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Unformatted text preview: PHY 317K
February 15, 2007 Exam 1 ~— Unique number 59940 Instructions: 0 No notes, textbooks, calculators or similar aids are permitted. 0 Use the scantron answer sheet to provide the answers. Follow exactly the directions
how to mark it. Write your name, course number, unique number. Sign and date it.
Mark solutions for all problems. Mark your anSWer sheet using #2 pencil. Any errors in
ﬁlling in your scantron sheet could result in your exam being discarded. NO PARTIAL
CREDIT will be given! 0 Assume g z 10 m/s2 only where it is explicitly stated so! 0 Unless you are ready to leave at least 5 minutes before the bell rings for the end of class,
I' 'please, stay in your seats until all answer sheets are collected exactly when the bell rings (Le. you have about 70 minutes for the test). I Any questions you may have about the test have to be directed to the instructor x no
conversations and/or collaborative work are permitted. 0 Use blank sides of the exam pages for notes and calculations. A blank page is attached
at the end for scratch paper. 0 Sign the exam handout and return it with the scantron form. I PLEASE NOTE: YOU MUST TURN IN THIS COMPLETE PACKET OF
EXAM QUESTIONS AT THE END OF EXAM. SIGN IT AND RETURN
IT IN TACT. NO MISSING PAGES OR NO CREDIT ON YOUR EXAM. Answer the following questions: 1. A dart is thrown horizontally aimed toward the center point X of a target with initial
(horizontal) velocity 10 m/s. After 0.2 s it hits the target at a point directly below the
point X. How far from the point X does the dart strike the target? (Ignore any effect
of air resistance and assume 9 z 10 III/SQ.) (c 1 111 I_ Q
(d) 0.05m “rim ' E
(e) 0.01 m A:5i—3j;B=2i+3j. The symbols i and j denote the unit vectors in the positive I and y directions, respec—
tively, of the rectangular (Cartesian) coordinate system. 2. "The scalar (or “dot”) product A ‘ B is equal to: (a) 15i (b) D (c) 1 ' (d) 54 (e) none of these (EYE + (983 = w * 7 "LuL A'B '5 4*13,‘ :r 3. The magnitude of the vector A is: (a) 5 (b)14 (c)8 M1 PM? i (d) x/ﬁ (e) none of these W=ﬂ7 IO .1
In I Refer to the follow?ng statement in each of the next three problems.
The position in one dimension of an object is given as a function of time by 3(3) 2
20 m _ (2 m/s)t + (1 m/32)t2. 4. The position of the object at t 2 10 s is: X003: 20  200‘» + '00:?) = ZOZo +100 (a) 20 m
(b) 210 m
(c) 200 m (d — 00m
ﬁ‘“ '~‘= MD 5. The acceleration of the object at t = 10 s is: (a)? mm? M (b) 3 m/s2 ((3) 4 111/52
(d) —2 mfg?
...( z I
{20:30) = 5” +~=p e) 2t " (0—0+2)[ 4:“, =2 6. The velocity of the object at t = 10 s is:
(a) 0 m/s (b) 21 m/s 0—60: .0 — 2 + 20)t
@m’s ) —1m/s (e) 991n/s
’U‘lm) = I? —»2+ 2t T. A car traveling at 36 km / hour begins breaking and stops after 2 s. Assuming Monstant l
deceleration (negative acceleration) during the breaking, how far does the car travel
during breaking? Recall 1 km : 1000 m and 1 hour 2 60 min = 3600 s. (ﬁg) 5 “:11 U’ .. "()0 +a.+ see
(c) 20m 0 a no +0} (d) 80 In G kl. (8)160111 6* "ha/‘7 er I \ u
cw
.E:
K
3 8. An airplane needs to reach a ground speed of 80 m/s in order to lift off the runway. If
the runway is 1600 m long and the airplane accelerates at a constant rate (starting with
zero speed) , what is the minimum acceleration the plane can have and not drive off the end of the runway and across a New J rsey highway? (a)1rn/s2 sal’” =5 ’1. = (b) 1.5 In/s2 ! '2
x2, " 2 _, ' We x __ o 4,. + 2 6+ 'lw’f’d’)‘ 4 m/52 (“l 9'8 “1’82 x w i @l 5 755731 Refer to the following situation in the next two problems.
A cannon, which is sitting on the ground in a region where the ground is perfectly
ﬂat and horizontal, ﬁres a cannon ball into the air at an angle of 60 degrees with respect to the horizontal direction. Ignore air resistance. The initial speed of the cannon ball is
200 m/s. In your calculations take 9 = 10 III/52. (Hint: = 1.73.) 10. What is approximately the time of ﬂight of the ball (i.e., how long is the cannon ball in
the air before hitting the ground)? (a) 8'65 t: total Jam; (13% '7“ U93 "‘ (l3) 17.3 s It
4:10AM W J—MXAMB ,_ ML
((1) 12.5 s 2' Z 0  UOSI’QB a la {a 11. What is the horizontal component of the cannon hall’s velocity at the mom eat it is about to strike the ground?
of = «1" = «)0 me x
I m S 1
® 00 / 2 lgb) :5, “((1) 173rii/s
(e)871n/s : 000‘) 12. The graph below shows the position of an object over a period of time. In which portion
of the graph is the acceleration a > 0'? (a)0ét<t1 t1<£<t2
C <t<t3 3<t<i4
r
L(E))t4<t (3 13. A forward horizontal force of 5 N is used to pull a sled of mass 1 kg at a constant velocity
on a frozen pond. The coefﬁcient of kinetic friction is (take 9 = 10 111/52): (c) 0.1 (d) 1.0 (e) 0.2 A): Mar Ciaui Ue'i' {:5}anc / O /, 14. A box with a weight of 50 N rests on a horizontal surface. A person pulls horizontally
on it with a force of 10 N and it does not move. To start it moving, a second person
pulls vertically upward on the box. If the coefﬁcient of static friction is 0.4, what is the
smallest vertical force for which the box moves? .192...
[ON :01? .v
u. (a) 4N / _, n
{c 14N [3 VA” 3 a
//:f1l N
“""' (e) 35N I, 15. Two masses, m] and m2 are connected via strings as shown below. I am pulling on the
upper string to slow them down as they fall to the ground. The ﬁnal acceleration of this
system is 1 m/s2 downward toward the ground. What is the tension in the two strings?
Take ml 15 kg, m2 5 kg, 9 = 10 Iii/52. The tensi0ns T1, T2 are: (a) 0 N, 90 N
(b) 220 N, 55 T; ré'JM)“ 4, (M4 M133 ={W.+M236‘2'0~3 =” (K4? (0)) 16. A block of 1711 = 3 kg is resting on a table. The block is connected by a light, ﬂexible string over a light, frictionless pulle ass m2 = 1.5 kg that can fall freely. If the
1.5 kg mass is falling attic I ant velOCﬂQf/Bgd if there is a coefﬁcient of kinetic friction m; between m1 and the table: co pute the coefﬁcient at from the information given.
Use 9 = 10 m/s2 in any caiculatio s. 17. A block of weight 100 N sits motionless on an inclined plane, with inclination of 30°
with respect to horizontal. What is the magnitude of the normal force which the surface exerts on the block? _
(a) 50 N (b) 100 N £(c) 15 N (d) 1UU\/§ N 'ur ' I” My" d f 2 £73 = o
a ”' K N“ nioJCDSS =0 1: ,A.:«r:.;i_§..m—eﬁ~5~\ A} = M2 6059 = (WNY g) 18. A 1 N pendulum bob is held at an angle 6 from the vertical y a 2 N horizontal force F
as shown. The tension in the string supporting the pendulum bob (in Newtons) is: 19. At. some time t the velocity vector of a ball is given by V 2 5i  3j. At a later time
t’ the velocity vector is V' 2 5i + 3j. “That can be said about the force acting on the
object during the interval t to t“? . . . . . A r .. A. “
(a) The iorce acts along the posmvc :L' ELXIS. a U ..'S In WC ‘ force acts along the negative .1 axis.
e for '(2 acts alo the os'tive axis. A “‘7 4" in ._ A
(d) The force acts along the negative y axis. +0? (e) The force is zero since the length of the velocity vector does not change. 1..)
A‘U‘Jré‘; 20. A crane operator lifts a heavy wrecking ball attached to a sturdy cable. Three distinct
steps occur: (1) the ball is accelerated until it reaches the desired speed upwards. (2)
the ball is lifted at that speed upwards to the necessary height. (3) the ball is brought
to rest at the desired height. During which of these three steps is the tension in the cable the largest? (1)
~43) step (2)
. step (3)
(d) steps (1) and (3) (e) The tension in the cable is constant. 03 10 ...
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This note was uploaded on 03/20/2008 for the course PHY 317k taught by Professor Kopp during the Spring '07 term at University of Texas at Austin.
 Spring '07
 KOPP

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