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Unformatted text preview: PHY 3HK
as March, seer Name:.................... Exam 2 — Unique number 5944!} Instructions: : Take alternate seats if possible.
I No notes, textbooks, calculators or similar aids are permitted.  Use the scantron answer sheet to provide the answers. Follow»:r exactly the directions how
to mark it. 1White your name, course number1 unique number. Sign and date it. Mark
solutions for all problems. Mark your answer sheet using #2 pencil. ND PARTIAL
CREDIT will be given! I Assume g = ID mg's2 onlyr 1where it is explicitly stated so! I Unless you are ready to leave at least 15 minutes before the end of class please, stay in
your seats until all answer sheets are collected. I Any questions you may hate about the test have to be directed to the instructor — no
conversations andfot collaborative work are permitted. I The last 2 pages contain some equations and other information that may be useful on
this exam. You may not ask questions about this sheet, however. I Use blank sides of the exam pages for notes and calculations. I Sign the exam handout and return it with the scantron form. Answer the following questions: 1. A pendulum consists of s 5 kg mess suspended from the ceiling hy s string of length
1.6 n1. If the pendulum is released from a position where the string makes an angle of
ED degrees with respect to the vertical, what will he the speed of the mass at the bottom of the pendulum’s swing? Ignore sir resistance and take 9 = 10 mfsg. {a} 1D nifs 1N : i/ul
h Brnlg’s I
mfs g V 1. lﬁ Smfs 1 '— H — JF [e} Enifs {(lfmsb ah :1) ‘QEEB ff.
:: Ll W5 2. A It! kg mess is relessed from rest 20!] n1 shove the ground. 1When it has fallen 5G in {LE1
when it is 15H m shove the ground)T its kinetic energy is about (ignore sir resistance .. g = ll] mjsij:
[it] .1 {h} 1D.ﬂﬂﬂ J {c} 2]:Dﬂﬂ .l [d] 200' .l (e) 10 .l my" :‘Jiwui m MezasIﬁ=fas~ 3. An ides] spring is used to ﬁre s 50' g block horizontally seross s frictionless tshle top.
The spring has s spring constant l: = ED me and is initially compressed by 7 cm. The
speed of the block as it leaves the spring is: {e} To cmfs 7! .2 i/
{h} TE:me ’ {ilk}: 3' mu:
mg’s /
ﬁg: “"135 / u e 5 2r
[e] 1.4 cmfs w it. A particle of 1 kg mass is moving with constant velocity in the positive direction along
the :aaxis and has kinetic energy of E .1. Another particle of 2 kg mass is moving with
constant velocity in the negative direction along the r—axis and has kinetic energy of 4 l. 1What is the total momentum of this system of two particles? to Ikemisﬁt J W'l : 14E
{1)} 2 kgmy’s it {c} —2 kgmfs i
{d} —i kgmfs it 9 ZBID 5. A physicasavvy hockey player wishes to shoot a goal from 12.5 In out. Knowing that
the hockey pack she ﬁres at the goal will experience a frictional force with coefﬁcient
of kinetic friction in, = [LlT and recalling her PHYEITK class, she knows that she must
give the hockey puck a hard shot to have it reach the goal without slowing to a stop
ﬁrst. What initial speed on must she give the puck in order to have it reach the goal? You may assume 9 =1ﬂ nig'si. {a} 25 mfs [b] 12.5 mfs fs {d} 2.5 mils
the mass of the hockey puc is known. ﬁddle # A \l 1:. 7“ y 2613.! )(I13a'233'3 E. A mass in at the end of a l1ght ring is held such that the string is horizontal {the left end of the string in the picture is held by a ﬁxed support}. The string has length r.
The mass is then released from rest. and it swings in the circular arc indicated. What
is the tension force of the string when the object is at the lowest point of its swing?
Hint: Use conservation of energy. Keep in mind what is it that provides the centripetal acceleration. Do a free hody diagram of the mass! tel ms rig—34oz: re ll 2 II {b} 2m. I I
9 \J n " r  s T {e} 5m {e} cannot say unless \I _ ‘f it’ssﬁ/M T. A very massive object travelling at 1B in '3' s strikes a very light object~ initiallyr at rest.
The light object moves off in the direction of travel of the hear}r object. If the collision is elastic, then the speed of the lighter object is: W. “1. {a} me I ‘—=s~ s
[h] It} infs 2
{c} 15 rolls “1 1 ( l _
"L U +" C} .Iyl '
ﬁﬁmla 1)“? “little '
e eﬂmfs z”
.4; i "
a 2%: I“
= '20 M: 8. Sand is dropped straight down onto a moving oomreyor belt at the rate of 3.1:) kgfs. If
friction in the bearings can be ignored: the power that must be expended to keep the belt moving at 2.0 infs is a] Lew meow ﬂu! s}e.sw e112“?
2
1% zit—aux“ t geoizeLq‘m) 9. The angular velocity of a spinning wheel points ought this page. If the angular accelerv
ation vector points into the page. then .
a. {a} the wheel is spinning clockwise but slowing down. the wheel is spinning clockwise but speeding up.
he wheel is spinning counterclockwise but slowing down.
(d) the wheel is spinning counterclockwise hut speeding up. is) none of these. II). If a wheel, turning at a, constant rate, completes lﬂﬂ revolutions in 1!} 3, its angular
velucity is about: {a} 0.1?T rsdfs {h} [1211' rsdfs Fﬁv' (I! a?) (2'5) {c} 31W rsdfs F I 99“ $0 in; {:1 nade
(Wm — xv 11. Ten seconds after an electric fan is turned an1 it rntstes st 300 revfmin. Its angular
acceleration {assuming it Was constant) must have been: Iadfs2 a 4—
} 30mm? 0; = a *— 9‘:
'* 93+ {a} 30 Dennis2 {d} 50 revfr’min2 .._. [e] 1801:! 1'wa: d = gig/ﬁg. = ZaaCZF)
mite; T ((951; 12. Three identical objects of mass m. are fastened to s masslsss rod of length L as shown.
The rotational inertia. about one and of the rod of this BITE}! is: H 51} mszal
b] my Clem
c) mLﬁxs !
my.“ [I £ n i a
s] Emir2 l 2 2
_ 7 l.
J = Wmﬂg) + m a.
2; 5
:; le 13. A wheel initially has angular velocity 18 radfsec but is slowing down at a rate of 2 radfsQ.
By the time it stops it will have turned through approximately how many revolutions? (Hint: use '.rr :5 3, like in Indiana}. D
revolutions ﬂag, = Wﬂ cl" Kit
{b} 26 revolutions
5 _r 18 —* 2 'l: [c] 39 revolutions {d} 52 revolutions D
{a} ﬁﬁreyolutlous 9£+wll¥ +ng2 'ﬁ 1: 493:.
I = so says) F 31% = nie height and then roll down an
one is s. solid cylinder, and the \/ 2i ' {its} 14. Three objects are simultaneously released from the an inclined plane without slipping. One is a solid sphere,
third is a hollow cylinder {like a hoop}. All three have the same outer radius and same total mass. Which of the following statements is correct? a All three reach the bottom at the same time.
The sphere reaches the bottom ﬁrst and the hollow cylinder last. {c} The hollow cylinder reaches the bottom ﬁrst and the solid cylinder last.
[d] The hollow cylinder reaches the bottom ﬁrst and the sphere last.
{e} The sphere reaches the bottom ﬁrst and both cylinders srriye together later. 15. A record which has moment of inertia about its oenter In is rotating on a record player
with angular speed as] = 33 rein" min. A. second record, also having moment of inertia
In, and initially not rotating, is dropped onto the ﬁrst. The suri'aces of the two reoords
are not frictionless. 1'What is the ﬁnal angular speed of the tworecord system? “Time I 0.24: lb} isle
is} as
{d} Ewe ._ {E} 4M: 16. The diagram shows a top view of a hinged door initially at rest. A force F is applied
as shown. Which statement oorreetlg,r desorihes the direction of the torque 1‘" and the angular acceleration r32"? ﬁ points up, :3 points up. {1)} '3" points down, 5 points up.
to} 'F points Lip1 :3 points down.
{d 1'" points down. a points down. i
{e} none of these 17. A. massive disk with moment of inertia {rotational inertia} I is initiallg,r not rotatingj but then a constant torque of 2 Nm is applied continuously for I  , after this It] sr the
torque is suﬁent to get the disk moving with angular veil.111, then what must "
he the moment of inertia I of the disk? / om” Pam/1T FF“ {biasesm2 w¥1y57ﬂ+tk+ =3aﬂ {o} l ltgrm2 M ..E
d 211' log1n2 = = 1.
{Egg “gm? of w; /e I /s:.e I [a I”! 4m, ’Z“=:Es£
1:5/5: tgkgﬁj o 18. A 240 N weight is hung from two ropes as shown. What is the tension in the horizontal
rope? {a} 2401s N
[c] eBUN
(a) asatﬁ N
{e} rtﬂﬂfvﬁN 19. A EDD N ball shown is suspended on a string AB and rests against a frictionless vertical
1small. The string makes an angle 31]“ with the wall. The tension force of the string is: {a} sews N {s} issue's N {a} ﬁﬂﬂfﬁN T555 "3:: e
ﬂames N {e} Eiilllli T = 2D. A student has suspended two masses? in] and my, over a massive pulley as shown. She
is holding the mass mg in her hand1 initially at rest. The mass m; :5 1111. After she lets
go of ma, which of the following is true about the kinetic energy {HE} and potential
energy [U] of the objects in this system? Assume the rope does not slip over the pulley. [a] m1 and mg will increase in U,
and the pulley will increase in HE. {b} nth mm and the pulley will increase
in BilElT and my will increase in U. {c} The ICE gained by 7111 will equal the
.; ential energy lost by mg.
, m2, and the pulley will increase
= in HE1 and 1111 will increase in U.
{e} The KE gained by the pulley will equal
the potential energy lost by ma. ...
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Full Document
 Spring '07
 KOPP
 Energy, Force, Kinetic Energy, Mass, Moment Of Inertia, hockey

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