"!4134» {ac/s 'lhwl' «allotever ﬁre; Susan Fuel: Q‘om Bill, 13;”
receives q are; {tom 5mm .c :7“! martilvlc and OppWe ‘Grcdr‘M. ‘ﬂwt'v, lu‘h people Qre 0300:": may 'Gom and. m’amd «Hau
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Aka £Ef=ma=mgiL d Sk<£g+>d€= m54.dv=MAv ( ﬁr my me. 4; eflhfs], 4a, c...“ 4w 5...“ cats 9.... gm 7; m {m maaa'vhule, as #9. 4m; 44;“, '3'.“ twelve) QM mum. .b 11"“ lmam A21“: lmaumb‘fuml / or lAQMMl= Blink”) 5) A 23 kg mass is connected to a nail on a frictionless table by a (massless) string of length
1.3 m. If the tension in the string is 51 N while the mass moves uniformly on a circle on
the table, how long does it take for the mass to make one complete revolution? A) 4.5 s B) 5.2 s C) 3.8 s D) 4.8 s N
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r is " Dfm r' “ 1911’ (5., N) = 4.35“ versionpage: 4 6) A boy throws a rock with an initial velocity of 2.15 m/ s at 30.0° above the horizontal.
How long does it take for the rock to reach the maximum height of its trajectory?
El
L, a A) 0.215 s B) 0.303 s D) 0.194 s Faint, oP MdeWYI whate V = 0 .2 «ﬂ 6
Luggage 30499 V  _
Vac59 £3 ‘ Vo’? + at 0: Voshg { ___. VgsMO __ (&.r5'm3n\«,30° _
3 "' (q‘8%a) "' 0.”:ec. versionpage: 5 \\\\\\\\ 7) Block A of mass 6 kg and block X are attached to a rope which passes over a pulley,as
indicated in the figure above. A 50 N force is applied horizontally to block A, keeping it
in contact with a rough vertical face. The coefficients of static and kinetic friction are
_u5 = 0.40 and pk = 0.30. The pulley is light and frictionless. The mass of block X is set so that block A is on the verge of slipping upward. The mass of block X is closest to:
A) 7.6 kg B) 8.5 kg C) 7.2 kg D) 6.8 kg m .14" block A i) all ‘h Verge °¢ sipping KPwafJ, 00¢ RMHJW
5}; =/(,N and M! "f‘t‘s Gic‘kml Greg, 7: direckol ’(Dwdwalds, T ' N = P
x '1' T = $3, + MA mx . .—
3 \2 mg  Aim mag
14», ‘
—r=mx3 MX=MA+ L3?
" 3 may.» " 8' O 3 N'“ all any, (MCGI $0! each Ob'aed' Decown “L spam is (5..“ bule m ezambuun, version—page: 6 8) A particle is moving clockwise in a circle of radius 1 m about the origin of an xy frame. If
it completes 3 revolutions in 211 seconds, starting at t = 0 from the positive yaxis, the
functional time dependence, with t in seconds, of the ycomponent of the velocity vector
(in m/s) is given by A)3cos(3t) B) sin(3t) D)cos(3t) E) cos(3t)
3: (1m) «95)::36] ‘ Mr“) W' flapﬂvde my kc MudOI, ﬁve. 4% is 1". rec/ft". \ Maw use. because we wé g: auxg'lm q+ {:0 we NM? 3 revIdiom '4' 4’11“ SchI.‘Th¢$"(‘p w; haw;
Oosfwéj, an M +9 c7“! 5" (41‘ an,“ at 3rwr) :> “:3 V3: ’31 : (3 "/9>(5'm f3fj) , or clw'u C 9) A particle is moving clockwise in a circle of radius 1 m about the origin of an xy frame. If
it completes 3 revolutions in 211 seconds, starting at t = 0 from the positive y—axis, the
functional time dependence, with t in seconds, of the ycomponent of the acceleration vector (in m/sz) is given by
A)  9 sin(3t) B cos(3t FO" 4“ M @9903 as above.’
D) cos!3t! g: ('0‘) 0°! [3*] E) sin(3t)
Va: 5%: = (— 37,) ‘3de] dz = %—= (_ﬁ%a>a$[3€1 version—page: 7 10) A particle is moving clockwise in a circle of radius 1 m about the origin of an xy frame. If
it completes 3 revolutions in 27: seconds, starting at t = 0 from the positive y—axis, the
functional time dependence, with t in seconds, of the x—component of the acceleration vector (in m/s2) is given by B)  cos(3t) x = (M86530 C) cos(3t) D —9 3t
Elsin(c3(:)5( ) WW? l2“‘°“ 4’ (m “*4 13*? are rm in 9mb.*8 39/4. ﬁns? use. Rem: an wmf k: o 0% int). 480, whm
{ 5 f (Sane drmellY small, "ghee dumber), Let M X +0 5: {7052+in since 4“ Md: 7, mm: clockuﬁse ’Gom (ﬁg): (0(Im3'
(«a
I’MZBEJ 42: 3€>0/ 9° We. signs an, emu, Md +,M[.~:{ detains M
X'Mo‘bu 94‘ We Parﬂclg ﬂue6'2, versionpage: 8 11) The x— and y—coordinates of a particle in motion, as functions of time t, are given by: x=4t23t+6 y=2t33t212t—8
At the instant the x—component of velocity is equal to zero, the ycomponent of the
acceleration is closest to: 2:;27‘7/32 x= WE’ 3++é
. m S
C)15m/s2 Vx= gt _ 3 = o
D)10m/s2 —"\/,.=o “Jun 6:37g g: .98 3t° we 8 v3: 669— 619— :2 a3: lat b (Wu/,3 = tat5‘ é = (—Ig) Allqulv'ha' an. in 5; Wm, r 43— /5"/,° “A... vx=ox
rt versionpage: 9 12) A projectile is ﬁred at time t = 0.05, from point 0 at the edge of a cliff, with initial velocity
components of vox = 80 m/ s and v0y = 600 m/ s. The projectile rises, then falls into the sea at point P. The time of ﬂight of the projectile is 150.0 s. vox = 80 m/s
v0 voy = 600 m/s
3’
P
(— n —>
The magnitude of the veloci at ﬁme t = 15.0 s is closest to:
A) 747m/s W C) 455m/s D)751m/s E)453m/s Vx = V0"c = 80% (no accelerqﬁoa ,4 ’Q,o(;~c+,oﬂ\ V3: V0, + q+ = 6,0075 ' 3 (’9'0m> = 453% 3 Nil: {imamﬁmsmg = lacy, A». version—page: 10 13) A projectile is fired at time t = 0.03, from point 0 at the edge of a cliff, with initial velocity
components of vox = 40 m/ s and voy = 800 m/ s. The projectile rises, then falls into the sea at point P. The time of ﬂight of the projectile is 200.0 s.
Vox = v0 voy = 800 m/s
Y P
<— D —)
The x—coordinate of the projectile when its ycomponent of velocity equals 640 m / s is
closest to: A) 560 m B) 650 m C) 690 m D) 620 m E) 590 m Firm} 9M4 #4. 41M: when Va=fa‘0"/,,M use. ‘51“ +0 94 X: ,_, V3: éL/oM/s = V014 a6 = 800% —gf _ I607
'é ‘ q 8;; = lé.3sec /___ D ‘KV.,,3(+) = (eo%>(/A3m3 = 4253'" versionpage: 11 14) A projectile is ﬁred at time t = 0.05, from point 0 at the edge of a cliff, with initial velocity
components of vox = 70 m/ s and voy = 500 m/ s. The projectile rises, then falls into the sea at point P. The time of ﬂight of the projectile is 125.0 s. Vox = m/S
Y
P
<— D —) The ycoordinate of the projectile when its xcoordinate is 3500 m is closest to: A) 430 m m First, (3nd 414 M Mr but a +° 3dr 4° ©6750!“ X’3SOOM, #94 use «W; +9 W D) +7750 m E) 430 m f 3500M =5 a’k).€ = —~—, f=506e¢ g= (vane + sq ea g: (sow/.Xgoua  502.3%») (sum)a a: 95000:"  IDDSOM = [9750”, versionpage: 12 Answer Key
Testname: MIDTERMI 1)C
2)C
3) B
4)C
5)D
6) C
7) E
8)C
9)C
10) A
11)E
12)B
13) B
14) B Name Student 3digit ID
versionpage: 13 ...
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