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Unformatted text preview: SaLuTlo/US Total grade: [100 PH 1110 Summary Homework 4, A Term 2007 Name Section Number This assignment is worth 2.5% ofyour ﬁnal grade and is Our recommended means for you to assess
your readiness for Exam 4. It is due in conference on Thursday, October 4‘“, and wiii be returned to
you in conference on Tuesday, October 9th, 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 threefourths ofthe material in Study Guide 4'. The last page of
this study guide is a non—credit supplementary problem covering the last fourth of the material, which you
should solve and bring to conference on Tuesday, October 9'”, when it will be discussed.
a. [5 pts] in Lab 8, you veriﬁed the conditions for static equilibrium. State these conditions here, in
either sentences or equations. Zia=0 J Ear—O «1 2?:0 2“ 7? = 0
lb. [20 pts] if three forces are acting on the stick that you used in Lab 8, and two forces and their position
vectors are known 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), with the
+k vector pointing out of the plane of the paper. The ﬁrst two forces and their position vectors are: F] =(+2.00i +2.00j)N rI =7.00icm
Fz:(—0.700i—ul.40j)N' r2=10.0icm a? 2 "£3301. *3: N
2v 3 ¢ 4 _ 7 TI? $2ka ._1 .. A A A 7? z: W s10“: hum: rt: l‘ialozkurm= 4.3m —o.éo) A;
I It; : O T32 1c. {15 pts] Sketch the three force vectors on this diagram in their correct positions. The end—to—end
length of the stick is i 1.4 cm. ’5. 1 Points earned on this page: I: Summary Homework 4, continued. Name 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 left. The pulley has tensions T1 and T1 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. The +k direction is out of the paper. Assume no slip between the string and the
pulley throughout this problem . TI
Experimental set—up Closeup of pulley ‘
17ml: k 2b. [10 pts] Given that the pulley has a moment ofinertia ofl = 1.00 x 10“1 kg ml, ’l‘] = 4.40 N, T; x 4.39
N, and r = 2.50 cm, what is the magnitude of the angular acceleration of the pulley? z"? :— Id 7
OH; n= I« @4311“ 0.01x2.5‘x/o”2 or= 02.511/5’1
* " ~ W "" I
2c. {10 pts] The pulley starts rotatiﬁcg' at t = 0 s. At t = 10.0 5, through how many radians has it revolved?
9 a at at 151’
’ 2— ; i 2.? (Ii0),; a = I Q 5— f?
2d. [1 0 pts] Whatis the angular speed at t = 10.0 s? 
yd ; of t 2:" 2,3 x16)
03= {L/S' 2e. [10 pts] What is the wirk done on the pulley during this time?
, v S.— i,
' N 7 2, 1:0"; I L I ll '1 L SJ. , '4‘ 2571 O ._
2'°°"’0 ( ) . w= 0,03%;20 2f. [10 pts] If all of the kinetic energy ofthe 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? wr—wtcalu r 2 Points earned on this page: D Supplementary Problem on Angular Momentum 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 ofStudy Guide 4. A large turntable with moment of inertia l = 1000 kg m2 spins with angular speed a) = 3.00 rad/s. Person
A, mass m A x 60.0 kg stands at a distance halfway to the outer edge of the turntable, whereas Person B,
mass m3 = 80.0 kg stands ﬁght 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 In. What is the angular speed of the turntable after person A walks to the center of the table? Li :1”; 1 "00.)
(I + WAR: +""”oﬂ;’rwc' 5' (I4 Mk "M “Mo ’16? 1' D000 + (90 (231.01 4_ Bocg'zﬂgf :(rooo + o + sownJ w?
w); a 3. as .rL/S Person B jumps off 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? L¢;L¥r—
[lea/1.1L; +m5ngg] mg r— I use? + max/R—
[tooo + SOC5')”; 3.38 [000 a)” + 5702‘ng
M495: 7* Person B now returns to the side of the turntable and stands on the ground. He places his hands on the
side of the turntable, causing a friction force of 100 N. How many revolutions does the turntable make before coming to rest? i z_
“re “:— Fn. 6 5 EIwes: Q signagﬂi (2):
: .———"_—“—‘"""“‘
I00 X 5
6 $— géﬂ (2, ll 3: to, 5'1 mas/yew Points earned on this page: E ...
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This note was uploaded on 04/29/2008 for the course PH 1110 taught by Professor Kiel during the Fall '08 term at WPI.
 Fall '08
 Kiel

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