# Grade 12 Physical Science Paper 1, Physics September 2015

Tags Grade 12 Physical Science – Paper 1, Physics September 2015

Ex: GR

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PHYSICAL SCIENCE

PAPER 1 - PHYSICS

Sept 2015

MARKS:150(Section A – 20 marks. Section B – 130 marks.)

TIME:3 HOURS

EXAMINER:GR

MODERATOR:PW

INSTRUCTIONS AND INFORMATION

1. Write your exam number in the appropriate space on the ANSWER BOOK.
2. This question paper consists of NINE 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.

SECTION A

INSTRUCTIONS

Four options are provided as possible answers to the following questions. Each question has only ONE correct answer. Write only the letter (A–D) next to the question number (1.1–1.10) in the ANSWER BOOK, for example 1.11 E. Cross out any rough work.

QUESTION 1MULTIPLE CHOICE QUESTIONS

1.1Ziyanda places 4 two-rand coins, one above the other, on a horizontal table. Friction is negligible. She shoots another two-rand coin (X) which strikes the lowest coin horizontally. Coin X displaces and replaces the lowest coin, while all the other coins remain at the same place.

Which ONE of the following laws explains why the top threecoinsare NOT displaced?

ALaw of Conservation of Momentum

BLaw of Conservation of Energy

CNewton's Third Law of Motion

DNewton's First Law of Motion

1.2The graph shows the change in the displacement with time,of a particle moving on a straight track.

Which ONE of the following velocity-time graphs best represents the motion of the particle?

1.3A car, moving at constant velocity with kinetic energy Ek, undergoes a horizontal displacement x in time t. If the car's kinetic energy changes to a value of 2Ek, then in the same time, at the new constant velocity, it will undergo a displacement of …

A4x

Bx

C2x

Dx

1.4A possible unit for the rate of change of momentum is:

ANs

Bkg.m.s-1

Ckg.m.s-2

DN.s-1

1.5A source of sound approaches a stationary listener in a straight line at constant velocity. It passes the listener and moves away from him in the same straight line at the same constant velocity. Which graph represents the frequency of the sound the listener hears?

1.6Electric field strength at a point in an electric field is defined as the ...

Aforce experienced per unit positive charge at that point.

Bforce a charge experiences at that point.

Cwork done in moving a unit positive charge to that point.

Dwork done in moving a charge to that point.

1.7If there is a constant current I in a resistor for a certain time t, the energy transferred to the resistor is W. The experiment is repeated several times for different currents while keeping the resistance of the resistor and time t constant. Which ONE of the following graphs is the best representation of the relationship between W and I?

1.8A rectangular current-carrying coil, PQRS, is placed in a uniform magnetic field with its plane parallel to the field as shown below. The arrows indicate the direction of the conventional current.

When viewed from the position shown, the coil will:

Arotate clockwise.

Bremain stationary.

Crotate anticlockwise.

Drotate clockwise and then anticlockwise.

1.9The diagram below shows light incident on the cathode of a photocell. The ammeter registers a reading. Which ONE of the following correctly describes the relationship between the intensity of the incident light and the ammeter reading?

A / Increases / Increases
B / Increases / Remains the same
C / Increases / Decreases
D / Decreases / Increases

1.10Which of the following would NOT result in the formation of a line emission spectrum?

AWhite light is passed through a cold gas.

BElectrons move from a higher energy level to a lower energy level.

CA high voltage is applied across a discharge tube filled with neon.

DHydrogen gas in the suns atmosphere is heated to 10000 K.

TOTAL FOR SECTION A - 20 marks

SECTION B

1Start EACH question on a NEW page.

2Leave ONE line between two sub questions, for example between QUESTION3.1 and QUESTION 3.2.

3Show the formulae and substitutions in ALL calculations.

QUESTION 2

2.1A horse pulls a cart, C, mass 240 kg, attached to a log of wood, W, mass 80kg, on a horizontal road. W is tied to the back of C by means of an inelastic rope, which is inclined at 30° to the horizontal. The horse applies a horizontal force of 170 N on cart C and the system accelerates at 0,3 m.s-2 to the left. The force of friction on cart C is 40 N. The rope has negligible mass.

2.1.1Draw a free body diagram for cart C, indicating and namingall the forces acting on it. (No values required). (4)

2.1.2Calculate:

2.1.2.1The magnitude of the force which the rope exerts on C.(6)

2.1.2.2The force of friction on W (4)

2.2Earth has a mass of 6 x 1024 kg and an average radius of 6,4 x 106 m. A communication satellite, mass 850 kg, moves in a fixed circular orbit around the earth.

2.2.1Calculate how many kilometres above the earth the satellite moves, if the earth exerts a force of magnitude 7 500N on it in order to keep it in the specified orbit. (5)

2.2.2State in words the law you have applied in 2.2.1.(2)



QUESTION 3

A concrete truck of mass 15000 kg is driving along a level road at a constant speed of 27 m.s-1 (97,2 km.h-1) approaching point P as shown in the diagram below.

At point P the road changes to a constant incline which is sloped at 17,5°. After travellingup the slope for a distance of 130m, its speed has dropped to 12 m.s-1. Assume that the frictional force remains at a constant5 000 N while the truck moves up the hill and that the driving force of the engine remains constant.

3.1State the Work Energy Theorem.(2)

3.2Calculate the work done by the engine of the concrete truck.(7)

3.3Hence, calculate the applied force of the engine.(4)



QUESTION 4

4.1It is said that in the late 1500’s, Galileo performed an experiment that proved when two balls of different masses are dropped, their accelerations are identical.
A different experiment is performed where two identical balls, A and B, are released from a height of 47,3 m above the ground. Assume there is no air friction.

4.1.1Show that the time taken for ball A to reach the ground after being dropped is 3,1 s. (3)

4.1.2If ball B is thrown down 1,4 s after ball A is released, calculate the velocity at which this must be done in order for A and B to reach the ground at the same instant. (4)

4.2A rubber ball with a mass of 80 g, is thrown horizontally with a velocity of 7m.s-1and collides perpendicularly with a wall. The ball rebounds in the opposite direction at 6 m.s-1.

4.2.1Calculate the change of momentum of the ball during the collision.(4)

4.2.2If the collision lasts for 0,02 s, calculate the force the ball experiences during the collision. (3)



QUESTION 5

5.1An experiment is conducted to calculate the velocity at which a cricketer can throw a ball. A cricket ball, mass 160 g, is thrown horizontally at a ball of clay, at X,which is hanging from a string. The ball of clay has a mass of 1,0 kg.

When the cricket ball hits the clay at X, it becomes embedded in the clay. The combination of the clay and cricket ball rises 0,27 m to point Y as shown above. Ignore the effects of air friction and the mass of the string.

5.1.1Explain, in words, the principle of conservation of mechanical energy.(2)

5.1.2Show by calculation that the magnitude of the velocity of the combination at point X is equal to 2,3 m.s-1. (3)

5.1.3State the Principle of Conservation of Momentum.(2)

5.1.4Calculate the magnitude of the velocity with which the cricket ball is thrown.(4)



QUESTION 6

6.1During an experiment to determine the speed of sound, students are given a siren that sounds a single note of frequency 426 Hz. They attach it to a remote controlled car and move it at constant speed past a stationary tape recorder which is mounted in the middle of a runway. The tape recorder records the sound of the siren. The studentsobserve that the pitch of the sound changes as it passes the tape recorder.

6.1.1Name the effect which explains this observation.(1)

6.1.2In one ofthe trials the speed of the remote controlled car was noted as 31km·h-1. Two notes from the siren were recorded: one with a frequency of 437Hz and the other note with a frequency lower than 426Hz.

6.1.2.1Show thatthe speed of 31km.h-1is equal to 8,61 m.s-1.(2)

6.1.2.2Using this information, determine the speed of sound in air.(4)

6.1.2.3Using an equation for the speed of sound, explain why the observed frequencies are respectively higher and lower than the frequency of the source (426Hz). (4)

6.2Evidence for the origin of the universe has been obtained by analysing lightreaching us from bodies in the universe.

6.2.1Name the bodies whose light has provided evidence for the origin of theuniverse. (1)

6.2.2Describe what is observed when the wavelengths of the light from these bodies is analysed. (1)

6.2.3What is the name given to the change in wavelength of the light coming from the bodies you have named in 6.2.1? (1)

6.2.4What does the change in wavelength which you have named in 6.2.3 tell us about the motion of distant galaxies? (1)



QUESTION 7

P is a positive charge of + 4 x10-9 C, mounted on an insulated stand. Charge Q is suspended from a light, inelastic string. P is brought closer to Q which is repelled horizontally until the string makes an angle of 10° with the vertical. The centres of the two charges are now on the same horizontal level and 5 cm apart. The mass of Q is 0,08 g.

7.1What is an electric field?(2)

7.2Calculate the magnitude of the electric field strength at Q, due to the electric field caused by P. (4)

7.3Draw a labelled force diagram indicating all the forces acting on charge Q, as well as the size of at least one angle. (4)

7.4Using the force diagram from 7.3, draw a vector diagram which shows that the resultant of the forces is zero. (2)

7.5Hence determine the magnitude of the electrostatic force exerted on Q. (3)

7.6Calculate the magnitude of the charge on Q. (3)



QUESTION 8 The lamps in the circuit, represented in the diagram, are all identical. The reading on ammeter A1 is 3,00 A and the reading on voltmeter V is 3,15 V. The battery has an internal resistance of 0,80Ω.

8.1Briefly explain why the reading on ammeter A2 is equal to 4,5 A.(3)

8.2Calculate the resistance of lamp L3.(3)

8.3Calculate the emf of the battery.(5)

8.4If the filament in L4 burns out, how would the following be affected? Choose from: REMAIN THE SAME, BECOME ZERO, INCREASE NOTICEABLY or DECREASE NOTICEABLY (but not to zero):

8.4.1Effective resistance of the whole circuit.(1)

8.4.3Lost volts.(1)



QUESTION 9

9.1 The output of an AC generator is shown in the graph below.

A light bulb with an average power rating of 100 W is connected to this generator.

9.1.1Calculate the rms potential difference across the light bulb.(3)

9.1.2Calculate the peak current through the light bulb.(5)

9.1.3The AC generator is replaced with a DC generator. Draw the graph of potential difference vs time for the output of the DC generator. (No numerical values are required for either of the axes.) (2)

9.2 The diagram below shows a generator attached to a wheel of a bicycle.

9.2.1When riding a bicycle, the wheel rotates a magnet near a coil. Explain how a current is induced in the coil. (2)

9.2.2What type of current is produced by this generator?(1)



QUESTION 10

10.1The work function (W0) of three different metals is shown in the table below.

Metal / Work Function (W0) in J
Aluminium / 6,54 x 10-19
Zinc / 6,89 x 10-19
Silver / 7,58 x 10-19

10.1.1Define the term work function of a metal.(2)

10.1.2Give a reason why different metals have different work functions.(2)

10.1.3Light of wavelength 2,3 x 10-7 m is shone onto one of the metals in the table above. The average speed of the emitted electrons is 4,78x 105 m.s-1. Identify the metal by performing relevant calculations. (7)



TOTAL FOR SECTION B - 130 marks

TOTAL 150 MARKS

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