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Unformatted text preview: 0 [U 7L! . Total grade: PH 1110 Summary Homework 4, C Term 2008 Name Section Number ' This assignment is worth 2.5% of your ﬁnal grade and is our recommended means for you to assess
your readiness for Exam 4. It is due in conference on Thursday, February 21, and will be returned
to you in conference on Tuesday, February 26, the day before Exam 4. Please Show your work and
report your answers to no more than three signiﬁcant ﬁgures. Place your answers in the boxes, where provided. This summary homework covers the ﬁrst threeﬁiurths of the material in Study Guide 4. The last page of
this study guide is a noncredit supplementary problem covering the. lost fourth of the material, which you
should solve and bring to conference on Tuesday, February 26, when it Will be discussed. 1a. [5 pts] In Lab 8, you veriﬁed the conditions for static equilibrium. State these conditions here, in
either sentences or equations. «.3
ino 25150 01 EFT0 7‘ ‘)
2+:0 1b. [20 pts] Ifthree forces are acting on the stick that you used in Lab 8, and two forces and their position
vectors are lmown and given below, ﬁnd the third force and the torque that the third force exerts upon
the stiCk, which is in equilibrium. The coordinate system is shown on the sketch for part c).. The ﬁrst
two forces and their position vectors are: [rmq F1 = ( + 2.00 i + 2.00 j) N r1 = 7.00 i cm F2=(—0.700i—1.40j)N r2=10.0icm A . 7 Mr; t—li‘lOKIOrIO—z = —I4>‘/0'1UM .
Mr, wrung: :3 rszo Is= 0 1 1c. [15 pts] Sketch the three force vectors on this diagram in their correct positions. The endtoend
length of the stick is 11.4 cm. in 1 Points earned on this page: ':I . Summary Homework 4, continued. Name 4/“
i
< 3 Section Number 2a. [10 pts] In Lab 9, in a now very familiar arrangement, a string connecting a cart and a hanger went
over a pulley, as in the sketch below on the leﬂz. The pulley has tensions T1 and T2 acting upon it, as
shown below in the center. Write an expression for the total torque vector on the pulley in terms of
the shown variables. Assume no slip between the string and the pulley throughout this problem. A TI Experimental setup Close'up 0f Pulley Trot: 77"” * 2b. [10 pts} Given that the pulley has a moment of inertia of I = 1.00 x 104 kg n12, T1 1 4.40 N, T2 = 4.39
N, and r = 2.50 cm, what is the magnitude of the angular aCceleration of the pulley? Z"?—‘ZP< W tr. ma 2 Id
x 2 ('2: a DA
20. [10 pts] The pulley starts rotaﬁg at t = 0 3. At t = 100 5, through how many radians has it revolved?
e :2 JL oi {,7'
1.
I z. L 2.5“. to 2e. [10 pts} What is the work done on the pulley during this time? ‘
.N, ..__. J. 2 _ .L f”
w " 2. I w; L I we. a»; 1.00 No” (29‘)2  C) pts] What is the angular speed at t = 10.0 s? m] 9 it
eagle) = 2.53/0 2f. [10 pts] If all of the kinetic energy of the pulley were to be converted into raising a 3.00—g mass up from the ﬂoor, to what height h would the mass be lifted?
, ___ ' _h = f. 0 6 m 3 X! 0‘3 X ‘71 3’ ' w = M f) h
2 ' I Points earned on this page: :. \t
," “1. Supplementary Problem on Angular Momentum xii; _ ,
“Lau.) Solve this non—credit problem and bring it to conference on Tuesday, October 9. It is intended to give you
practice on the material in the last part omedy Guide 4. A large turntable with moment of inertia l = 1000 kg m2 spins with angular speed to 2 3.00 rad/s. Person
A, mass mA = 60.0 kg stands at a distance halﬁNay to the outer edge of the turntable, whereas Person B,
mass m3 = 80.0 kg stands right at the outer edge of the turntable, as shown below. The people can be
regarded as point masses for this problem, and the radius of the turntable r = 5.00 m. What is the angular speed of the turntable after person A walks to the center of the tame?
Li 5 L3; .
' "‘ 2*  e(I+an+mn?’)w
(I 4" mAﬂmi + Maneé'u"; a; k M at” e
[£000 4 (go (25)“ 4. 30(szﬂw $0000 + o a WES) J50?
w; 2 3, as a/s Person B jumps oft‘the turntable in a direction parallel to his instantaneous velocity, with speed 5.00 m/s
relative to the ground. What is angular speed of the turntable now? I‘d“Lee
E“ wwmwa) as; S I Na + we
Cteoo +90C7DL3 3.38 :1 [000 a)“: + YOxS‘xf’)"
to g z 9.12 12/5 4: ?erson B now returns to the side of the turntable and stands on the ground. He places his hands on the
side of the tumtable, causing a friction force of 100 N. How many revolutions does the turntable make before coming to rest? . i 2'
7'9 = File 5 Eerwerr
a.
a : J; ((000)08’. I2.) 100K5
g) e‘éé‘O ’5 ‘2 l 0, 5.] AR tie/wiring
' ' 3 I Points earned on this page: ...
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