Physical Sciences/P1 Prise 1. Nsc DBE/November 2014 QUESTION 5 (Start on a new page.) 5.1 The diagram below shows a track, ABC. The curved section, AB, is frictionless. The rough horizontal section, BC, is 8 m long. ——_ 8m ———__ B c An object of mass 10 kg is released from point A which is 4 m above the ground. It slides down the track and comes to rest at point C. 5.1.1. State the principle of conservation of mechanical energy in words. 2 5.1.2 Is mechanical energy conserved as the object slides from A to C? Write only YES or NO. a) 5.1.3 Using ENERGY PRINCIPLES only, calculate the magnitude of the frictional force exerted on the object as it moves along BC. 6) 5.2 Amotor pulls a crate of mass 300 kg with a constant force by means of a light inextensible rope running over a light frictionless pulley as shown below. The coefficient of kinetic friction between the crate and the surface of the inclined plane is 0,19. 5.21 Calculate the magnitude of the frictional force acting between the crate and the surface of the inclined plane. (3) The crate moves up the incline at a constant speed of 0,5 ms", 5.2.2 Calculate the average power delivered by the motor while pulling the crate up the incline. 6) [18] Copyright reserved 4 Please tum overDBE/November 2015 whe + Physical Sciences/P 1 Prise " NSC QUESTION § (Start on a new page.) The track for a motorbike race consists of a straight,. horizontal section that is 800 m long, A participant, such as the one in the picture above, rides at a certain average speed and completes the 800 m course in 75 s. To maintain this speed, a constant driving force of 240 N acts on the motorbike. 54 Calculate the average power developed by the motorbike for this motion. Another person practises on the same motorbike on a track with an incline. Starting from rest, the person rides a distance of 450 m up the incline which has a vertical height of 5 m, as shown below. The total frictional force acting on the motorbike is 284 N. The combined mass of rider and motorbike is 300 kg. The average driving force on the motorbike as it moves up the incline is 350 N. Consider the motorbike and rider as a single system. 5.2 Draw a labelled free-body diagram for the motorbike-rider system on the incline. 5.3. State the WORK-ENERGY theorem in words, 5.4 Use energy principles to calculate the speed of the motorbike at the end of the 450 m ride. Copyright reserved Please turn over (3) 4) (2) (6) 115)Physical Sciences/P1 10 DBE/November 2016 NSC QUESTION 5 (Start on a new page.) A pendulum with a bob of mass 5 kg is held stationary at a height h metres above the ground, When released, it collides with a block of mass 2 kg which is stationary at point A. The bob swings past A and comes to rest momentarily at a position % h above the ground, The diagrams below are NOT drawn to scale. Before akg women. Immediately after the collision the 2 kg block begins to move from A to B at a constant speed of 4,95 m-s" Ignore frictional effects and assume that no loss of mechanical energy occurs during the collision, 5.1 Calculate the: 5.1.1 Kinetic energy of the block immediately after the collision @) 5.1.2 Heighth 4) The block moves from point B at a velocity of 4,95 m:s" up a rough inclined plane to point C. The speed of the block at point C is 2 ms", Point C is 0,5 m above the horizontal, as shown in the diagram below. During its motion from B to C a uniform frictional force acts on the block. 05m 5.2 State the work-energy theorem in words. 2 5.3 Use energy principles to calculate the work done by the frictional force when the 2 kg block moves from point B to point C. (4) (13) Copyright reserved 3 Plesse tum overPhysical Sciences/P1 "4 DBE/November 2017 Nsc QUESTION 5 (Start on a new page.) In the diagram below, a 4 kg block lying on a rough horizontal surface is connected to a 6 kg block by a light inextensible string passing over a light frictionless pulley. Initially the blocks are HELD AT REST. 5.1 State the work-energy theorem in words. ey When the blocks are released, the 6 kg block falls through a vertical distance of 1,6 m. 5.2 Drawa labelled free-body diagram for the 6 kg block. @ 53 Calculate the work done by the gravitational force on the 6 kg block. @) The coefficient of kinetic friction between the 4 kg block and the horizontal surface is 0,4. Ignore the effects of air resistance. 54 Use energy principles to calculate the speed of the 6 kg block when it falls through 1,6 m while still attached to the 4 kg block. (6) 2) Copyright reserved 4 Please tum overPhysical Sciencesi/P1 xB MDE/September 2018 QUESTION 5 (Start on a new page) A block with mass 10 kg moves on a rough surface and reaches point A at 12 m+ ‘The surface is horizontal from point A to B and at an incline of 35° from point B to C as shown in the diagram below. 5.1 Define the term kinetic energy. 5.2 Calculate the kinetic energy of the block at point A. The coefficient of kinetic friction (\u.) between the block and the surface ABC is 0,15. 5.3 Calculate the magnitude of the kinetic frictional force on the block while moving from point A to B. 5.4 Calculate the speed of the block at point B. ‘The block moves a distance d up the incline and comes to rest at point C. A kinetic frictional force of 12,04 N acts on the block while it moves from point B to C. 5.5 Draw a labelled free-body diagram for the block while it is moving up the incline BC. 5.6 Explain why the kinetic frictional force on the block is less on surface BC than on surface AB. 5.7 Use energy principles to calculate the distance d. ot Copyright reserved Please turn over (2) 3) (3) (4) 3) a) (6) [24]JECISEPTEMBER 2010) PHYSICAL SCIENCES P1 4 QUESTION 5 (Start on a NEW page.) A steel ball of mass1,5 kg attached to an inextensible string hangs from a ceiling. The ball is held at a height of 3m, at point A, above a horizontal table that has a 1,5 kg crate resting on it. The steel ball is released and it collides with the crate at point B. The collision is ELASTIC. The crate then moves to the left and attains a velocity of 6,2 m.s after moving a certain distance, as shown in the diagram below. 5.1. State the principle of conservation of mechanical energy in words. 2) 5.2 Calculate the work done by the gravitational force in moving the steel ball from point A to B. (3) 5.3. Define the term non-conservative force. 2) 5.4 Calculate the work done by friction in moving the crate. i 3 ce Copyright reserved Please tum over10 Physical Sciences P1 NSC Preparatory Examination September 2019 QUESTION 5 (Start on a new page} A 4 kg box is held stotionary at point P, the top of 2 plane PQR, inclined at aan angle to the horizontal. The portion PQ of the plane is smooth while the Portion QR is rough. 5.1 State the principle of conservation of mechanical energy in words. (2) 5.2 Determine the speed of the box at position Q. 4) 5.3 The box experiences a kinetic frictional force of 15 N as it moves with a CONSTANT VELOCITY, from Q to R, down the plane. 5.3.1 State the Work-Energy Theorem in words. @ 5.3.2 Draw a labelled free-body diagram showing ALL forces acting on the box as it moves from Q to R. re 5.3.3 Use the ENERGY PRINCIPLES to calculate the distance X, between Q and R. 5.4 The angle between the incline and the horizontal Is now increased. How will this increase affect the coefficient of kinatic friction of the box? ‘Write only INCREASE, DECREASE or REMAIN THE SAME, (4) (17) 7 Please Tum Over Copynght Reserved10 PHYSICAL SCIENCES P41 {ECISEPTEMBER 2015) QUESTION 4 (Start on a new page. A boy on a skateboard moves at 5 m.s" to the right towards point A at the bottom of a slope which is 4,6 m high. He is carrying a 4 kg parcel. The total mass of the boy, his skateboard and the parcel is 70 kg. He needs to increase his speed, in order to reach point B at the top of the slope. He decides that if he throws the parcel horizontally, it wll inrease his forward velocity. IGNORE ALL FRICTION. 4.1 \nwhich direction must the boy throw the parcel in order to increase his forward velocity? (TO THE LEFT or TO THE RIGHT) (1) 4.2 Give the name of Newton's law of Motion that you used to obtain your answer in QUESTION 4.1. (1) 4.3 State the Principle of conservation of mechanical energy. (2) 44 Calculate the velocity of the boy immediately after the parcel leaves his hand in order for him to reach the top of the slope at point B. (4) 4.5 Calculate the minimum velocity with which he must throw the parcel in order for him to reach the top of the slope at point B. (4) 4.6 How will the answer in QUESTION 4.4 be affected, if the boy throws the ‘same parcel with higher velocity in the same direction as indicated in QUESTION 4.17 Write down INCREASES, DECREASES or REMAIN THE SAME. Explain your answer. 8) [15] ont toed 8 Pass un over{EC/SEPTEMBER 2015) PHYSICAL SCIENCES P1 ct QUESTION 5 (Start on a new page.) During a fire extinguishing operation, a helicopter remains stationary (hovers) above a dam while filing a bucket with water. The bucket, of mass 80 ka, is filled with 1 600 kg of water. It is lifted vertically upwards through a height of 20 m by a cable at a CONSTANT SPEED of 2 m.s“. The tension in the cable is 17 000 N. Assume there is no sideways motion during the lit. Air friction is NOT ignored. ft 17 000N 5.1 State the work-energy theorem in words. 2) 5.2 Drawa labelled free body diagram showing ALL the forces acting on the bucket of water, while being lifted upwards. (3) 5.3 Use the WORK ENERGY THEOREM to calculate the work done by air friction on the bucket of water after moving through the height of 20m. —_(5) [10] Copyright reserved Please tum over10 PHYSICAL SCIENCES P41 (ECISEPTEMBER 2048) QUESTION 5 (Start on a NEW page.) A hot air balloon of mass 245 kg rises from the ground on a windy day. The wind blows in the direction as shown in the diagram, with a force of 1870 N. The hot air in the balloon provides an upward force of 3 000 N, causing the balloon to rise 12m vertically upwards with a speed of 15 ms" 5.1 Draw labelled free-body diagram showing all forces acting on the balloon. @) 5.2 Calculate the: 5.2.1 Work done by gravitational force (3) 5.2.2 Net work done on the balloon (4) 5.3 State the work-energy theorem in words. (2) 5.4 Use the work-energy theorem to calculate the velocity of the balloon after it has risen 12 m. (3) 15) 10 Copyright reserved Please turn over{SEPTEMBER 2014) PHYSICAL SCIENCES P1 9 QUESTION 5 (Start on a new page.) The diagram below shows a crate of mass 60 kg sliding down a steep slope. The slope makes an angle of 30° with the horizontal. The motion of the crate as it moves down the slope is controlled by a worker using a rope attached to the crate. The rope is held parallel to the slope. The tension in the rope, Fr, is 300 N and a constant frictional force of 50 N acts on the crate as it slides down the slope. | a oN Ww 5.1 Drawa labelled free-body diagram showing the forces parallel to the slope acting on the crate as it moves down the slope. 3) 5.2 State the WORK-ENERGY THEOREM in words. (2) 5.3 The change in kinetic energy of the crate is 450 J as it slides from the top to the bottom of the slope. Use the work-energy theorem to calculate the length of the slope, Ax. (6) 5.4 Calculate the coefficient of kinetic friction on the crate as it moves down the slope. (4) [14] Copyright reserved Mi Please tum over(ECISEPTEMBER 2017) PHYSICAL SCIENCES P4 9 QUESTION 4 (Start on aNEW page.) ‘A4kg box at point A above the horizontal is released and slides down 7 mrom A to C ‘on an incline plane. The inclined plane from point A to B which is 3 m is frictionless whilst the plane from B to C is rough as shown in the diagram. The diagram is not drawn to scale. — 4.1 State the principle of Conservation of Mechanical energy in words. 2) 4.2 Calculate the speed of the box at position B. (4) 4.3 The box experiences a constant kinetic frictional force of 13,6 N as it moves down from B to C. 4.3.1 State the Work-Energy Theorem in words. (2) 4.3.2 Draw a free-body diagram showing ALL forces acting on the box while moving from B to C. (3) 4.3.3 Use the energy principles to calculate the kinetic frictional force between B and C if the speed of the box at position C, the bottom of the plane is 3 ms. (5) 4.4 The angle between the incline and the horizontal is decreased. How will this affect the coefficient of kinetic friction acting on the box? Write only INCREASE; DECREASE or REMAIN THE SAME. (1) [17] Copyright reserved 12 Please turn over8 PHYSICAL SCIENCES P1 {EC/SEPTEMBER 2016) QUESTION 4 (Start on a NEW page.) A box is held stationary at point A, the top of a plane ABC, inclined at an angle to the horizontal. The portion AB of the plane is smooth while the portion BC is rough. 4.1 State the principle of conservation of mechanical energy in words. @) 4.2 Caloulate the speed of the box at position B. (4) 4.3 The box experiences a kinetic frictional force of 14,7 N as it moves with a constant velocity, from B to C, down the plane. 4.3.1. State the Work-Energy Theorem in words. 2) 4.3.2 Draw a free-body diagram showing ALL forces acting on the box atB. (3) 4.3.3. Use the work-energy principle to calculate the distance d, between Band C if the box has a mass of 3 kg. 6) 4.4 The angle between the incline and the horizontal is decreased. How will this decrease affect the coefficient of kinetic friction acting on the box? Write only INCREASE; DECREASE or REMAIN THE SAME. (1) 17] \3 Copyright reserved Please tum overPhysical ScloncesiP4 10 NSC QUESTION 5 The diagram below shows a truck of mass, 12.000 kg free-wheeling, {engine of tho truck does no work on the fuck) tia straight inclined road! of length 25 m. ‘The truck experiences a constant fictional force of magnitude 3 400N as ft moves up the incline. The truck enters the bottom of the incline, point A, with a speed of 25 mis and reaches the top of the incline, point B, with @ speed of 20ms™. 6.1 52 54 5.5 56 State the work-eneray theorem in words. Draw a labelled force diagram showing ail the forces acting on the truck as moves up the incline. Caloutate the net work done on the truck on moving from the bottom of the incline to the top of the ‘incline. What is meant by a non-conservative forse?, Show that the work done by the not-conservative force is — 85 000 4. Hence calculate the height, h, reached by the truck at the top of the incline, rs Copyright Reservad Preparatory Exaraination Septamber 2014 it (6) rey Please Tum Over i iPhysical Sciences/Pt 10 DBE/2014 NSC ~ Grade 12 Exemplar QUESTION 4 (Start on a new page.) Two boys, each of mass m, are standing at the back of a flatbed trolley of mass 4m. The trolley is at rest on a frictionless horizontal surface. The boys jump off simultaneously at one end of the trolley with a horizontal velocity of 2 ms" The trolley moves in the opposite direction. 4.1 Write down the principle of conservation of linear momentum in words. 42 Calculate the final velocity of the trolley. 4.3 The two boys jump off the trolley one at a time. How will the velocity of the trolley compare to that calculated in QUESTION 4.2? Write down only GREATER THAN, SMALLER THAN or EQUAL TO, QUESTION 5 (Start on a new page.) A 3 kg trolley is at rest on a horizontal frictionless surface. A constant horizontal force of 10 N is applied to the trolley over a distance of 2,5 m. When the force is removed at point P, the trolley moves a distance of 10 m up the incline until it reaches the maximum height at point Q. While the trolley moves up the incline, there is a constant frictional force of 2 N acting on it. 5.1 Write down the name of a non-conservative force acting on the trolley as it moves up the incline. 5.2 Drawa labelled free-body diagram showing all the forces acting on the trolley as it moves along the horizontal surface, 5.3 State the WORK-ENERGY THEOREM in words, 5.4 Use the work-energy theorem to calculate the speed of the trolley when it reaches point P. 5.5 Calculate the height, h, that the trolley reaches at point Q. Copyright reserved Please tum over (2) (8) a) it (1) (3) (2) (4) (6) 115]Physical Sciences/P1 14 DBE/2016 SCE QUESTION 5 (Start on a new page.) A 20 kg block is released from rest from the top of a ramp at point A at a construction site as shown in the diagram below. The ramp is inclined at an angle of 30° to the horizontal and its top is at a height of 5 m above the ground, 5m B | 5.1 State the principle of conservation of mechanical energy in words. (2) 5.2 The kinetic frictional force between the 20 kg block and the surface of the ramp is 30 N. Use energy principles to calculate the: 5.2.1 Work done by the kinetic frictional force on the block ) 5.2.2 Speed of the block at point B at the bottom of the ramp 6) 5.3 A100 kg object is pulled up the SAME RAMP at a constant speed of 2 m's by a small motor. The kinetic frictional force between the 100 kg object and the surface of the ramp is 25 N. Calculate the average power delivered by the small motor in the pulling of the object up the incline, (4) M4] \6 Copyright reserved Please turn overPhysical Seiences/Pt 12 Preparatory Examination September 2016 Nsc QUESTION 5 {Start on a new page) A car of mass 1500 kg needs to maintain a constant speed of 10 m.s“, up a hill of height 69,00 m. The hill is inclined at 10,21° to the horizontal. 69,00 m The co-efficient of kinetic friction(.), between the surface of the hill and the tyres of the car is 0,017. 5.1 State the WORK-ENERGY theorem. (2) 5.2 Drawa labelled free body diagram to show alll the forces acting on the-car whilst it is moving up the incline with a constant speed of 10 ms", @) 5.3 Show that the magnitude of the kinetic frictional force that acts on the car is 245,94 N while it moves up the hill. (3) 5.4 Use the WORK-ENERGY theorem to calculate the average power the engine of the car must provide to ensure that the car is able to get up the hill rom A to B whilst maintaining a constant speed of 10 m.s" ) [16] V7 een COUNTBra QUESTION 4 PHYSICAL SCIENCES P41 {SEPTEMBER 2013) (Start on a new page.) ‘5 kg block slides up a rough slope inclined at 16° to the horizontal. The block slides past point A and moves 8,4 m before reaching its maximum height at point B. The velocity-time graph below shows how the velocity of the block changes from the moment it passes point A until it reaches its maximum height at point B. 41 42 43 44 45 4.6 47 v(m.s") t@) Describe the motion of the block from A to B. (2) Use the information from the graph to calculate the change in the kinetic energy of the biook between A and B. (3) Write down the magnitude of net work done on the block between A and B. (1) Write down the work energy theorem in words. (2) Draw a free-body diagram which indicates all the forces acting on the block as it slides from A to B. Label the forces clearly. (3) Caloulate the work done by gravitational force on the block as it moves from point A to point B. (3) Use the work energy theorem to calculate the work done by the frictional force as the block moves from point A to B. (5) [19] \85A 6.2 5.3 54 physical Sciences!P4 4 LimpopoDoE/Soptember 2018 NSC QUESTION 5 (Start on a new page.) The dia e diagram below illustrates a child of mass 20 kg sliding down a fitionless ramp. Define a non-conservative force. @) Use the relationship Wy. = AE» + AE; to show that In the absence of non-conservative forces, mechanical energy is conserved. @) Use the principle of conservation of mechanical energy to calculate the speed of the child on landing at the bottom, at point B. @) ‘The coefficient of kinetic friction between the child and the horizontal surface at the bottom of the ramp, is 0, 2. Ifthe child stops at C, use energy principles to calculate the distance X that the child travels before stopping. 4) 12] \4 Scanned by CamScannerPhysical Scionces/P1 40 DBEINovember 2012 Nsc. QUESTION 5 (Start on a new page.) In order to measure the net force involved during a collision, a car is allowed to collide head-on with a flat, rigid barrier. The resulting crumple distance is measured. The crumple distance is the length by which the car becomes shorter in coming to rest. Before collision After collision In one of the tests, a car of mass 1 200 kg strikes the barrier at a speed of 20 m's. The crumple distance, (x; — x2), is measured as 1,02 m. (Ignore the effects of frictional forces during crumpling,) 5.1 Drawa labelled free-body diagram showing ALL the forces acting on the car during the collision. (3) 5.2 State the work-energy theorem in words. 2) 5.3 Assume that the net force is constant during crumpiing, 5.3.1 USE THE WORK-ENERGY THEOREM to calculate the magnitude of the net force exerted on the car as it is brought to rest during crumpling. (4) 5.3.2 Calculate the time it takes the car to come to rest during crumpling. (4) 13] Copyright reserved Please tum overPhysical Sciences/P1 9 DBE/November 2013 QUESTION 5 (Start on a new page.) A65 kg rigid crate moves from rest down path XYZ as shown below (diagram not drawn to scale). Section XY of the path is frictionless. Assume that the crate moves in a straight line down the path. 5 kg 5.1 State, in words, the principle of the conservation of mechanical energy. (2) 5.2 Use the principle of the conservation of mechanical energy to calculate the speed of the orate when it reaches point Y. (4) On reaching point Y, the crate continues to move down section YZ of the path. It experiences an average frictional force of 10 N and reaches point Z at a speed of 4ms", 5.3 APART FROM FRICTION, write down the names of TWO other forces that act on the crate while it moves down section YZ. 2) 5.4 In which direction does the net force act on the crate as it moves down section YZ? Write down only from 'Y to Z' or from 'Z to Y'. (a) 5.5 Use the WORK-ENERGY THEOREM to calculate the length of section YZ. (6) Another crate of mass 10 kg now moves from point X down path XYZ. 5.6 How will the velocity of this 10 kg crate at point Y compare to that of the 5kg crate at Y? Write down only GREATER THAN, SMALLER THAN or EQUAL TO. (1) [15] 21 Copyright reserved Please turn overPhysical Sciences/P1 10 DBEIFeb,—Mar, 2012 NSC QUESTION 5 (Start on a new page.) A.wooden block of mass 2 kg is released from rest at point P and slides down a curved slope from a vertical height of 2m, as shown in the diagram below. It reaches its lowest position, point Q, at a speed of 5 ms Q 5.1 Define the term gravitational potential energy. 2 5.2 Use the work-energy theorem to calculate the work done by the average frictional force on the wooden block when it reaches point Q. ©) 5.3 Is mechanical energy conserved while the wooden block slides down the slope? Give a reason for the answer. 2 54 The wooden block collides with a stationary crate of mass 9 kg at point Q. After the collision, the crate moves to the right at 1 m:s”! 54.1 Caloulate the magnitude of the velocity of the wooden block immediately after the collision. (4) 5.4.2 The total kinetic energy of the system before the collision is 25 J. Use a calculation to show that the collision between the wooden block and the crate is inelastic. (5) [19] QUESTION 6 (Start on a new page.) An ambulance approaches an accident scene at constant velocity. The siren of the ambulance emits sound waves at a frequency of 980 Hz. A detector at the scene measures the frequency of the emitted sound waves as 1 050 Hz. 6.1 Calculate the speed at which the ambulance approaches the accident scene. Use the speed of sound in air as 340 mss (4) 6.2 Explain why the measured frequency is higher than the frequency of the source. 2 6.3 The principle of the Doppler effect is applied in the Doppler flow meter. State ONE positive impact of the use of the Doppler flow meter on humans, 2) [8] Copyright reserved otou Please turn overPhysical Sciences/P1 8 DBE/Feb.—Mar. 2013 NSC. QUESTION 5 (Start on a new page.) The simplified diagram below shows a slide PQ at a playground. The slide is 3 m long and 1,5 m high. A boy of mass 40 kg and a girl of mass 22 kg stand at the top of the slide at P. The girl accelerates uniformly from rest down the slide. She experiences a constant frictional force of 1,9 N. The boy falls vertically down from the top of the slide through the height PR of 1,5:m. Ignore the effects of air friction. . 1.5m m 30° TR 5.1 Write down the principle of conservation of mechanical energy in words. 5.2 Drawa labelled free-body diagram to show ALL the forces acting on the: 5.2.1 Boy while falling vertically downwards 5.22 Girlas she slides down the slide 5.3 Use the principle of CONSERVATION OF MECHANICAL ENERGY to calculate the speed of the boy when he reaches the ground at R. 5.4 Use the WORK-ENERGY THEOREM to calculate the speed of the girl when she reaches the end of the slide at Q. 5.5 How would the velocity of the girl at Q compare to that of the boy at R if the slide exerts no frictional force on the girl? Write down only GREATER THAN, LESS THAN or EQUAL TO. (2) (1) (3) (4) (5) (1) [16] Copyright reserved 23 Please turn overPhysical SciencesiP1 9 DBE/Feb.~Mar. 2014 NSC QUESTION 5 (Start on a new page.) A loaded truck with a total mass of 5 000 kg travels up a straight incline at a constant velocity of 15 ms”. At the top of the incline, the truck is at a height of 55 m above its starting point. The work done by frictional forces is 8,5x 10*J. (Ignore the rotational effects of the wheels of the truck.) 4 5 000 kg isms 65m 5.1 Define power in words. 5.2 Drawa labelled free-body diagram showing ALL the forces acting on the truck as it moves up the incline. 5.3. Use the WORK-ENERGY THEOREM to calculate the work done by the engine of the truck to get it to the top of the incline. 5.4 Caloulate the average power delivered by the engine of the truck if the truck takes 60 s to reach the top of the incline. The truck now returns down the same incline with a constant velocity of 15 m+ 5.000 kg 5.5 How will the work done by the engine of the truck on reaching the bottom of the incline compare to that calculated in QUESTION 5.3? Write down GREATER THAN, SMALLER THAN or EQUAL TO. Give a reason for the answer. 24 Copyright reserved Please tum over (2) (4) 6) @) (2) [16]Physical SciencesiP1 " DBE/Feb.—Mar, 2015 NSC QUESTION 5 (Start on a new page.) 5 kg block is released from rest from a height of 5 m and slides down a frictionless incline to point P as shown in the diagram below. It then moves along a frictionless horizontal portion PQ and finally moves up a second rough inclined plane. It comes to a stop at point R which is 3 m above the horizontal. P Q The frictional force, which is a non-conservative force, between the surface and the block is 18 N. 5.1 Using ENERGY PRINCIPLES only, calculate the speed of the block at point P, (4) 5.2 Explain why the kinetic energy at point P is the same as that at point Q. 2 5.3 Explain the term non-conservative force. 2 5.4 Calculate the angle (8) of the slope QR. m, Copyright reserved 2s Please tun overPhysical Sciences/P1 10. DBE/Feb.~Mar. 2016 Nsc QUESTION 5 (Start on a new pag A constant force F, applied at an angle of 20° above the horizontal, pulls a 200 kg block, over a distance of 3 m, on a rough, horizontal floor as shown in the diagram below. AFTER BEFORE Rough floor The coefficient of kinetic friction, \44, between the floor surface and the block is 0,2. 5.1 Give a reason why the coefficient of kinetic friction has no units. (1) 5.2 State the work-energy theorem in words. 2) 5.3 Draw a free-body diagram indicating ALL the forces acting on the block while it is being pulled. (4) 5.4 Show that the work done by the kinetic frictional force (Wx) on the block can be written as Wa = (1.176 + 0,205 F) J. (4) 5.5 Calculate the magnitude of the force F that has fo be applied so that the net work done by all forces on the block is zero. (4) (15) QUESTION 6 (Start on a new page.) Reflection of sound waves enables bats to hunt for moths. The sound wave produced by a bat has a frequency of 222 kHz and a wavelength of 1,5 x 10° m. 6.1 Caloulate the speed of this sound wave through the air. (3) 6.2 A stationary bat sends out a sound signal and receives the same signal reflected from a moving moth at a frequency of 230,3 kHz. 6.2.1 _ Is the moth moving TOWARDS or AWAY FROM the bat? (1) 6.2.2 Calculate the magnitude of the velocity of the moth, assuming that the velocity is constant. 6) [10] Copyright reserved 26 Please turn overPhysical SciencesiP1 1 DBEIFeb.—Mar. 2018 NSC. QUESTION 5 (Start on a new page.) A slide, PQR, at an amusement park consists of a curved frictionless section, PQ, and a section, QR, which is rough, straight and inclined at 30° to the horizontal. The starting point, P, is 3 m above point Q. The straight section, QR, is 5 m long. A learner, with mass 50 kg, starting from rest at P, slides down section PQ, then continues down the straight section, QR. 5.1 State the law of conservation of mechanical energy in words. (2) 5.2 Calculate the speed of the leamer at Q. (a) 5.3 Draw a labelled free-body ‘diagram for the learner while he/she is on section QR. (3) The coefficient of kinetic friction (Ix) between the leamer and the surface of section QR is 0,08. 5.4 Calculate the magnitude of the kinetic frictional force acting on the leamer when the leamer is on section QR. 3) 5.5 Use energy principles to calculate the speed of the leamer at point R 6) [17] 27 ‘Copyright reserved Please turn over