PHY1015-2009-6-E-1 - UNIVERSITEITSEKSAMENS UNISAE‘...

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Unformatted text preview: UNIVERSITEITSEKSAMENS UNISAE‘ unwersfly of south afnca UNIVERSITY EXAMINATIONS PHY101 5 ( 496767) Maleune 2009 ELEMENTARY MECHANICS (PHYSICS 101) Duration 2 Hours 100 Marks EXAMINERS FIRST PROF ML LEKALA SECOND PROF SA RAKITIANSKI Thrs examination Vpape—r consusts often (1b) pages 0 Th1s examination consists of two sectlons, SECTION A and SECTION B 0 Answer SECTION A (Multlple Chmce) on the exaInlnatlon mark reading sheet 0 AnSWer SECTION B (Written Solutions) 1n the exammation answer book 0 The mark allocatlon for each questlon lS 1nd1cated in brackets to the rlght 0 Use of a non-prograxnmable pocket calculator lS permlss1ble. o The informatlon glven at the end of Sectlon B, may be used w1thout proof SECTION A (Multiple Choice) 1 What 15 the magmtude of the force requlred to accelerate an electron from rest to a speed of 1 50 X107 mfs through a dlstance of 0 0125 m? [The mass of an electron 15 me = 9 11 x 10‘31 kg] 1) 5 47 x 10-22 N 2) 3 56 X 10-19 N 3) 8 20 x 10-” N 4) 8 20 x 10-15 N 5) 164 x 10-14 N (3) [TURN OVER] 2 PHY1015 May / June 2009 2 A car is lnltlally travehng at 50 0 km/h The brakes are applled and the car stops over a d1stance of 35 In What was the magmtude of the car’s acceleratlon whlle 1t was brakmg? 5 71 m/s? (3) 3 A block of mass m on a fIICthIfleSS angular hoop of rachus 1? 15 released from rest at a helght y m R above the horlzontal surface Suppose the block shdes along the 1n51de of the hoop! as shown 1n the dlagram below What 15 the speed of the block at the bottom of the hoop? 1) zero m/s 2) ’U = ng 3) v = 7019/ (QB) 4) U = QQ/R 5) t = 298 (3) [TURN OVER] 3 PHY1015 May/ June 2009 4 A rope exerts a force F on a 20 O—kg crate, as shown 1n the dlagram below The crate starts from rest and accelerates upward at 5 00 111/52 What IS the kmetlc energy of the crate when 1t 15 4 O In above the floorP 5 A rock 18 whirled on the end of a stung 1n 3 horlzontal c1rcle of rachus R W1th constant perlod T If the radlus of the Clrcle lS reduced to R/ 2 whfle the perlod remalns T, what happens to the centrlpetal acceleratlon of the rockP 1 It remams the same 2 It 1ncreases by a factor of 2 4 5 It decreases by a factor of 4 (3) ) ) 3) It Increases by a factor of 4 ) It decreases by a factor of 2 ) [TURN OVER] 4 PHY1015 May/June 2009 6 A statlonary 4-kg shell explodes 1nto three plecos Two of the fragments have a mass of l—kg each and move along the paths shown 1n the dragram wrth a speed of 10 m/s The third fragment moves upward as shown 1n the dlagram below What 15 the speed of the thlrd fragment? 1) 0 m/s 2) 1111/8 3) 5 m/s 4) 10 m/s 5) 20 m/s (3) 7 W hreh one of the followlng statements 15 true concernrng an ob Jest executrng snnple harmonlc m0t10n7 1 2 ) Its velouty 1s never zero ) 3) Its veloelty and acceleramon are Slmultaneously zero ) ) Its acceleramon 1s never zero 4 Its velocrty 1s zero when 1ts acceleratlon 1s a maxrmum 5 Its maxnnurn acceleratron 1s equal to 1ts mammum veloc1ty [TURN OVER] 5 PHY1015 May / June 2009 8 A partlcle 15 accelerated from rest at a rate of 4 m/s2 along a stralght hne Which of the followmg statements accurately descubes the motlon of the partlcle‘? 1 The partlcle travels 4 meters durmg each second 2 The partlcle travels 4 meters durlng the first second only ) l 3) The speed of the partlcle Increases by 4 m/s durrng each second 4) The acceleratlon of the moreases by 4 m/s2 durmg each second J 5 The final volomty of the partrcle Wlll be proportlonal to the dlstance that the partlcle covers (3) 9 The figure below shows a block of mass m at rest on a rough mchned plane The block 15 connected to an obJect of the same mass by a massless rope gomg over a f11ct10nless pulley as shown Let ,us be the coeffiment of statlc fr1ct10n between the block and the plane What IS the magmtude of the statrc fr1ct10nal force actmg on the block? .____\9 [TURN OVER] 6 PHY1015 May/June 2009 10 An EEO-kg man balances a boy on the beam as shown 1n the dlagram below Ignorlng the welght of the beam what 15 the mass of the boy? Total marks for SECTION A: [30] [TURN OVER] 7 PHY1015 May / June 2009 SECTION B (Written Solutions) 1 COnSIder the dlagram below Wthh shous an object lucked horizontally at a speed of 10 m/s from the edge of a chff The ob JGCt strlkes the ground 55 m from the foot of the chff of helght H Neglectmg a1r remstance calculate the magmtude of H (10) 2 An ob JECt welghs 7 84 N when 1n alr whllst 1t welghs 6 86 N when totally submerged 1n water Calculate the (a) buoyant force, and (5) (b) den81ty of the ob Ject (5) 3 State as clearly as possnble the followmg (a) The pr1nc1ple of COIISGIthlOI] of mechanlcal energy (3) (b) The pr1nc1ple of conserx at1on of l1near momentum (3) 4 Calculate the tune 1t takes a plane traveling at a constant tangentlal speed of 110 m/s1 to fly once around a Cll‘Cle whose radlus 1s 2850 m (5) [TURN OVER] 8 PHY1015 May / June 2009 5 A bullet of mass m 15 fired at a speed of 110 1nto a wooden block of mass M The bullet comes to a rest 1n the block The block together w1th the embedded bullet shdes along a horlzontal surface wrth a coeffic1er1t of k1net1r fIICtIOIl ,uk [The Sltuatwn 1s shown 1n the dlagram below ] How far does the block shdes before 1t comes to rest? Express your answer 1n terms of m I'M], U0 {JR and g (10) 6 A ball of welght Wham : 800 N 18 supported by a unlforrn boom of we1ght Whom : 3600 N The system 1s shown 1n the dlagrarn below where the approprlate angles are also shown (21) Draw the free—body dlagram for the boom (b) Calculate the tens10n 1n the support cable f-h‘f‘fifl FPO-th VVV ((3) Calculate the magmtude of the force F‘p exerted on the boom at P 7 An arrplane w1ng 1s de51gned so that the speed of the an across the top of the w1ng 15 251 m/s when the speed of the ant below the w1ng 1s 225 m/s Gwen the denS1ty of the an: as 1 29 kg/m3 calculate the l1ft1ng, force on a w1ng of area '24 0 m2 (8) [TURN OVER] 9 PHY1015 May / J une 2009 8 Two crates are connected by a steel w1re (Young s modulus Y = 2 0 x 1011 N /m2) that passes over a fr1ct10nless and massless pulley, as shown 1n the dlagram below The unstretched length of the w1re IS 1 5 m and Its cross—sectlonal area IS 1 3x 10"5 m2 Determlne the change in length of the were when the crates are acceleratmg Ignore the mass of the new (6) 9 A pendulum clock has a length L1 and a perlod T1 = 0 95 s It is found that when the length 15 adjusted to a new value L2 the period becomes T3 = 1 O 5 Assume the pendulum executes a sunple harmomc motlon and calculate the 1‘8th L2 / L1 (5) Total marks for SECTION B: [70] [TURN OVER] 10 USEFUL INFORMATION IU=U0+at ow=wo+at .Fzgflfigflz 1" Of:% oT=F€ a Impulse = 1311373 2 W17” 1 I __ 1 2 . 1AAEhnear “ E???“ . Fbuoyant = ' 10131111 = 192142712 9 = flwg + w)t f?“ = #st __ A W m ’mv2 If2 = ——r— CLT — T'Cl, _ AL F _ Y 4 mg = TB PEgram} : mqh, [IL/appaer = HI’Lrue _ Fbuuymt - P: + épvi' + 10qu = P2 + §pv§ + pgyz © 1, = @015 + éatz 6 = w01+éot3 fl: = 1”}. FM w I 27'! 02 (Ta = T Z T = Ia _ AK AP_B(%) E=H+wh PEELLSLIL = é’l‘n’l UNISA 2009 PHY1015 May/ June 2009 w : 27rf vT—rw, I = Z’mr2 F=—A'L ...
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This note was uploaded on 08/03/2011 for the course PHYS 1015 taught by Professor Mr.zuma during the Spring '11 term at University of South Africa.

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PHY1015-2009-6-E-1 - UNIVERSITEITSEKSAMENS UNISAE‘...

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