GRADE 12 PHYSICAL SCIENCES: PAPER 1 (PHYSICS) SEPTEMBER 2016

Transcription

1 METRO ENTRL DISTRIT GRDE PHYSIL SIENES: PPER (PHYSIS) SEPTEMER 06 MRKS: 50 TIME: 3 hours This question paper consists of 5 numbered pages and data sheets.

2 Physical Sciences/P WED Metro entral/sep. 06 INSTRUTIONS ND INFORMTION. Write your name on the first page of your RULED 4 PPER or NSWER OOK.. This question paper consists of TEN questions. nswer LL the questions on your RULED 4 PPER or NSWER OOK. 3. Start EH question on a NEW SIDE of your RULED 4 PPER or NSWER OOK. Use OTH sides of the page in order to avoid wasting paper. 4. Number the answers correctly according to the numbering system used in this question paper. 5. From QUESTION onwards, leave ONE line between two sub-questions, for example between QUESTION. and QUESTION.. 6. You may use a non-programmable calculator. 7. You may use appropriate mathematical instruments. 8. You are advised to use the attached DT SHEETS. 9. Show LL formulae and substitutions in LL calculations. 0. Round off your final numerical answers to a minimum of TWO decimal places.. Give brief motivations, discussions, et cetera where required.. Write neatly and legibly.

3 Physical Sciences/P 3 WED Metro entral/sep. 06 QUESTION : MULTIPLE-HOIE QUESTIONS Four options are provided as possible answers to the following questions. Each question has only ONE correct answer. hoose the answer and write only the letter ( D) next to the question number (..0) in the NSWER OOK, for example. E.. n object is falling at a constant speed near the surface of the earth. Which ONE of the following statements regarding this situation is TRUE? The direction of the resultant force acting on the object is upward. The direction of the resultant force acting on the object is downward. There are no forces acting on the object. D The resultant force acting on the object is zero. (). magnet is stuck on a fridge. The following force diagram shows all four forces acting on the magnet. onsider the following two pairs of forces: (i) the normal force and the force of magnetic attraction (ii) the gravitational force and the static frictional force Which of the above pair(s) make up a Newton s third law action-reaction pair of forces? (i) only (ii) only both (i) and (ii) D neither (i) nor (ii) ()

4 Physical Sciences/P 4 WED Metro entral/sep The following velocity-time graph represents the motion of an object moving vertically through the air near the Earth s surface. v m s 0 t s Use the graph to identify the positive direction of motion as well as the significance of time. Positive direction t time the object up hits the ground down hits the ground up reaches a maximum height D down reaches a maximum height ().4 Which ONE of the following statements is equivalent to Newton s Second Law of Motion? The net force experienced by an object is equal to the rate of change of momentum of that object the change in momentum of that object. the impulse experienced by the object. D the momentum of that object. ().5 book is pushed across a rough surface by a force of magnitude while experiencing a frictional force of magnitude. The average constant speed of the book is. Which ONE of the following expressions gives the rate at which the kinetic energy of the book changes? D ()

5 Physical Sciences/P 5 WED Metro entral/sep The Doppler effect will occur when: listener moves around a stationary source of sound in a circle. listener moves in a straight line towards a stationary source of sound. listener and a source of sound are both stationary. D source of sound moves around a stationary listener in a circle. ().7 In the diagram below, Q is a negatively charged object. Q X The direction of the electric field line at Point X is: to the left up to the right D down ().8 How much will it cost to run a 4 W energy-saving light bulb in a 0 V mains circuit for three hours if the cost per kwh is R,? 4 x 3 x 0 cents 0,04 x 3 x 0 cents 0,04 x 3 x cents D 4 x 0 x cents ()

6 Physical Sciences/P 6 WED Metro entral/sep hoose the option that correctly differentiates between an generator and a D motor. D The generator converts mechanical energy to electrical energy with the aid of slip rings. converts electrical energy to mechanical energy with the aid of slip rings. converts electrical energy to mechanical energy with the aid of a split-ring commutator. converts mechanical energy to electrical energy with the aid of slip rings. The D motor converts electrical energy to mechanical energy with the aid of slip rings. converts mechanical energy to electrical energy with the aid of a split-ring commutator. converts mechanical energy to electrical energy with the aid of slip rings. converts electrical energy to mechanical energy with the aid of a split-ring commutator. ().0 The light from an argon discharge tube is analysed. The following line emission spectrum shows two of the spectral lines observed. X Y lower f Higher f The same spectrum, observed on a distant galaxy, appears to have been red shifted. How will the lines appear to shift compared to the above diagram? X will shift left and Y will shift right X will shift right and Y will shift left X and Y will both shift left D X and Y will both shift right () [0]

7 Physical Sciences/P 7 WED Metro entral/sep. 06 QUESTION man applies a constant pulling force on a heavy parcel of mass 50 kg using a light inextensible rope which passes over a light frictionless pulley as shown in the diagram below. The coefficient of static friction between the parcel and the rough table surface is 0,34. The magnitude of the maximum static frictional force is 0 N. Ignore the mass of the rope. T 50 kg. Draw a free-body diagram showing all forces exerted on the parcel. (4). State, in words, Newton s Second Law of Motion. ().3 When the static frictional force is at its maximum, show that the magnitude of the vertical component of the tension force in the rope is 37,06 N. (5).4 Hence, determine the angle ( ) that the rope forms with the horizontal as well as the magnitude of the tension force in the rope (T). (4).5 The man now increases the magnitude of his pulling force. Under the action of this new constant force, the parcel begins to slide horizontally along the table..5. How will the magnitude of the normal force change as the parcel slides across the table surface? State only INRESES, DERESES or REMINS THE SME. ().5. Give a reason for your answer to QUESTION.5.. () [8]

8 Physical Sciences/P 8 WED Metro entral/sep. 06 QUESTION 3 girl is playing in her bedroom with a super bouncy ball which has a mass of 50 g. The girl throws the super bouncy ball straight down towards the ground from an unknown height (h) with a speed of 3 m s -. It hits the ground and bounces straight up past her and it reaches its maximum height 0,6 s after bouncing. Ignore the effects of air friction. t = 0,6 s v = 3 m s - h =? FLOOR 3. alculate the speed with which the ball leaves the floor after bouncing. (3) 3. If the ball loses 5% of its kinetic energy during each bounce, calculate the kinetic energy of the ball just before its first bounce. (4) 3.3 Using energy principles, determine the height from which the girl threw the ball. (3) 3.4 Using the GROUND S REFERENE, sketch a position vs time graph showing the motion of the bouncy ball from the moment the ball is thrown until it reaches its maximum height after the first bounce. (4) [4]

9 Physical Sciences/P 9 WED Metro entral/sep. 06 QUESTION 4 Scientists are investigating the possibility of making use of a subsurface nuclear explosive in order to deflect asteroids from possible collision with the Earth. Such a nuclear explosive was buried beneath the surface of an asteroid of mass 3,6 x 0 9 kg. efore detonation, a stationary astronaut on a nearby spacecraft measured the velocity of the asteroid to be 5 m s - towards the constellation of Orion. When the explosive was detonated the asteroid split into two fragments, and. The explosion projected the two fragments and in opposite directions towards the constellations Orion and Scorpius with speeds of v = 8 m s - and v = m s - respectively. N. ll speeds are measured relative to the spaceship. 5 m s 3,6 0 9 kg 8 m s v m m EFORE FTER m s v 4. State, in words, the principle of conservation of linear momentum. () 4. Show that fragment has a mass of,5 x 0 9 kg. (5) 4.3 Hence determine the impulse experienced by asteroid fragment. (3) 4.4 The two fragments move apart from each other and after some time their centres of mass are 50 km apart. alculate the magnitude of the gravitational force that the two asteroid fragments exert on each other. (4) [4]

10 Physical Sciences/P 0 WED Metro entral/sep. 06 QUESTION 5 skateboarder is practising a sequence of tricks at the local skate park on a halfpipe. The total mass of the skateboarder and skateboard is 75 kg. The skater leaves point,,4 m above the ground. He skates down the ramp towards point. He reaches Point,,6 m above the ground, with a speed of 3,75 m s - just by rolling along and without using his feet to push himself along the half-pipe. The skateboarder has not oiled the wheels of his skateboard for some time, so there is significant friction between the axles and the wheels of the skateboard. 75 kg,4 m,6 m 5. State in words, the work-energy theorem. () 5. alculate the work done by the gravitational force on the skateboarder as he moves from Point to Point. (4) 5.3 Using the work energy theorem, determine the work done by the frictional force exerted on the skateboard. (6) 5.4 The skateboarder thinks about constructing an inclined plane to join Points and to provide an alternative route between these two points. INLINED PLNE,4 m,6 m 5.4. How would the work done by the gravitational force change if he were to roll from Point to Point along the inclined plane instead of following the curved track? nswer only INRESES, DERESES or REMINS THE SME. () 5.4. Explain your answer to QUESTION () [5]

11 Physical Sciences/P WED Metro entral/sep. 06 QUESTION 6 6. police car moves away from an accident scene at a constant speed with its siren on. paramedic at the accident observes a 7% drop in the frequency of the sound of the siren in comparison to when the car was standing still. Speed of sound in air on that day is 335 m s State in words, the Doppler effect. () 6.. alculate the speed of the car. (4) 6. n astronomer on Earth observes the missing frequencies in a line spectrum from a distant galaxy. The frequencies associated with specific elements are all lower than expected. 6.. With what kind of line spectrum is the astronomer working? nswer only SORPTION or EMISSION. () 6.. Identify the type of shift seen by the astronomer. () 6..3 Is the distant galaxy moving towards or away from our Solar System. () [9]

12 Physical Sciences/P WED Metro entral/sep. 06 QUESTION 7 Three charges J, K and L are arranged on a horizontal plane so that angle JKL is a 90 angle. The charges are -4 µ, + µ and +8 µ respectively. J and K are 50 mm apart and K and L are 00 mm apart. J and L are fixed in position while K is free to move. K (+ µ) 00 mm L (+8 µ) 50 mm J (-4 µ) 7. State in words, oulomb s Law. () 7. alculate the magnitude of the electrostatic force between charges J and K. (4) 7.3 Draw a free-body diagram showing the electrostatic forces exerted on K due to charges J and L. lso show on the vector diagram how the net force can be determined (3) 7.4 alculate the magnitude and direction of the net electrostatic force exerted on K due to charges J and L. (4) 7.5 Define, in words, electric field at a point. () 7.6 alculate the magnitude of the net electric field at K. Give your answer in scientific notation. (3) [8]

13 Physical Sciences/P 3 WED Metro entral/sep. 06 QUESTION 8 battery is connected to a circuit with four resistors and two switches as shown in the diagram below. When switch S is open and no current flows, the voltmeter reading across the terminals of the battery is 8 V. R S V r 4 Ω 3 Ω S 4 Ω 8. Write down the term that describes the voltmeter reading when switch S is open. () When both switches are closed, the voltmeter reading decreases by 0,9 V and the ammeter reads 4,5. 8. Write down the term that describes the voltmeter reading when both the switches are closed. () 8.3 alculate the internal resistance of the battery. (3) 8.4 Which of the resistors in parallel carries the largest current? Write down 4 Ω or 3 Ω. Explain your answer. (3) 8.5 alculate the resistance of resistor R. (7) 8.6 Name the one environmental factor that could cause the resistance of R to change. () 8.7 Switch S is now opened. Will the voltmeter reading INRESE, DERESE or STY THE SME? Explain your answer without doing any calculation. (4) [0]

14 Physical Sciences/P 4 WED Metro entral/sep. 06 QUESTION 9 n alternating current () generator installed on a farm produces the following graph of emf against time. 84,8 ε (V) 0,05 0,0 0,5 0,0 Time (s) 9. What is the period for one rotation of the armature of the generator? () 9. alculate the root mean square voltage (V rms ) for this generator. () 9.3 n ohmic light bulb rated 00 V; 40 W is supplied with energy from this generator alculate the resistance of the light bulb. (3) 9.3. Describe the brightness of the light bulb under these conditions. hoose from TOO RIGHT, ORRET RIGHTNESS or TOO DIM. Explain your answer. () 9.4 Draw a graph of current strength vs. time over the same time interval. Do not show any values on the y-axis. () [0]

15 Physical Sciences/P 5 WED Metro entral/sep. 06 QUESTION 0 group of physicists perform an experiment where they shine five different light sources (,,, D and E) onto the platinum cathode of a photocell. They measure the maximum kinetic energies of the ejected photoelectrons and produce the following graph of their results. 5 4 E k, x 0 8 J 3 D E f 0 5 Hz 0. What does the gradient of the above graph represent? () 0. Define the term threshold frequency. () 0.3 Use the -intercept of the graph in order to calculate the work function of the metal. (3) 0.4 In one of the experiments the brightness of one of the light sources was increased. How would this affect (nswer only INRESES, DERESES or REMINS THE SME for both of the following subquestions.) 0.4. the number of electrons ejected per second? () 0.4. the kinetic energy of the ejected electrons? () 0.5 alculate the speed of an ejected electron when light source E is used. (4) [] TOTL: 50

16 Physical Sciences/P 6 WED Metro entral/sep. 06 DT FOR PHYSIL SIENES GRDE PPER (PHYSIS) GEGEWENS VIR FISIESE WETENSKPPE GRD VRESTEL (FISIK) TLE : PHYSIL ONSTNTS/TEL : FISIESE KONSTNTES NME/NM SYMOL/SIMOOL VLUE/WRDE cceleration due to gravity Swaartekragversnelling Universal gravitational constant Universele gravitasiekonstant Speed of light in a vacuum Spoed van lig in 'n vakuum Planck's constant Planck se konstante oulomb's constant oulomb se konstante harge on electron Lading op elektron Electron mass Elektronmassa Mass of the Earth Massa van die arde Radius of the Earth Radius van die arde g 9,8 m s - G 6,67 x N m kg c 3,0 x 0 8 m s - h 6,63 x 0-34 J s k 9,0 x N m e m e M R E TLE : FORMULE/TEL : FORMULES MOTION/EWEGING v v a t v f f i Δx viδt a t or/of -,6 x 0-9 9, x 0-3 kg 5,98 x 0 4 kg 6,38 x 0 6 m Δy v Δt i a t v i v f vi vf vi a x or/of vf vi a y Δx Δt or/of Δy Δt FORE / KRG F net ma p = mv F net t m v w mg p mv f mv i Gmm GM F g r r f k f s(maks ) k N s N WORK ENERGY ND POWER / REID, ENERGIE EN DRYWING W F x cos U mgh or/of E p mgh K mv or/of Ek mv W net K or/of Wnet Ek K K f K i or/of Ek Ekf Eki

17 Physical Sciences/P 7 WED Metro entral/sep. 06 W nc K U or/of Wnc Ek Ep Pave Fv ave P W t WVES, SOUND ND LIGHT/GOLWE, KLNK EN LIG v f T = f v vl fl f E hf or/of E hc s v v s E W o K max or/of E W o E k (max) where/waar E hf and/en W0 hf0 and/en Kmax mv max or/of E k(max) mv max ELETROSTTIS / ELEKTROSTTIK kqq F (k = 9,0 x 0 9 N m - kq ) E (k = 9,0 x 0 9 N m - ) r r F W E V q q Q Q n of/or n e q e URRENT ELETRIITY / STROOMELEKTRISITEIT V R emk( ) I(R r) I r r r... Rs 3 R p r r W = Vq W = VI t W= I R t W= V Δt R... r 3 q I t W P Δt P = VI P = I R V P R LTERNTING URRENT / WISSELSTROOM/ I P max ave VrmsI Irms Pave IrmsR Vmax V V rms rms Pave R rms