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Unformatted text preview: PhySics 1 Final Exam 3/19/2008 — Freedman Your name 1. (This problem is worth 54 points)
For each question, draw a circle around the best answer. Each question is worth 6 points. (a) An object is moving along the x—axis. At a certain instant it is speeding up, and the rate at
which it is speeding up is increasing. What can you conclude about the x—acceleration ax of the object at this instant? (i) ax is positive and increasing
(ii) ax is negative and decreasing (becoming more negative)
(iii) at is negative and increasing (becoming less negative)
ax could be either positive and increasing or negative and decreasing
'(v) not enough information given to decide Direction (b) A DVD is rotating with an everincreasing speed. ofmmﬁon Compared to the point P on the disc’s surface, the point
Q on the disc’s surface has (i) the same centripetal acceleration and the same
t u ential acceleration  greater centripetal acceleration and a
greater tangential acceleration
(iii) a smaller centripetal acceleration and a
smaller tangential acceleration
(iv) a greater centripetal acceleration and the
same tangential acceleration
(v) none of the above (c) A 25.0kg crate is pulled northward at a constant speed of 20.0 m/s. One of the forces acting
on the block acts in a direction 60.0° east of north and has magnitude 15.0 N. At what rate does
this force do work on the block? @50 x102W (ii) 2.60 x 102 w
(iii) 3.00 x 102 w
(iv) 5.00 x 102 w
(v) 4.90 x 103 w 0 (continued on next page) F:K.ON 17: ((5.0N)(200M/J)C03 60.06
: (Oz—M) Physics 1 Final Exam 3/19/2008 ~— Freedman Your name 1 1. (continued) (d) The figure shows a graph of angular
velocity 002 and angular acceleration az for a particular rotating body. At which time is
the body rotating in the negative direction
with increasing angular speed? (i) time A
ime B
(iii) time C
(iv) time D
(v) time E
(vi) more than one of the above (e) A projectile is launched at a 30° angle above the horizontal. Ignore air resistance. The
projectile’s acceleration is greatest (i) at a point between the launch point and the high point of the trajectory (ii) at the high point of the trajectory
(iii) at a point between the high point of the trajectory and where it hits the ground
misleading question —— the acceleration is the same (but nonzero) at all points along e trajectory
(v) misleading question — the acceleration is zero at all points along the trajectory (f) The velocity and acceleration of an object at a certain instant are
i7 = (2.0 m/s)? + (3.0 m/s)?
a = (—0.5 m/s2)£ + (0.2 m/sz) 2
At this instant, the object is (i) speeding up and following a curved path V ‘ a " ' 5 (ii) speeding up and moving in a straight line 1 3
lowing down and following a curved path +0 . ‘9 “4 /J (iv) slowing down and moving in a straight line (v) none of these is correct : ~ 0 _ 4 “41/5 (continued on next page) KEY Physics 1 Final Exam 3/19/2008 — Freedman Your name 2. (This problem is worth 18 points) At t = 0 a BMW traveling at a constant speed in the positive xdirection drives past a stop sign
without stopping. A policewoman on a motorcycle, which is initially at rest next to the stop sign,
takes off after the BMW just as the BMW passes her. The policewoman accelerates at a constant
rate until time T, when her speed is twice as great as that of the BMW. She then slows down at a
constant rate until time 2T, at which time she is alongside the BMW and traveling at the same speed as the BMW. (a) Sketch position—time (x—t) graphs showing the motion of the BMW and the policewoman.
Draw the curves for both the BMW and the policewoman on the same set of axes, and label
which curve is which. Be as accurate as possible —— accuracy counts! x ® T<£<277 Weave Jaws/t WWO, 8mm ‘BV’ BMW :2. ‘e T Vmacemmg/BMW Physics 1 Final Exam 3/19/2008 — Freedman Your name K EV 2. (continued)
(b) Sketch velocity—time (vx—t) graphs showing the motion of the BMW and the policewoman. Draw the curves for both the BMW and the policewoman on the same set of axes, and label
which curve is which. Be as accurate as possible — accuracy counts! policewoman. Draw the curves for both the BMW and the policewoman on the same set of axes,
and label which curve is which. Be as accurate as possible — accuracy counts! T<4=<2Ti~ camshaft
® ,_ yzam zwﬁ‘wézﬁrowtr Physics 1 Final Exam 3/19/2008 — Freedman Your name 3. (This problem is worth 10 points) The potential energy of a particle moving along the xaxis is given by
U (x) = M — Bx4 In this expression A and B are positive constants. Rank the following points along the xaxis in order of the x—component of force on the particle at
that point, from most positive to most negative. If the x—component of force is the same at two 0
these points, be sure to say so. Point A: x = —, M574)“ PointB: x: _A_
4’ 48
@ PointC: x: A
ZB __
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B
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W; E X; ’fgé 1": 2g" r’“ Physics 1 Final Exam 3/19/2008 —— Freedman Your name m 4. (This problem is worth 13 points) A block moves vertically along the surface of a wall. The equations of Newton’s second law for
this block are, in component form, 2F, = Fcos60°—l’l =0
214; = Fsin60° + 0.4on— 196 N = (20 kg)(——O.50 111/32) (i) On the illustration below of the block and inclined plane, draw a freebody diagram for the
block. For each force that acts on the block, state what kind of force it is and state what exerts
that force. If any of the forces is neither perfectly horizontal nor perfectly vertical, label its angle.
(ii) On the illustration below, draw and label a vector that shows the direction in which the block
1s mov1ng. ;
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ms “5; p “F Your name Physics 1 Final Exam 3/19/2008 — Freedman 5. (This problem is worth 35 points) A block of mass M slides along a
horizontal surface. It is moving at speed
v when it collides with a spring as
shown. It comes momentarily to rest
when the spring is compressed by a . _ _
distance d. There is friction between the block and the horizontal surface; the coefficient of static friction is ,us, and the coefficient of kinetic friction is ,uk. MM (a) In the space to the right, draw a freebody
diagram showing all the forces that act on the
block at an instant between the time when it first
contacts the spring at the time when it comes
momentarily to rest. For each force that acts on
the block, state what kind of force it is and state :33. 63 eat what exerts that force. Dem +i ﬁ‘f m e— ) /
7. ea  1‘7“ Mg
:zwa .aatsu WEMk (b) Determme e force constant of the spring. Your answer should involve no quantities other
than M, ,us, uk, v, g, and d. (It may or may not involve all of these.) For full credit, show your work and draw a box around your answer. I 4/ E
led—i 4C3 121 swqgaua
CH;,sur W5 W3. 1% Physics 1 Final Exam 3/19/2008 — Freedman Your name 6. (This problem is worth 35 points) Two blocks, one of mass m1 and one of mass m2 = 2m1, are connected by a light cord that passes over a small,
frictionless pulley. The blocks are placed on frictionless
inclines; the block of mass m1 is on an incline that is 53° above the horizontal, and m2 is on an incline that is 37° above the horizontal. The blocks are then released and
allowed to slide. Possibly useful information: sin 37° = g cos 37° = % sin 53° = :1 cos 53° = % You can assume that m1, g, and the angles 37° and 53° are known quantities; your answers (*3 “T ED 91m 6 (a) In the space to the right, draw a free—body @Mﬁm %I K b7 .noliu
l diagram for the block of mass m1. For each , b
force that acts on the block, state what kind of {1'—
. . 5
force 1t IS and state what exerts that force. ma @
+\ MI W
+1 ﬁrerAJCSOHpH/u 1 ® 3 ~219reac5~ wam‘ow ﬁne wigrt;th (97 Mole (9 (b) In the space to the right, draw a free—body T +2“ 81“
EL?) diagram for the block of mass m2. For each @ 7 b7 should not include any other quantities. force that acts on the block, state what kind of ED
force it is and state what exerts that force.
+ i For ear/gt Sece— @ ‘7‘ ﬁrﬁaoétcﬂsw‘phm @ “‘23 Wm? b7 EMA
‘2 Spot/ﬂaw ﬁree i I (c) When the blocks are released from rest, which way will each block move? Explain your reasoning. m ‘_ \ (continued on next page)
@\b comm/Ci 0L i” an Physics 1 Final Exam 3/19/2008 — Freedman Your name m For full credit, show your work and draw a box around your answer. Your answer should
involve no quantities other than m1, g, and d. (It may or may not involve all of these.) 6. (continued)
3 P b (d) Calculate the speed of the blocks after each one has moved a distance d along its incline. 2
maid“”:8'“'0¢=%(2W1+“41)V 5 .S
3 2
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2 1L __ _ 4 e Suppose that there were friction between the block of mass m1 and the incline on which it ) 3‘0 I; was placed (but still no friction between the block of mass m2 = 2m1 and its incline). Find the minimum value of the coefficient of static friction that will keep the two blocks at rest when
they are released from rest, and explain why this value is a minimum. Your answer should
involve no quantities other than m1 and g. (It may or may not involve both of these.) For full credit, show your work and draw a box around your answer. so “(EMA/1283M 35L0= '53'o2m4laé 3w”?
0 "‘ g g
+( 48:“MA‘38MS3‘lT—1 gm,3+—§mlg=5w,5  ,_ 3/“ 92 +2 wplmmfﬁwa‘g 0.941 Tats Oat/u Mﬂle/MS
s s I 2 2
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#5 07; _W‘%cm53° gal/mg 3 kg Physics 1 Final Exam 3/19/2008 — Freedman Your name M l 7. (This problem is worth 35 points) A disk of mass MD, moment of inertia I, and radius R is free to turn around a frictionless axis through its
center. A light string is wrapped around the edge of the
disk, and the end of the string attached to a block of
mass mg. The block is then released. As the block falls, the string unwinds without stretching or slipping, diStanCe = ?
turning the disk. speed co, what is the speed of the block? Your answer should involve no quantities other than MD, I, R, mg, g, and a). (It may or may not involve all of
these.) For full credit, show your work and draw a box around your answer. @4 994,0 is spaealégl’lw of olx‘slr
@__,J> MAWM a} SW sped 6M ftwt ISL— (b) As the block falls, what forces do work on it? For each force, explain whether that force does
( [Zr ‘3 1 positive or negative work on the block. As the disk spins, what forces do work on it? For each force, explain whether that force does positive or negative work on the disk. W_@
+2 . — — w
W .. . Ma. >0
We lama mm «4 (ea/Q23 é 65 (a) At the instant when the disk is turning at an angular + ' : “
w MSW“ oppm’h b «WEBa, Co W<O +2 Disk: JIl—qu‘m: em eelVZc: .634 widq‘IW 4? 565517 2 w >0
(c) Based on your answers to (b), is mechanical energy conserved as the block falls? Explain q; P ‘3 why or why not.
W (continued on next page) Physics 1 Final Exam 3/19/2008 — Freedman Your name 7. (continued) lgfl? ((1) At the instant when the disk is turning at an angular speed a), what distance has the block
fallen from rest? Your answer should involve no quantities other than MD, I, R, mg, g, and a). (It a)
may or may not involve all of these.) For full credit, show your work and draw a box around { your answer. 60:5 /0 END OF THE EXAM ...
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This note was uploaded on 10/26/2009 for the course PHYS 1 taught by Professor Fridluund during the Winter '08 term at UCSB.
 Winter '08
 Fridluund
 Physics

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