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Unformatted text preview: Physics 211 NAME / NW CM; it”
Spring 2007 Recitation Time 5 Test # 1 All questions are worth 25 points. To receive full or partial credit, you must show your
work clearly. 1) If A = 5 >2 and B = 9)}, what are the magnitude and direction of (5 = A + B ? (18 points) What is the length of the shortest vector ﬁthat can be added to A that
results in a vector A + 15 that points in the same direction as C ? (7 points) W?” W? AWWWMWWWWm,Wmmwmwmw A + w; 2) A car’s (one dimensional) velocity is given by Wt) = [l .2(rn/s3 )t2 + 2.0(rn/s)]. a)
Calculate the car’s average acceleration for the time interval from t = Os to t = 25. (15
points) b) What is its instantaneous acceleration at t = 2s? (10 points) (E3) 2f ( Zia} Zf( (:2 w«WAWWWWWWWWM (mm a; I
M a, m C I} W Wit Mi: c wwmmmwwmmwxwwwmwwmmw “‘é m grist/m WWWW 3) At t = 0, a projectile is fired vertically upward from the edge of the roof of a building
25m above the ground. lts launch speed is 10 m/s. On its way down, the projectile
barely misses the edge of the building and continues downward until it hits the ground. It
thus executes essentially onedimensional motion along the y—direction. Take the
magnitude of g in this problem to be 10.0 m/sz. On a y vs. t graph, sketch the motion of
the bullet. This sketch should have three points (dots) on the y—t curve to indicate 1) the
launch point, 2) the apex of the projectile’s trajectory, and 3) the point where the
projectile hits the ground. Beside each of these points, you should indicate in the format
(y(m),t(s)) the y and t coordinates of these events. On two separate graphs, you should
also sketch ay vs. t and vy vs. .t. Use dots to indicate the same three events (launch, apex,
hit) on these graphs. You DO NOT need to calculate values of (vy,t) or (ay,t) for these dots. 31¢} 9 ya 2“; j m/Omw‘z o i / 4) A particle executes nonunifbrm circular motion of radius 2.5 m. At one point, the
particle’s speed is 22 m/s and is increasing at the rate of 30 m/sz. What is the magnitude
of the particle’s acceleration at this point? ﬂ ' m j ‘23 W WWTWWW’TWT t :2: Art] n»; with {3 w W551: QMVX
HM WWW?” “ Wait/y A» 1 MM H ““ ’ “"33 am ~ WWW W
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5:9 {23% W / :3 Physics 211 NAME / /M GA y
Spring 2005 Recitation Time
Test # 1 Questions 13 are worth 25 points each. To receive full or partial credit, you must show
your work clearly. 1) If A 2 5y, and B has a length of 4 and points in a direction 1350 counter—clockwise from the positive xaxis, what is the direction and magnitude of the vectoré , where
C=A+B? . CX A“ Bx
Q  L/ 1 if "i "' 4". ‘33 xx... :,:.4gm450 2) The motion of a particle in the x—y plane is described by the equation for the position
F(t) =12(m/53)f3)‘c+20(m/s)t}3. a) At t=0, where is the particle (5 points)? b) At
t=0, in what direction is the particle headed (10 points)? c) At t = 25, what is the
magnitude of its acceleration (10 points)? a) We) 0‘)le _/__ ‘ I I z /\ r_ A
b) VH‘} ear—m _,..¢_ Ljth x + jam/5V
 At 3 ’
_., f I A r. if j I {in}  v,‘ 1 , .
V (o) = JCT/t liq/53 y mi HM" LL I it! i I 'l I .« ﬁ 'I A
,., m \ .
C) ; «Tilt Y ..,
___._—— _......_.._———._— —,.——...__.._. W‘l "7'51 l 3) The Research Department at Corning Glass Works has determined that their Model
45F window panes can sustain a direct hit by a baseball of 20.0 m/s without breaking. A
greater speed will cause the window to break. This result pertains only to balls that hit
the window “headon,” i.e. with a velocity that is perpendicular to pane’s surface, and
was determined using a baseball cannon with a muzzle velocity of 40.0 m/s, which
launched the ball at various launch angles. To ensure that the ball velocity vector was
always perpendicular to the panes of test glass, the windows were held in a vertical
position and intercepted the balls’ trajectories at their apex. For the experiment in which
the glass barely survives, what was the launch angle of the ball (15 points)? How high above the cannon is the window in the experiment in which the window barely survives
(10 points)? The remaining ﬁve questions, 48, are multiple choice, and are worth 5 points each. If
you circle only the correct answer, full credit will be given. If you circle only one answer
and it is wrong, no credit will be given. If you circle two answers and one of them is
correct, you will be given 2.5 points. If both are wrong, you get zero points. In the case
that more than two answers are circled, no points will be awarded. 4) What is the magnitude of the centripetal acceleration a person standing on the earth’s
equator feels due to the earth’s rotation. Assume that the earth is spherical and that it has a radius of 6400 km. V2
fl
5 2 CCM‘l‘ — ~—
(A)3.4x10 (m/s). 6 R
(B‘) .4x10‘2(m/s2). V : 23w 2 En » 6.1% x L9 m _
(C)8.5 x10'3(m/s2). l 2L] .3 cc 5
2
D 8.5 10'6 111/32. _ 405 _. m
( ) X ( ) 8(6me L 1 éﬂxltﬁ (E) None of the above. 5) You throw a ballbearing straight up in the air and it lands at your feet. Neglect air
drag. The particle’s speed just after it leaves your hand (A) is the largest it will ever be while the particle is moving.
(B) is increasing.
(C) will be duplicated twice more during the particle’s free—fall. (D) Remains constant. @one of the above. 6) Newton’s Second Law tells us that F = ma, or the force, in Newtons, equals the mass
times the acceleration. What are the MKS units of Newtons? (A) (kgm)/s
(B) (m/s2>
(Q My @kgms'z) (E) None of the above 7) Two footballs are thrown from the same point on a ﬂat ﬁeld. Both are thrown at an angle of 30° above the horizontal. Ball 2 has twice the initial speed of ball 1. If ball 1 is
caught a distance D1 from the thrower, how far away from the thrower D2 will the
receiver of ball 2 be when he catches it? Neglect air resistance. (A) D2=2D1
(B) 2=4D1
(C) D2 = 8D]
(D) D1 =4D2 (E) None of the above. 8) Whatis 2~(—22)?
(A) 2
(B)
(C) 1
(D) 2 (E) Not enough information given to tell. Physics 211
Spring 2004
_Test # 1 NAME / /M Q‘Ay
Recitation Time and Instructor Questions 1 and 2 are worth 25 points each. To receive full or partial credit, you
must show your work clearly. 1) An automobile leaves the center of Lincoln (taken to be the origin of our
coordinate system), and drives around until it is at a point that is 15 miles to
the east and 24 miles to the north of the city's center. If you drew a straight
line segment from the center of Lincoln to the car at this point, what would be
the angle between that line segment and one extending from the city center
due east to someplace in Iowa? N 24 (9 = tan" 6’5 E :— (53.00]
s 2) A bomber is flying at a_ speed 600 m/s on a level flight path at an altitude of
10,000 m above level terrain. It drops a bomb. Neglecting the effects of air
resistance. what is the speed of the bomb when it hits the ground? @“W Specd =U=Iﬁl :. 3 7
2/; +25
/ / / /' ' m = Ml tr
Vi . ca/culafe, M),
——‘> Z Z
W — .:
x if), 11;), 254V
L
7f), : : 2719,331)‘
@— _ m = Questions 3 and 4 are worth 12.5 points each. To receive full or partial credit,
you must show your work clearly. 3) A particle moves in one dimension (x), with a position given by x(t) = 5m —
12(m/s)t + 2(m/s3)t3. What is the particle's average velocity (magnitude + sign)
between t = 25 and t = 53? Uav = Xz'Xr = we) —><(Zs) = /?5m —(—3m) ﬂ! éz‘ *1 55—25 35
: +éé “4/5 4) A particle rolls off the edge of a table at t = Os traveling with an initial
horizontal velocity. Neglect the effects of air resistance. Below are five graphs
for various kinematic quantities as a function of time. Draw a rough sketch of the
behavior of each variable, assuming that the horizontal and vertical speeds of the
particle are similar when the particle hits the floor. The mark on the taxis in each
case corresponds to the time at which the particle hits the floor. The origin of the
coordinate system is at the edge of the table, with positive directions being to the right and up.
or! m of comdinette 5 stem
*Yl5 ? V O—~—> 0———+x .—~——‘p~~——‘~— The remaining five questions, 5—9, are multiple choice, and are worth 5 points
each. If you circle only the correct answer, full credit will be given. If you circle
only one answer and it is wrong, no credit will be given. If you circle two answers
and one of them is correct, you will be given 2.5 points. If both are wrong, you
get zero points. In the case that more than two answers are circled, no points
will be awarded. 5) ln uniform circular motion, (A) Speed is constant and the acceleration vector is tangent to the circular
path. (B) The velocity and acceleration vectors are antiparallel to each other.
@T he magnitude of the acceleration vector is fixed.
(D)The particle‘s speed is proportional to the square of the velocity. (E) None of the above. 6) A particle is thrown straight up in the air. When it reaches its maximum height (A) Its acceleration is zero. (B) lts velocity is a maximum. (C) It feels the maximum force of air drag. @ts speed will begin to increase. (E) lts centripetal acceleration is a maximum.
7) Newton’s Second Law tells us that F = ma, or the force, in Newtons, equals
the mass times the acceleration. What are the MKS units of Newtons? (A) (kg'm)/S (B) (m/SZ) (C) (Slkg) 8) Two cars are traveling in xy Cartesian space. The blue car has an x—
component of velocity of +50 mph and no y—component. The red car has an x
component of 40 mph and a ycomponent of 30 mph. Which of the following is
true? (A) Both cars have the same velocity. (B) The red car has a higher speed than the blue car. (C) The blue car has a higher speed than the red car. Both cars have the same speed. (E) None of the above. 9) A particle travels in xy Cartesian space with everincreasing speed anti
clockwise on a circle of radius R centered at the origin. Just at the point when
the particle is on the positive xaxis
(A) its acceleration vector points into the first quadrant.
s acceleration vector points into the second quadrant.
(C) its acceleration vector points into the third quadrant. (D) its acceleration vector points into the fourth quadrant. (E) Not enough information given to tell. __/
Physics 211 Name [ g Spring 1998 Section / 5 0
Test #1 T.A. Each question is worth 20 points. 1) A dragster has a maximum speed of 300 miles per hour. What is this speed in meters / second? @
(3‘00 thXégaayl mam) : {/33 "lbac W Ix W 5/37? Cam 2) During a race, a bicyclist accelerates with a constant 5 m / 52 along a straight
racecourse. An observer standing at the track edge observes her to have a
speed of 15 m/s as she goes by. What speed does a second observer, 25 In
further down the track, observe her to have as she passes him? (73 V{Z‘V£1 : ,2an
1 @GD _
\,/](z z )5 +2525  Z7’75 3
O E=2L§Wsl ' GD WW mar(“[554 a Wm T7 z _ q f, ,5. (“bananav 0% AM”
Mr IT W
“ﬂew rmmﬁ <:~ mm mug; “a 3) A particle has the following position vector in a righthanded Cartesian
coordinate system: f(t) = (Sm/s).ti+(7m/s)ti. At t = 0, what is the direction of the particle's velocity vector? (Give your
answer in degrees counterclockwise fromAzlr.) GD @[email protected] V=§f=5%i+7m/SJ @
5° &= ten” {15% ‘55“"(5‘54 @ 4) A = 4} + 512 , and B = 3; — 1012 What is $5 angle between these two vectors? GD
AIB = ABCosg ‘ AXBX‘lAyB/‘FAEEZ 5) A mortar sits on a level plain and ﬁres a projectile at an angle of 30" above
the horizontal. If the range of this projectile is 1 km, what is the maximum height above the ground it reaches? Neglect air resistance. Assume points along the upward vertical direction. Make a reasonable sketch of the
graphs: y vs. t, Vy vs. t, and ay vs. t on the axes provided. Your graphs do not need to have any numbers or labeled points on them. l
cWOO /z_ ﬂ,— 0. 966 Quiz #2 Name
Physics 211
Spring 1995 N) Multiple choice: 1) Acceleration is
i) positive
ii) negative
iii)zero
iv)not enough information given to tell. 2) Velocity is
i) positive
ii) negative
iii) zero
iv) not enough information given to tell. 3) X0 is
1) positive
ii) negative
iii) zero
iv) not enough information given to tell. xm va) Quiz #2 Name
Physics 211 Spring 1995 Given the graph shown below of x(t), sketch v(t). I
A Physics 211 Name 1 [mg 2H X x Section 150
Spring 1995 o g = 10.0 m/s2
Test #1 0 Do not reduce transcendental numbers. D ~ 1) Using the rough estimates of the radii of the sun and earth given in Chapter 1,
what is the ratio of the surface area of the sun to that of the earth? (10 pts.) 0’:z::hlf rSun m m A} A San _ __ [I j [flu _ [if of
I?" ’ "' " t l r ream‘k ~ ’0 7m A amt 471' V62 4 n ([email protected] D .— 2) The price of land in downtown Lincoln is one hundred million dollars per square
kilometer. What is the price per square mile? (10 pts.) @ g »[email protected] I ’ x ['6 I‘GL =(94'2.GX/O®/MILL\I M x
z . V W
km L m Q Q \®/ [C can 'v’c”: V." wt _L§__ AT: far
,26 w (23 256
D —— 3) A vector points at 30° above the ﬁ axis and has length 16111. What is the dot product of this vector and the unit vector 9? (10 pts.)
0 .
= SM 30 v [6m =é§¥h\
I 9 A? = '47
«:5 l A @ @0
WW x W
(arrrid ®
chem" C — 4) 52x159 =1?" (10 pts.) A C " 5) The driver of a car traveling at 30 m/s sees a brick wall directly in front of her 250
m away. If she immediately applies the brakes and continues in a straight line,
what must be the value of the car’s deceleration to prevent a crash? Assume
constant deceleration, and that the driver has a reaction time of zero seconds. (15 ts.) z
p 7.1,} = nglean’XojéD
L:le averted {If X“Xo 2' 2‘50 "4/ when U1} : 0 Crash '
‘/ C32 299
500 = [9 2 z x 7
was; 2) <23 @
x dé cm
U— IS. =
y @dt vy—Lr @ €51U=qogl AT.“ 7) A particle travels with constant speed on a circular path of radius 2 m. If it makes it
around the circle in 4 s, what is the magnitude of the particle’s centripetal acceleration? (15 pts.)
U Z / ® a . 2 __
cewinpeial R T \ 8) A mortar perches 50 m above a level plain at the edge of a cliff. It fires at an elevation (an) of 45°. The maximum height reached by the projectile is 200 m
above the plane. What is R, the range of the projectile? (15 pts.) 723.56 may: i? @[email protected] ,f‘ ._. 23
@\ '1—
: I50 = 7)?)
1/0
End" +0 scale: .1 U22 £6000 Z
loaf} = f M _ J— ) L t
y 3V? OX Zigzcoszwo X r: L _____ _ _ __ _..I..—— 2'
X—Eooox Q godR 60C)E R1 6‘OOK * quoo ‘ O J R = [509: llamas +/,_a_x,os]/2,
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= l65r/OZMZI'O' 4. ,
592’ E700 3; V w 700 u/
A Physics 211 Name //M gay Section 150 0 g = 10 m/s2 Spring 1995 0 Do not reduce transcendental numbers. in
II UL
O 4. O + N 0 ll U‘]
B 2) How many liters of water could this room hold? (10 pts.) fowumaié Gathh/J def MUM : l 0,141 X lO/M " lOm [email protected]
" IE: Io'[email protected] a? [/Ogﬁl
2&2“ng 3) What is the acceleration of gravity in units of meters/hourz? (10 pts.) 33c 6) (3)
£9.“
zlé / 05
' lzqg 4) What is the angle between 3' and (—3)“:— 49)? (10 pts.) No” ?7" = /43° _...—— AB = —4 <3)
37°? = SCOSB' Q ? cos 9" = "O Y
(9‘ = Cos"(o,?) q; 5) A particle executes uniform circular motion in the xy plane on a 5m radius circle centered at the origin. It takes the particle 1: seconds to make it around the circle once.
What is the particle’s acceleration vector when it crosses the +y axis? (15 pts.) @[email protected] 6) A gunner in a helicopter is 80 m above the ocean and fires a bullet straight down, with a muzzle velocity of 30 m/s. Neglecting air resistance, what is the projectile’s
velocity when it hits the water? (15 pts.) SW m @ L U = U‘Z‘Z { “" o)
f @cq [email protected]@
' "20(“8’Oi
= ‘iOOHGoo = 2500 u
w
0 7) Consider a particle at the origin at t = 0, with V,"o = 0; V” = 5 m/s. If the
acceleration vector of the particle is 5(t) = SCI/2 )i, where is it at t = 15? (15 pts.)
5 @ W60
@ i Hts) = 2.51,»; + 5m;
@ W 8) If a gun can shoot a projectile a distance of 1 mile on a planet with no air but with
the earth's gravitational pull, how far can it shoot the same projectile on an airless
planet with one fifth as much gravity? (15 pts.) 0 Q Le mum X
Cnci 11)Consider a particle executing circular motion. The centripetal force acting on
it (5 points): A) ( ) drops to zero if the particle begins to accelerate tangentially.
B) ( ) is proportional to the particle's tangential acceleration. C) 90 doesn't depend on the particle's tangential acceleration. D) ( ) is proportional to the cube of the particle's tangential velocity. ...
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