PHYSICAL SCIENCES: PHYSICS
PAPER 1
GRADE 12 
NSC PAST PAPERS AND MEMOS
FEBRUARY/MARCH 2018

INSTRUCTIONS AND INFORMATION 

1. Write your examination number and centre number in the appropriate spaces  on the ANSWER BOOK. 
2. This question paper consists of 11 questions. Answer ALL the questions in  the ANSWER BOOK. 
3. Start EACH question on a NEW page in the ANSWER BOOK. 
4. Number the answers correctly according to the numbering system used in this  question paper. 
5. Leave ONE line between two subquestions, for example between  QUESTION 2.1 and QUESTION 2.2. 
6. You may use a non-programmable calculator. 
7. You may use appropriate mathematical instruments. 
8. You are advised to use the attached DATA SHEETS. 
9. Show ALL formulae and substitutions in ALL calculations.
10. Round off your FINAL numerical answers to a minimum of TWO decimal  places.
11. Give brief motivations, discussions, et cetera where required. 
12. Write neatly and legibly.

QUESTIONS

QUESTION 1: MULTIPLE-CHOICE QUESTIONS 
Various options are provided as possible answers to the following questions. Choose  the answer and write only the letter (A–D) next to the question number (1.1–1.10) in  the ANSWER BOOK, for example 1.11 D. 
1.1 A constant horizontal force F is applied to a box resting on a horizontal,  frictionless surface.  
Which ONE of the following statements regarding force F is CORRECT? Force F will cause the box to move with … 

1. constant acceleration. 
2. constant velocity.
3. constant kinetic energy. 
4. constant momentum. (2) 

1.2 A block rests on a table. The table stands on a concrete floor. The normal  force is represented by N, as shown in the diagram below. 

Which ONE of the following forces will form an action-reaction pair with the  normal force (N)? 

1. Force of the block on the Earth
2. Force of the block on the table 
3. Force of the table surface on the block 
4. Force of the block on the concrete floor (2) 

1.3 A small stone is dropped from a height y above the ground. It strikes the  ground after time t, as shown in the diagram below.  

Take upwards as the positive direction and the ground as zero reference. Ignore the effects of air resistance. 
Which ONE of the following diagrams shows a correct position-time graph for the motion of the stone? 
(2) 
1.4 Learners perform an experiment using identical trolleys, each of mass m.  The trolleys are arranged, as shown in the diagram below. They are initially at  rest on a frictionless surface and are connected with a compressed, massless  spring. 

When the spring is released it falls vertically down and the single trolley  moves with momentum p to the left. 
The magnitude of the momentum of the two trolleys moving to the right  will be: 

1. 2p 
2. p
3. 1p
   2
4. 1p    (2)
   4 

1.5 A pendulum bob is released from point P above a horizontal surface. At the  lowest point, Q, of its swing, it collides with a stationary block situated on a  frictionless horizontal surface, as shown below. Ignore air friction. 

Which ONE of the following combinations of conservation laws can be used  to calculate the speed of the bob at Q immediately before and after colliding  with the block?  (2) 

1.6 Which ONE of the statements below about the Doppler effect is CORRECT? 

1. The Doppler effect is only applicable to sound waves. 
2. The Doppler effect can be used to explain the expanding universe. 
3. Electrons are ejected from a metal surface by means of the Doppler  effect. 
4. A stationary listener hears a lower pitch of the sound from a siren of an  approaching vehicle because of the Doppler effect. (2) 

1.7 The magnitude of the electrostatic force on a charge Q1 due to another charge Q2 is F. Both charges are now doubled without changing the distance between  them. 
The magnitude of the new electrostatic force on Q1 will be: 

1. F
   2
2. 2F
3. 4F
4. 6F (2) 

1.8 Four identical bulbs, P, Q, R and S, are connected to a cell in a circuit, as  shown below. The cell has negligible internal resistance. 

Which ONE of the following statements about the brightness of bulbs P, Q,  R and S is CORRECT? 

1. P burns brighter than R. 
2. S and Q burn brighter than P and R.  
3. P and R burn brighter than S and Q. 
4. ALL the bulbs burn with the same brightness. (2)

1.9 Which ONE of the energy conversions below takes place when a DC motor is  in operation? 

1. Kinetic to electrical 
2. Heat to mechanical 
3. Mechanical to electrical 
4. Electrical to mechanical (2) 

1.10 In an investigation on the photoelectric effect, the graph of maximum kinetic  energy (E_k(max)) versus frequency (f) was obtained for a certain metal, as  shown below. 

The intercepts, P and Q respectively, represent … 

1. Planck's constant and threshold frequency. 
2. work function and threshold frequency. 
3. threshold frequency and work function. 
4. threshold frequency and Planck's constant. (2) [20] 

QUESTION 2 (Start on a new page.) 
Two boxes, P and Q, resting on a rough horizontal surface, are connected by a light  inextensible string. The boxes have masses 5 kg and 2 kg respectively. A constant  force F, acting at an angle of 30oto the horizontal, is applied to the 5 kg box, as shown  below. 

The two boxes now move to the right at a constant speed of 2 m∙s^-1. 
2.1 State Newton's First Law of Motion in words. (2)
2.2 Draw a labelled free-body diagram for box Q. (4) 
Box P experiences a constant frictional force of 5 N and box Q a constant frictional force of 3 N. 
2.3 Calculate the magnitude of force F. (6)
The string connecting P and Q suddenly breaks after 3 s while force F is still  being applied. 
Learners draw the velocity-time graph for the motion of P and Q before and  after the string breaks, as shown below. 

2.4 Write down the time at which the string breaks. (1) 
2.5 Which portion (X, Y or Z) of the graph represents the motion of box Q, after the string breaks? Use the information in the graph to fully support  the answer. (4) [17] 

QUESTION 3 (Start on a new page.) 
A ball is thrown vertically downwards from the top of a building and bounces a few  times as it hits the ground. The velocity-time graph below describes the motion of the  ball from the time it is thrown, up to a certain time T. 
Take downwards as the positive direction and the ground as zero reference. The graph  is NOT drawn to scale. The effects of air friction are ignored. 

3.1 Write down the speed with which the ball is thrown downwards. (1)
3.2 ALL parts of the graph have the same gradient. Give a reason for this. (2)
3.3 Calculate the:  
3.3.1 Height from which the ball is thrown (3)
3.3.2 Time (T) shown on the graph (4)
3.4 Write down the: 
3.4.1 Time that the ball is in contact with the ground at the first bounce (1) 
3.4.2 Time at which the ball reaches its maximum height after the first  bounce (2) 
3.4.3 Value of X (1) 
3.5 Is the collision of the ball with the ground elastic or inelastic? Give a reason  for the answer using information in the graph. (2) [16]

QUESTION 4 (Start on a new page.) 
The diagram below shows two skateboards, A and B, initially at rest, with a cat  standing on skateboard A. The skateboards are in a straight line, one in front of the  other and a short distance apart. The surface is flat, frictionless and horizontal. 

4.1 State the principle of conservation of linear momentum in words. (2) 
EACH skateboard has a mass of 3,5 kg. The cat, of mass 2,6 kg, jumps  from skateboard A with a horizontal velocity of 3 m∙s-1and lands on skateboard B with  the same velocity of 3 m∙s^-1. 
Refer to the diagram below. 

4.2 Calculate the velocity of skateboard A just after the cat has jumped from it. (5) 
Immediately after the cat has landed, the cat and skateboard B move horizontally to the right at 1,28 m∙s^-1. 
4.3  Calculate the magnitude of the impulse on skateboard B as a result of the  cat's landing. (3) [10]

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 30oto 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 learner at Q. (4) 
5.3 Draw a labelled free-body diagram for the learner while he/she is on  section QR. (3) 
The coefficient of kinetic friction (µk) between the learner and the surface of  section QR is 0,08. 
5.4 Calculate the magnitude of the kinetic frictional force acting on the learner  when the learner is on section QR. (3) 
5.5 Use energy principles to calculate the speed of the learner at point R. (5) [17]

QUESTION 6 (Start on a new page.) 
A police car is moving at a constant speed on a straight horizontal road. The siren of  the car emits sound of constant frequency.  EACH of two observers, A and B, standing some distance apart on the same side of  the road, records the frequency of the detected sound.  Observer A records a frequency of 690 Hz and observer B records a frequency  of 610 Hz.  

6.1 State the Doppler Effect in words. (2) 
6.2 In which direction is the car moving? Choose from TOWARDS A or  AWAY FROM A. Give a reason for the answer. (2) 
6.3 Determine the speed of the police car. Take the speed of sound in air  as 340 m.s^-1. (6) 
6.4 Name ONE application of the Doppler effect. (1) [11]

QUESTION 7 (Start on a new page.) 
Two point charges, P and S, are placed a distance 0,1 m apart. The charge on  P is +1,5 x 10^-9 C and that on S is -2 x 10^-9 C. A third point charge, R, with an unknown positive charge, is placed 0,2 m to the right of  point charge S, as shown in the diagram below. 

7.1 State Coulomb's law in words. (2) 
7.2 Draw a labelled force diagram showing the electrostatic forces acting on  R due to P and S. (2) 
7.3 Calculate the magnitude of the charge on R, if it experiences a net  electrostatic force of 1,27 x 10^-6 N to the left. 
Take forces directed to the right as positive. (7) [11] 

QUESTION 8 (Start on a new page.) 
P is a point 0,5 m from charged sphere A. The electric field at P is 3 x 10⁷ N∙C^-1  directed towards A. Refer to the diagram below. 

8.1 Draw the electric field pattern due to charged sphere A.  Indicate the sign of the charge on the sphere in your diagram. (2) 
8.2 Calculate the magnitude of the charge on sphere A. (3) 
Another charged sphere, B, having an excess of 10⁵ electrons, is now placed  at point P. 
8.3 Calculate the electrostatic force experienced by sphere B. (6) [11]

QUESTION 9 (Start on a new page.) 
9.1 The two graphs below show the relationship between current and potential  difference for two different conductors, X and Y. 

9.1.1 State Ohm's law in words. (2)
9.1.2 Which ONE of the two conductors, X or Y, is ohmic?  Refer to the graph and give a reason for the answer. (2) 
9.2 In the diagram below, a battery with an emf of 6 V and  an internal resistance of 2 Ω, is connected to three resistors P, Q and R.  A voltmeter V is connected across the battery. The ammeter A has a  negligible resistance. 

9.2.1 Calculate the ammeter reading when switch S is closed. (5) 
The switch S is now open. 
9.2.2 Will the ammeter reading in QUESTION 9.2.1 INCREASE,  DECREASE or REMAIN THE SAME? Give a reason for the   answer. (2) 
9.2.3 How will the voltmeter reading now compare with the voltmeter  reading when the switch is closed? Choose from INCREASE,  DECREASE or REMAIN THE SAME. (1) 
9.2.4 Explain the answer to QUESTION 9.2.3. (3) [15] 

QUESTION 10 (Start on a new page.) 
10.1 Learners want to build a small DC motor as a project. Write down THREE essential components that are needed for the building of  the motor. (3) 
10.2 An electrical device with a resistance of 11 Ω is connected to an AC source  with an rms voltage of 240 V. 
10.2.1 Define the term rms voltage. (2) 
10.2.2 Calculate the maximum (peak) current passing through the device. (4) [9]

QUESTION 11 (Start on a new page.) 
11.1 In the diagram below, monochromatic light is incident on the metal plate of a  photocell. A sensitive ammeter shows a reading. 

11.1.1 How does the energy of the photons of the incident light compare  to the work function of the metal plate? Choose from GREATER THAN, LESS THAN or EQUAL TO. Give a reason for the answer. (2) 
11.1.2 When a change is made to the monochromatic light, the reading on  the ammeter increases. A learner makes the following statement with regard to this change: The increase in the ammeter reading is due to an increase in the  energy of the incident photons. Give a reason why this statement is INCORRECT. (2)
11.1.3 What does the photoelectric effect tell us about the nature of light? (1) 
11.2 Ultraviolet radiation is incident on the surface of sodium metal. The threshold  frequency (f0) for sodium is 5,73 x 1014 Hz. The maximum speed of an  electron emitted from the metal surface is 4,19 x105 m∙s-1. 
11.2.1 Define or explain the term threshold frequency. (2) Calculate the: 
11.2.2 Work function of sodium (3) 
11.2.3 Frequency of the incident photon (3) [13] 

TOTAL: 150

DATA FOR PHYSICAL SCIENCES GRADE 12
PAPER 1 (PHYSICS)
TABLE 1: PHYSICAL CONSTANTS

TABLE 2: FORMULAE
MOTION

FORCE

WORK, ENERGY AND POWER

WAVES, SOUND AND LIGHT

ELECTROSTATICS

ALTERNATING CURRENT