QUESTION 1 - Physical Sciences Break 1.0 – Physical ...€¦ · Web view03/09/2013 · Complete the following statements by filling in the missing word or phrase. 2.1 A voltage

Grade 12PHYSICAL SCIENCES

EXAM PAPER 1Time: 3 hours Marks: 150

INSTRUCTIONS AND INFORMATION

Read the following carefully before answering the questions that follow:

1. Answer ALL the questions.

2. Number the questions exactly as the questions are numbered.

3. Start the answer to each question at the top of a new page.

4. All sketches are to be done in pencil and labelled in ink.

5. Write neatly and legibly.

6. Non-programmable calculators can be used.

7. The diagrams in the question paper are not necessarily drawn to scale.

PHYSICAL SCIENCES 2________________________________________________________________

SECTION A

QUESTION 1

Various possible answers are provided for each question. Write the letter only of the correct answer next to the corresponding number.

1.1 The operation of a motor and a generator are each underpinned by an energy transformation together with Fleming’s hand rule. Which one of the following combinations will be TRUE?

Motor Generator

A Electrical to mechanical; Fleming’s left-hand rule

Mechanical to electrical; Fleming’s right-hand rule

B Mechanical to electrical; Fleming’s right-hand rule

Electrical to mechanical; Fleming’s left-hand rule

C Electrical to mechanical; Fleming’s right-hand rule

Mechanical to electrical; Fleming’s left-hand rule

D Mechanical to electrical; Fleming’s left-hand rule

Electrical to mechanical; Fleming’s right-hand rule

(2)

1.2 When a cathode of a photoelectric cell is illuminated with blue light of frequency f, the electrons emitted have a maximum kinetic energy of Ek. For which one of the following graphs is the relationship between Ek and f best illustrated for the photocell?

(2)

1.3 A metal surface, illuminated by monochromatic light of frequency f and intensity I, emits electrons. Which one of the following will be TRUE for the emission?

A The maximum velocity of the electrons depends on I.

B The maximum velocity of the electrons does not depend on either f or I.

C The maximum velocity of the electrons depends on f.

D The number of electrons emitted per second does not depend on either f or I. (2)


1.4 Town X is 1 500 km east of town Y. On a windless day, a plane flying from town X at a constant velocity of 500 km.h–1, reaches town Y in 3 hours. On another trip, the plane, after having flown for 90 minutes (1 hrs) at 500 km.h–1, suddenly experiences a northerly wind (that is, a wind blowing from the north).

If the plane is still to reach town Y in the prescribed time (3 hrs), what changes, if any, should the pilot make to the magnitude and direction of the flight velocity (air speed) of the plane?

Magnitude of flight velocity (km.h–1) Direction of flight velocity

A remain constant at 500 no change

B remain constant at 500 north of east

C increase to greater than 500 north of east

D increase to greater than 500 south of east

(2)

1.5 A man in a boat wishes to go from a point on the south bank of a river to a point directly opposite it on the north bank. The boat travels through the water at 13 m.s–1 to achieve this. At the same time the water in the river is flowing at 5 m.s–1 due east. The vector diagram which best corresponds with this situation is …

(2)


1.6 Eagles can tuck in their wings and free-fall straight down when diving for fish. In the instance graphically described, the eagle starts its dive from a height where its vertical velocity is zero. Suppose that when the eagle starts its dive, it cannot change its path once committed. For which one of the following graphs will the velocity reached by the eagle in a time t, be given by the area underneath the graph?

(2)

1.7 Two balls, moving towards each other, collide head-on and come to rest immediately after the collision. This is only possible if, before the collision …

A their kinetic energies are identical.

B their speeds are identical.

C their masses are identical.

D the magnitudes of their momenta are identical. (2)

1.8 As waves in a ripple tank pass through two narrow openings alongside each other, a distinctive pattern is formed. The phenomena represented by this pattern are …

A interference and diffraction.

B refraction and interference.

C refraction and reflection.

D refraction and dispersion. (2)


1.9 Which one of the following applications does not illustrate applications of ultrasonic echoes?

A Ultrasonic beams can be used by dentists – the vibrations shake the dirt and plaque off your teeth.

B Opticians can use ultrasound to clean spectacles – water inside a tank is vibrated by ultrasound to shake loose the dirt.

C Milk is vibrated by ultrasound so that bacteria in the milk can be destroyed.

D X-rays used by doctors to inspect broken bones. (2)

1.10 A glass prism disperses white light into a ROYGBIV spectrum because of differences in the speed of light of different frequencies in glass. Which one of the following combinations best describes the dispersion of violet light?

Speed in glass Wavelength Angle of deviation

A Least Shortest Smallest

B Most Longest Smallest

C Least Shortest Largest

D Most Longest Largest

(2)

[20]

QUESTION 2

Complete the following statements by filling in the missing word or phrase.

2.1 A voltage is induced in a conductor when the magnetic field through it changes. This is known as: ________________. (1)

2.2 An object of mass M is at rest at position A as shown.

It rolls down an inclined plane. If the momentum of the object doubles as it speeds up, the kinetic energy is increased ________________ times. (1)


2.3 The SI unit of the expression is the same as that of ____________. (1)

2.4 When a force acts on a body, work will only be done by the force if ____________. (1)

2.5 Photoelectric emission demonstrates that light has a ____________ nature. (1)

[5]

TOTAL FOR SECTION A – 25 marks


SECTION B

QUESTION 3

Electric motors and electric generators both require an active magnetic field and a coil which can rotate.

3.1 What is the motor effect? (2)

3.2 How does one increase the number of rotations that the coil can make per second without causing the motor to “burn out”? Give TWO different possibilities. (4)

Electric motors have many household applications, e.g. a fan heater. Consider the following advertisement for an electric heater. Read the advertisement carefully.

COMPACT HEATER BIG ON HEAT PRODUCTION

The new compact heater is the latest development in heating technology. Although it is far smaller than most other domestic

heaters, it is exceptionally efficient, economical and safe.

IT HEATS A ROOM IN MINUTES

A powerful fan draws in air across a thermistor heating element. This heating element automatically reduces its power consumption as the

temperature increases.

The heater has a maximum output of 1000 W and operates from a 220 V AC supply.

3.3 The advertisement says that the power consumption of the heater decreases as the temperature increases. Using a formula, explain what happens to the current through the heater as the temperature increases. (3)

3.4 What happens to the resistance of the heater as the temperature increases? (1)

3.5 Since the maximum power of the heater is 1000 W, what rating fuse would you recommend as a suitable safety precaution? Support your answer with a simple calculation. (4)

[14]


QUESTION 4

A parachutist is descending towards the ground at a constant velocity of 6,5 m.s–1. At a height of 300 m above the ground, he throws a glass marble with a mass of 40 g vertically upwards at 1,5 m.s–1.

4.1 Calculate the velocity at which the marble was thrown relative to the ground. (2)

4.2 Calculate the velocity with which the marble strikes the ground if air friction is ignored. (4)

4.3 In fact, air resistance plays a significant role. If the marble strikes the ground with a velocity of 60 m.s–1, calculate the work done in overcoming air friction. (5)

4.4 Explain in which of the above cases, with or without air friction, mechanical energy is not conserved. (4)

[15]

QUESTION 5

During a mining operation, gold ore is loaded onto a truck, which runs on a track. The loaded truck has a total mass of 5 000 kg. While being hauled up an incline to the surface, the cable breaks and the truck rolls down the incline. At P, the bottom of the incline, the loaded truck collides with two stationary, empty trucks each with a mass of 1 000 kg. The trucks automatically couple together and move off at a speed of 5 m.s–1. Assume that friction is negligible.

5.1 Show that the velocity of the car at point P is 7 m.s–1. (3)

5.2 Determine the kinetic energy of the loaded truck just before impact. (3)

5.3 Determine the vertical height of the loaded truck before the cable broke. (4)

[10]


QUESTION 6

A child, mass 25 kg, at rest in a boat throws a package out horizontally at a speed of 10 m.s–1. The mass of the boat is 55 kg.

6.1 What is the total momentum of the system before the parcel is thrown? (2)

6.2 Calculate the velocity (magnitude and direction) of the boat immediately after the parcel was thrown. (6)

6.3 Name the law used in 6.2. (2)

[10]


QUESTION 7

The sketch below shows the components of a photocell used in a camera light meter.

Inside the photocell is a substance with a low threshold frequency. When monochromatic red light from a 50 W light bulb strikes the caesium cathode in the photocell, the meter gives a reading.

The 50 W bulb is then replaced with a 100 W bulb. The meter now gives a different reading.

7.1 What is the name given to the phenomenon described? (1)

7.2 What will the effect on the current be? Answer “increases”, “decreases” or “remains the same”. (1)

7.3 What is the proportional effect of the change in power of the light bulb on the magnitude of the current? (1)

7.4 Explain your answer in 7.3 (2)

7.5 Give another application of the phenomenon identified in 7.1 (1)

The wavelength of the red light in the 100 W bulb is 600 nm.

7.6 Calculate the energy of the incident photon. (6)

7.7 What is meant by the work function of the caesium cathode? (2)

7.8 Determine the speed of the photoelectrons if the work function of the metal is 2,8x10–19 J. (6)

[20]


QUESTION 8

Two loudspeakers are 1 m apart. The speakers are emitting sound waves of the same frequency and are in phase. Ignore all reflections from walls, floors, etc. The speed of sound in air is 330 m.s-1.

The crests of each wave are depicted by the curved lines in the sketch above.

8.1 Is it correct to say that the crests of each wave are represented by curved lines? Give a reason for your answer. (3)

8.2 Describe the possible interference that may result when two waves pass simultaneously through the same space. (4)

A person stands 3 m from one speaker emitting a 1 110 Hz sound.

8.3 What is the wavelength of the sound wave? (4)

8.4 Where must the person stand if he wishes to determine destructive interference? Explain your answer concisely. (4)

[15]


QUESTION 9

Consider a police car, siren blaring, moving from rest towards the right. Both observers are on the sidewalk (pavement).

9.1 When the police car is stationary, describe the sound heard by each observer. (2)

9.2 As the police car moves between the two observers, describe the sound heard by each observer. (2)

9.3 What is the name given to the phenomena described in 9.1 and 9.2? (2)

The siren of the police car at rest emits a dominant frequency of 1 600 Hz.

9.4 What frequency will you hear if you are at rest and the police car moves towards you at 25 m.s–1 ? (4)

[10]


QUESTION 10

10.1 The battery in the circuit diagram below has an EMF of 12 V and an unknown internal resistance of r. Voltmeter V1 is connected across the battery and voltmeter V2 is connected across the switch S. The resistance of the connecting wires and the ammeter is negligible.

10.1.1 Write down the respective readings on V1 and V2 when the switch S is open. (2)

Switch S is now closed. The reading on V1 changes to 9 V.

10.1.2 What will the new reading on V2 be? (1)

10.1.3 Calculate the total resistance of the circuit. (4)

10.1.4 Calculate the internal resistance, r, of the battery. (5)

10.2 The circuit below shows two light bulbs X and Y, connected in parallel to a battery with negligible internal resistance. The bulbs are marked 40 W and 60 W respectively. Bulb Y glows brighter than bulb X.

10.2.1 How does the resistance of bulb Y compare to that of bulb X? Use an appropriate equation (or relationship) to explain your answer. (3)

12 62

A

V2

V1

r12V

40 W X

60 W Y


During an experiment a learner connects these two light bulbs in series to the same power supply as shown below. He observes that bulb X now glows brighter than bulb Y.

10.2.2 Use an appropriate equation (or relationship) to explain why bulb X now glows brighter than bulb Y. (3)

[18]

QUESTION 11

Lights in most households are connected in the simplified circuit below. Two light bulbs rated at 100 W; 220 V and 60 W; 220 V respectively are connected to an A.C. source of rms value 220V. The fuse in the circuit can allow a maximum current of 10 A.

11.1 Calculate the peak voltage of the source. (4)

11.2 Calculate the resistance of the 100 W light bulb, when operating at optimal conditions. (4)

11.3 An electric iron, with a power rating of 2 200 W, is now connected across points a and b. Explain, with the aid of a calculation, why this is not advisable. (5)

[13]

TOTAL FOR SECTION B - 125 marks

[TOTAL: 150 marks]

X Y

b

a

100 W 60 W

fuse

Documents

QUESTION 1 - Physical Sciences Break 1.0 – Physical ...€¦ · Web view03/09/2013 · Complete the following statements by filling in the missing word or phrase. 2.1 A voltage