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Unformatted text preview: Preblem 1 I15 paints} I tess a ball straight up, and just as it reaches what weuld have been the tap ef its
trajeetery at peirit A, a ﬁiend ﬂips the gravity switch se that the acceleratien due te
gravity is new ass as2 eraaes. The hall beunces iiiiiiii eff the ceiling, but it is
net very geed rubber, se after it hits the ceiling the ﬁrst thus it enlyr beunees bach
dewn as far as peint E. Then it falls back up te the ceiling and sticks. Peint A is
halfway between the fleer and the ceiling, and peirit E is l_ ef the way dewn frem the
ceiling. Draw the acceleratien [5pts), vcleeity {5pts]
and pesitien {5pts} ef the ball in the y directien
as a functien ef time. Label the plets se we
knew which is which! Take y=tl at the fleet,
with y becerning pesitive upwards. DE} NUT
Switch the ceerdinate system when gravity
switches. Assume I let ge ef the ball at ﬂeer
level (y=ﬂ), and assume that the aetien ef the
switch and the beunce are instantaneeus. esavrtr
ill swli'eH Preblem 3 [3] paints] lSensider three mssea as shewn belew. [1'1] and mg each interact with my. via static
frictien, with the same up The beriaental surface belew m3 is frictieniess. An eatemal ferce Fm acts en mi frem the left and the entire system ef three cennected masses
meves te the right [and ebvieusly accelerates). The idea is te previde a suitable magnitude ef Fm as re prevent beth m1 and mi frem meving with respect te m3 during the aceeleratien, i.e. we den’t want m1 te slide dewn aieng, ner mg te slide “back” aieng m3. Te make life easy, we let ml, [[11 and my all have the same mass m. Gravity g is present. a] [212} pts] Find in terms ef relevant parameters, the pessible range ef Fm which will
allew the desired metien te take place. b] [lﬂ pts] It might be that, ifﬂ, is less than seme critical value uifcrit), ne value ef Fm will allew the desired metien. Give a simple argument why this might be true,
and if se, determine tuterit} in terms ef relevant parameters. Frietienleea Physics TA Sectinn 1, Fall 20114. Pref. A. Lanaara MIDTERM I
Mnnday ﬂctcber 4. race ﬁrm3.1"} pm CLUSED EDGE Gﬂﬂﬂ LUCK! 1. This is a clesed beek exam. Ynu are allnwed tn bring aleng nnly ene 3.5"x l 1”
"cheat sheet,“ pens, pencils, scientiﬁc calculatnr, and blue benlzs. 2. Write ynur name, Discussinn Sectien st. (331 name and sine en the tnp ef all materials
ynu intend tn hand in and want tn be graded. 3. Circle ynur final answers. Shew all yeur werk in the blue beak. If yeu de net shew
relevant wnrk fnr part nf a prnblern, ynu will net be awarded any credit fnr that part, even
iftlte answer is cnrrect. If yeu recngniae that an answer dnes nnt make physical sense,
and ynu dc net have time tn ﬁnd ynur errnr, write that ynu knew that the answer eannnt
he cnrrect and explain why. Fer full credit explain ynur reasening carefully, and shew all
steps. 4. While cleanliness and legibility efynur handwriting will net get ynu extra credit, they
will help tn make sure that ynur answers get the credit they deserve. In case ynu make
mistakes, be sure tn crnss them nut sn they will net be mistaken as ynur answer. 5. Express all numerical results tn 3 signiﬁcant figures. Cress nut any wnrk ynu decide is incerrect, with an explanatien in the margin. Prnblem 1 [3] paints] A car jumps between twn identical ramps en a herieental surface. As shewn in the ﬁgure
helew, the car is launched frem the pnint a en the ﬁrst ramp that is at a distance L frern the landing pnint E en the secend ramp. Beth ramps are tilted with the same angle 'EI
frnm the heriaental. L a] [2D pnints] 1Write equatinns fer the x and y pnsitinn cf the car as a ﬁmctinn nf
time using the launch pnint A as the erigin. b} [lﬂ pnints] Calculate the magnitude ef the initial velncity 1e]. cf the car needed te
cnmplete thejump successfully in terms nf L, B, g. l] t 35 paints] A little has of mass M and a big has at mass 3M are attaehed te twe ends ef a repe R2 t": which runs user a massless, frietienless pulley. The pulley hangs from the eeiling by rape R1. The buses are held tttgether by a nearly niassless rubber band. The eeefﬁeient ef static frietien between the twe boxes is 0.44]. The eeefﬁeient at statie frietien hetween the rubber hand and the masses is very small; just eneugh
ignere the effect on the bones ef the frietienal feree exerted by the to keep it freni slipping eff. Yen can therefere
— rnhhet hand. The system remains at rest. A] [It] [its] 1iiiithat is the magnitude and directien ef the ﬁt etienal feree exerted en the
iittle hes. h},r the big hes? B] (it: paints] What is the tensien in rape Rt? CDNTINUED UN THE NEXT PAGE 2] [35 points} I am ﬂying an airplane tit a oonetent veloeity vp of tilt] route at an angle H of 3D degIeee above the horizontal.
I throw :1 ball into the ﬂjl‘ as I ﬂy. An observer on the ground watches the bell and records that it travels at an initial angle it: of ﬁt} degrees above the horizontal. Some time Inter+ after the hall has stoned down. it hits me in the head.
The plane and 1 together have a mess of lﬂﬂﬂ kg; the hall has a mess of {1.5 ltg. BDHKI A} {It} points} What initial speed vb does the observer on the ground record for the Insult?r E] [It] points} How long does it take between the time I toss the hell and the time I get hooked on the head? CDHTDQUED DH THE NEXT PAGE! * 1] C} [5 pelnte} What is the magnitude and directien ef the force exerted by air en the
airplane? 2} D] {it} points} At what angle weuld I have said that l Ihrew the hell?l ...
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This note was uploaded on 09/16/2009 for the course BIO ENG 100 taught by Professor Headgordon,t. during the Spring '07 term at Berkeley.
 Spring '07
 HeadGordon,T.

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