TRIAL EXAMINATION 2017

Transcription

1 GRDE 12 TIME: 3 HOURS MRKS: 150 WESTVILLE OYS HIGH PHYSICL SCIENCE TRIL EXMINTION 2017 PPER I EXMINERS: INTERNL MODERTOR: EXTERNL MODERTOR: D Hayes; M ppenah; M llaway Pietersen & C Mo ller N Julius Moodley INSTRUCTIONS ND INFORMTION Write your name and your teacher s name in the appropriate spaces on the NSWER OOK ND QUESTION PPER. nswer LL the questions in the NSWER OOK. nswer QUESTION 1 on one page and start each question on a new page. Non-programmable calculators may be used. ppropriate mathematical instruments may be used. Number the answers correctly according to the numbering system used in this question paper. Data sheets are attached for your use. Give brief motivations, discussions, et cetera where required. ll numerical answers must be written correct to a minimum of two decimal places, unless otherwise stated. Learner s NME Teacher s NME

2 QUESTION 1: MULTIPLE CHOICE QUESTIONS Four possible answers, indicated by,, C and D are given with each question. Each question has only one correct answer. Write down the numbers in a vertical column, in your answer book and next to each number write the letter of the correct answer. 1.1 fire engine drives due west with its siren on. t a certain stage there are four stationary observers (as indicated by x in the diagram below), standing due north, south, east and west of the fire engine respectively. t which of the four points will the frequency of the sound that the observer hears, appear to be HIGHER than that of the source? N x N W x x E E C S x S D W (2) 1.2 n object is projected vertically upwards from the roof of a building and it hits the ground some time later. The effects of air resistance are negligible. The diagram alongside shows the path of the object. Up is taken as the positive direction. Which acceleration-time graph best represents the vertical motion of the object from the time it was projected up until it hits the ground? a + a + C a + D a + 0 t 0 t 0 t 0 t (2) p 2

3 1.3 Which row in the table below correctly gives the energy conversion in the C motor and the component(s) connected to the ends of the coil (armature)? Energy conversion Component(s) Electrical to mechanical Split ring commutator Mechanical to electrical Split ring commutator C Electrical to mechanical Slip ring D Mechanical to electrical Slip ring (2) 1.4 Planet X has a mass M and a radius R. n object has a weight of 160 N on planet X. The same object has a weight of 640 N on another planet Y. Which row in the table below gives the correct mass and radius of planet Y? MSS OF PLNET Y RDIUS OF PLNET Y M 2R 2M R C 4M 2R D 16M 2R (2) 1.5 Two trolleys and move towards each other at the same constant speed v. Trolley has TWICE the mass of trolley. The diagram below represents the situation. m v v 2m fter the trolleys collide, trolley moves to the left with a speed of 1 2 v. ll frictional forces can be ignored. What is the velocity of trolley after the collision? C D 4 v, left 1 4 v, left 2 v, right 1 2 v, left (2) p 3

4 WLL WHS PHYSICL SCIENCE TRIL EXMINTION 2017 PI 1.6 n object X of unknown weight is suspended from the ceiling by a string which makes an angle of 30⁰ with the ceiling. nother string attaches X perpendicular to a wall. The strings are inelastic and have negligible mass. The tensions in the strings are labelled T1 and T2. The diagram below represents the situation. CEILING 30 0 T2 T1 X Which of the following calculations will correctly solve for the magnitude of the weight (Fg) of object X? Fg = T2.sin 30⁰ Fg = T2.cos 30⁰ C Fg = (T2) 2 (T1) 2 D Fg = T1 (2) 1.7 box is pulled in a straight line, a distance Δx, across a rough horizontal surface by means of a rope inclined at an angle θ to the horizontal. constant force F acts along the rope and a constant frictional force f acts between the box and the horizontal surface. F f θ Δx C Which statement below represents the work done by the ROPE on the box in moving it a distance Δx? F.Δx (Fx f).δxcosθ (Fx + f).δxcosθ D F.Δx cosθ (2) p 4

5 1.8 The force between two identical positive point charges is F if they are a distance r from each other. The point charges are now moved so that the force between them becomes 9F. The distance between the charges is now C 1 3 r 3 r 1 9 r D 9 r (2) 1.9 In the circuit diagram below, two resistors R1 and R2 are connected in series and the resistance of resistor R1 is TWICE the resistance of resistor R2. Identical voltmeters V1 and V2 are connected across each resistor. The cell and conducting wires have negligible resistance. V1 V2 R1 R2 If the reading on voltmeter V1 is V then the reading on voltmeter V2 is C D V 1 2 V 2V 1 4 V (2) 1.10 neon tube lights up when a large external voltage is applied across it. Which ONE of the following terms best describes the type of spectrum observed when the gas inside the tube is viewed through a diffraction grating? C Continuous Line emission Line absorption D Electromagnetic (2) [20] p 5

6 QUESTION 2: 1200 kg light weight truck is accelerating at 1,8 m.s -2 up a rough horizontal slope. The angle between the slope and the ground is θ. The kinetic frictional force acting on the truck is N. The magnitude of the force exerted by the engine of the truck is N. The diagram below represents the situation. θ 2.1 State Newton s Second Law of motion in words. (2) 2.2 Draw a LELLED free body diagram showing all the forces acting on the truck as it accelerates up the slope. (4) 2.3 Show that θ is 46,57 ⁰. (5) 2.4 The driver of the truck reduces the force exerted by the engine. The truck then moves, up the inclined road, at CONSTNT VELOCITY. Calculate the magnitude of the new force exerted by the engine of the truck. (2) [13] p 6

7 QUESTION 3: Two blocks and have masses m and 5 kg respectively. The blocks are initially at rest on a frictionless surface and there is a compressed spring between them. Once the spring is released block moves to the LEFT with a velocity of 0,10 m.s -1 and block moves to the RIGHT with a velocity of 0,50 m.s -1. The diagram below represents the situation. WLL m 5 kg 3.1 Calculate the mass of block. (5) 3.2 Write down the definition of impulse. (2) 3.3 lock continues to move at 0,50 m.s -1 until it hits a wall and comes to a stop. The time of contact between the wall and the block is 0,002 seconds Give a reason as to why block hits the wall with a speed of 0,50 m.s -1. (2) Calculate the average force exerted by the wall on block. (5) What is the magnitude and direction of the force that block exerts on the wall? (2) [16] p 7

8 QUESTION 4: man fires a projectile X directly UPWRDS at a velocity of 29,40 m.s -1 from the edge of a cliff of height 100 m. fter some time projectile X lands on the ground below the cliff. elow is a velocitytime graph that represents the motion of projectile X. It is NOT drawn to scale. Ignore all effects of air friction. 29,4 Velocity (m.s -1 ) Time (s) 4.1 Use the graph to determine the time it will take projectile X to reach its maximum height. (1) 4.2 Calculate the maximum height that projectile X will reach OVE the ground. (4) 4.3 In your answer book, sketch the position-time graph for projectile X for time period t = 0 s to t = 6 s. Use the EDGE of the cliff as the reference point for your graph. Your graph must indicate: the time for the projectile to reach its maximum height the time when the projectile falls past the edge of the cliff the position at the maximum height. (4) 4.4 Exactly 1 second after projectile X is fired, another object, projectile Y, is fired from the ground below the cliff upwards at a velocity of 49 m.s -1. Ignore all effects of friction. Calculate the time taken for projectile Y to pass projectile X from the instant it was fired upwards. (7) height of projectile Y at the instant it passed projectile X. (3) [19] p 8

9 QUESTION 5: 5.1 car of mass 1000 kg is travelling at a constant velocity of 72 km.h -1 westwards on a rough level road. The magnitude of the frictional force acting on the car is 250 N. Calculate the power output of the engine of the car. (4) 5.2 steel ball of mass 2 kg is suspended from a string of negligible mass. It is released from rest at point, as shown in the sketch below. t point it is 0,6 m above the ground and has a velocity of magnitude 3 m.s -1. NO air friction acts on the ball while it is moving. D 0,60 m 0,90 m C Write down the principle of conservation of mechanical energy in words. (2) Calculate the speed of the ball when it reaches point C, on the ground. (5) s the steel ball swings through its lowest position at point C it brushes against the ground, which is NOT frictionless. The ball then swings to a maximum height of of 0,90 m to point D Give the definition of a non-conservative force. (2) Write down the NME of one non-conservative force acting on the ball when it swings from through to D. (2) Use energy principles to calculate the work done by the frictional force between the ground and the ball. (6) [21] p 9

10 QUESTION 6: n ambulance, with its siren blaring at a frequency of 100 Hz, is stationary on the side of a road. cyclist cycles past the stationary ambulance at a constant speed. s he passes the ambulance, he hears a change in the pitch of the siren. The difference in the observed frequencies as the cyclist approaches and then moves away from the siren is 5,16 Hz. 6.1 Name the phenomenon that explains this apparent and observable change in frequency. (2) 6.2 Explain why the cyclist detects a sound with a higher frequency than that of the source, when PPROCHING the ambulance. (2) 6.3 If the speed of sound in air is 330 m.s -1, calculate the speed at which the cyclist was moving. (6) [10] p 10

11 QUESTION 7: 7.1 Two identical conducting spheres each carry a charge of 2 μc after they have been brought into contact and then separated from each other again. The charge on one of the two spheres EFORE contact was +6 μc What was the charge on the other sphere before contact? (2) NME the law used to answer question above. (2) 7.2 X and Y are two point charges of +2 nc and +3 nc respectively. They are separated by a distance of 50 mm as shown in the diagram below. Y is directly east of X and R is a point 10 mm west of Y. X (+2 nc) 50 mm R 10 mm Y (+3 nc) W N S E Calculate the number of electrons that were added to or removed from X to give X a charge of +2 nc, if X was originally neutral. (2) Sketch the resultant electric field pattern caused by the point charges X and Y. (3) Calculate the magnitude and direction of the resultant electric field strength at point R, due to both X and Y. (7) test charge of 2 pc is placed at point R and is allowed to accelerate Calculate the net electrostatic force exerted on this test charge at point R. (4) Will the acceleration of this test charge be UNIFORM or NON-UNIFORM as it moves in this electric field? (1) [21] p 11

12 QUESTION 8: n electric circuit is set up as shown in the diagram below. The resistances of the switch S, ammeters and connecting wires are negligible. The voltmeters have very high resistances. The battery has an emf (ε) of 12 V and has an unknown internal resistance r. V1 S r 1 ε = 12 V 20 Ω V Ω X The switch S is CLOSED. The ammeter 2 reads 0,20 and the voltmeter V2 reads 5,50 V. 8.1 Explain what the term emf of a battery. (2) 8.2 Calculate the reading on ammeter 1. (4) 8.3 Calculate the resistance of resistor X. (3) 8.4 Calculate the total external resistance of the circuit. (4) 8.5 Calculate the internal resistance r of the battery. (3) 8.6 Resistor X is replaced by a new resistor of GRETEr resistance than that of X. Will the reading on the voltmeter V1 connected across the terminals of the battery INCRESE, DECRESE or REMIN THE SME? Explain. (4) [20] p 12

13 QUESTION 9: 9.1 The essential components of a simplified DC MOTOR are shown in the diagram below. DC Source When the motor is functioning, the coil rotates in a CLOCKWISE direction, as shown Write down the function of the split-ring commutator. (1) Write down the function of the brushes. (1) What is the direction of the conventional current in the part of the coil labelled? Write down only FROM TO or FROM TO. (1) State ONE way in which this turning effect (torque) can be increased. (1) 9.2 n electric appliance with a power rating of 2000 W is connected to a 230 V rms household mains supply. Calculate the: Peak (maximum) voltage (3) rms current passing through the appliance. (3) [10] TOTL : 150 p 13

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