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Unformatted text preview: 4' Final Exam DLSecm Name (last) 0 (ﬁrm m J StudentlD firstalettersoflastname l Rubric Codes: 1. (30 points) A mass is attached to a spring and is aliowed to slide back and forth in the xdirection
on a smooth surface without friction. The mass is 20 Kg, and the spring has a stiffness constant k=350
N/m. A student pulls the mass from its equilibrium position out to x = +0.25 meters, and then releases it at t=0 seconds. a) (10 pts) Find the solution for the position as a function of time for this case. A: At. 6'; 0/ K: : 0}g5‘./‘(0 f Sihé = l
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E m imaym. MW’STMW‘W‘WHEE’K" Wéwﬁé—fiowdmof‘th 9:; :Lmz c) (10 pts) Find the solution for the velocity as a function of time. Give the numerical
function and draw a figure of the function. Also clearly mark the amplitude and period in the figure. d) (5 pts) What is the maximum velocity, and at what time does it occur? ' Max Weed acct/us at 1‘} T, icy ii: 0.}63, 0749 first 3 letters oi last name P73 Final Exam DI. Sec_____Namemm \é L Rubric Codes: m I Student ID (""0 5%... M. a... 2. (10 points) ’Lindsey,’ a clever cat, has arranged a piece of cardboard to hang out from a table
over the floor below where she waits. She has weighed one end of the cardboard down with a
0.04kg paperweight, 15cm from the Center. The center of the cardboard sits right above the
edge of the table. She has placed a delicious piece of cheese (0.01kg) only 10cm from the same edge. a. Will 'Charles,’ a 0.02kg mouse, be able to walk all the way out to the cheese and eat it
without tipping the cardboard and falling to his doom? You must show the relevant work to justify your answer. Qjm‘w 4W3“ 6’; triage) {LL J0f &m_£4 p) Yg‘ P7,th 2 J“? I W“), , 14m MAA. 4 ﬁltézﬂwte '
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P7B Final Exam DLSec~ Name am) K 2: l [‘RubricCodes: . . __i.__ ﬁrst 3 letters of last name (ﬁrst) Student ID (10 points) A steel rod spans a length of 3.5 meters and has a circular crosssection with a
diameter of 0.04 meters. On one end a Bunsen burner heats the rod to 850 Kelvin, and the
other is placed in contact with an icewater bath, which remains at 273 Kelvin. The thermal conductivity of steel is 25 [W/m k]. What is the heat current density flowing through the rod? a) (Spts) k
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"35 Vt: (mob/m ‘59.. 17:1...“ ., j . _ : cogs. r L g z .— N k ) ' 3", M : W41,  {In What is the total heat current flowing in the rod? LI IN ‘2‘) (“n toamf ’ b) (5 pts) EH:'QHA ll .1 g. l 8’ w “mumm" first 3 letters of last name P78 Final Exam DLSec _ _____ Nameumi K Y «in»
Student ID [ Rubric Codes: . , _ ___ 4. Hal and Mario sit on a MerryGoRound (MGR) while Orin stands on the ground and pushes the
MGR around. Hal, mass in” = 60 kg, sits at radius rH = 0.6 m from the center. Mario, mass mM =
40 kg, sits near the edge at rM = 1.6 m. The radius of the MGR is also R=1.6m, but the MGR is virtually massless, so Mzo. They're all having a great time until Orin pushes so fast that Mario is
about to slip and fall", at an angular velocity of around 25 rpm’s. Orin is merciless and will not
stop the MGR, but he now stands away and watches.
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a) (15 points) Hal would like to help Mario if he could, but he can’t get off the MGR. What can
Hal do to slow down the MGR (he can‘t run because the handlebars are in the way, and he can't touch the ground or any external object)? Explain. 3;! H“! may“ 40 “Ha. DW’Lr (I’JL/ W3 moms/14' oﬂ I‘M—flirt
[kncreﬁje’s/ ADI/ml 156604455; ‘lLL‘L aﬂjwlar Mowen‘fum 52f _’ ,1) gygltm :3 can grad, A) WI“ 0€CC.(CA$:SQ. L 3 J/LJ =tdnrll. I 7 A) WV b) (15 points) Hal, a math whiz, quickly calculates the total angular momentum of Hal and
Mario together, before he moves, to be 324.6 kg m2 rad/s. He thinks he should move either
inwards towards the center or outwards towards the edge to slow the angular velocity of the
system, but is not sure which, so he flips a coin and decides to move outwards to r=1.6m. What is the new rotational velocity (of?
,2 Li : t animal/r 7 ‘,S}‘ir6 = mill/1w; ’r 714144pr P‘Zﬁﬂa‘ljggly DL Sec Name {mo KL If mm) l___ , ~ l StUdent low ﬁrst 3 letters of last name 5. (20 points) Check out the circuit to the right. The
battery is 5V and each of the lightbulbs in the circuit
has a resistance of 20. As drawn. the circuit has a 3,99?
place for another lightbulb to be added and there is a 4'
choice of two different bulbs. One is the same as the
bulbs in the circuit (20) while the other is 60. a. Consider the effect on Bulb #1 that adding the 20 bulb
to the circuit has. In particular, when you do this, wﬂ
Bulb #1 shine a little. bri hter or a littl dimmer or not, change at all? For credit you need to exglain your
choice. (no calculations are needed!) (ﬁg, abrasiv'ﬂrl‘znl’ ((SI3iL4ACL c”); lZzS 3965 pguwn éAJLen 1",»: A Eh A* (Ki lAIL!‘(Gl‘w( Whiting; £4CMQJ¢§ Aalﬂwgu _ M (“4+ prim/{M 53 m éq/k/y/ W a I Al“ 0‘1 39:; (L093 1. mew2,!
b. Now consider adding the 60 bulb to the circuit, instearly of ﬁlé Calcalalt‘gt‘hr‘mtee t ingslffgllfltlleﬁ ‘0 7f ’lg” equivalent resistance of the entire circuit, 2. the current through Bulb #1, and 3. the v0
drop across Bulb #2. You must show the relevant work for credit. Eguivalent Resistance of Current throu h Bulb #1 9529.1! ,.
Vim}; lzvcg Voltage Drop across Bulb #2
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 Fall '10
 Snow
 Physics, Angular Momentum, Angular velocity, hal, Rubric Codes

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