Grade 10

BISHOPS

Grade 12Physical Science ExamSeptember 2009

Time: 3 HrsPaper IMarks: 150

Examiners: K Kruger, D Ledwidge

SECTION A

Answer this section on the ANSWER SHEET provided.

Question 1. One-word/ term answersGive ONE word /term for each of the following descriptions. Write the correct word/term next to the question number (1.1 1.5).

1.1. Rate of change of momentum.(1)

1.2. Work done on an object is equal to the change of its ___________________.(1)

1.3. An application of the Doppler Effect which gives evidence of an expanding universe.(1)

1.4. A magenta coloured object which has red light shone onto would seem to be __________ coloured.(1)

1.5. Electromagnetic waves that are used as motion detectors for security systems.(1)

[5]

Question 2. True or FalseIndicate whether the following statements are TRUE or FALSE. Write only true or false next to the question number (2.1 2.5). If the statement is FALSE, write down the corrected statement.

2.1. All collisions in which linear momentum is conserved are called elastic collisions.

2.2. As the area of the plates in a capacitor increases, the capacitance increases.

2.3. Slip rings are used in DC motors to reverse current every 180o rotation.

2.4. The law/rule to determine the direction of induced field in a solenoid when a magnet is inserted into it, is the Right Hand Solenoid Rule.

A ball is thrown vertically upwards and returns to the throwers hand.

2.5. The rate of change of the balls velocity is directed upwards during the motion.

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QUESTION 3. Multiple choice questionsFour possible options are provided as answers to the following questions. Each question has only ONE correct answer. Choose the correct answer and make a X in the box containing the correct letter (A-D) next to the relevant question number (3.1 3.5) on the paper provided.

3.1. (v(m.s-1)t(s)t1)Richard, standing on the balcony of his third floor flat, throws a rugby ball vertically upward to his friend Marcel standing one floor higher. Marcel fails to catch the ball and it consequently drops to the ground below, where it lands after t1s.The sketch graph alongside represents the velocity-time relationship of the balls motion. (Downward direction is positive.)

The shaded area on the graph represents the

A) magnitude of the displacement of the ball.

B) total distance the ball has travelled.

C) maximum height of the ball above the ground.

D) speed with which the ball strikes the ground below.

3.2. Carrie, on the ground floor of a building, watches a glass-fronted lift moving downwards. The magnitude of the acceleration of the lift as it moves downwards is 1,5 ms-2. A passenger, Aimee, inside the lift drops a coin. Relative to Carrie, the magnitude of the acceleration of the coin in ms-2, after being dropped, will be as follows:

A) 0

B) 8,3

C) 9,8

D) 11,3

3.3. When light enters a prism from air, the following happens:

A) The wavelengths of the different colours remain the same.

B) The higher frequency light moves faster.

C) Violet light is refracted the most.

D) Red light has the highest frequency and is refracted the most.

3.4. (V1V2RRRS)The three resistors in the circuit represented below are identical

Ignore internal resistance. When switch S is closed, the readings on voltmeters V1 and V2 will

Voltmeter V1

Voltmeter V2

A)

decrease

Remain unchanged

B)

increase

Remain unchanged

C)

decrease

Become zero

D)

increase

Become zero

3.5. The sketch shows two long oppositely charged parallel plates.

(+ + + + + +)

(X YZ )

( - - - - -)

How will the acceleration of an electron placed at points X, Y and Z compare? The acceleration will be

A)greatest at point X.

B)greatest at point Y.

C )greatest at point Z.

D)the same at X, Y and Z.

[5 x 2 = 10]

[Total Section A: 25]

Section B

Instructions and information

1. Answer Section B on the paper provided.

2. The formulae, substitutions and units must be shown in all calculations.

3. Round off your answers to TWO decimal places unless told otherwise in the specific question.

Question 4 Work, Energy and Power

In an experiment, a 200 g ball is allowed to roll down a curved track (from A) and then up the other side, where it reaches a maximum height at C, as indicated in the diagram below. The slope down (A B) is smooth and may be considered frictionless, while the slope up (B-C) is rough.

(A)

(C)

(B) (B)

(60 cm) (100 cm)

(B)

Measurements show that A is 100 cm vertically above the bottom of the track and C is 60 cm above the bottom of the track.

4.1.Calculate the potential energy of the ball at A, relative to the bottom of the track. (3)

4.2.Calculate the energy lost to friction when the ball reaches C. (5)

4.3.What has happened to the energy lost to friction? (2)

4.4If the ball took 0,5 seconds to move from A to B, calculate the rate of work done for this period. (3)

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Question 5 Equations of motion, Momentum and Impulse

The front-ends of modern cars are designed in the event of a head-on-collision to crumple.A car moves at 20 ms-1 straight East. The driver is wearing his safety belt when the car hits a tree. The front-end crumples by 1,55 m. (The car and the driver therefore continue moving forward for 1,55 m before they come to rest).

5.1 In scientific terms, why are cars today designed to crumple on impact?(3)

5.2 How long will it take for the car to come to rest?(4)

5.3 If the driver has a mass of 72 kg, what is the force exerted by the seatbelt on the driver during the collision?(6)

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Question 6 - Vertical projectile motion

A hot-air balloon is moving upwards at a constant velocity of 8 ms-1. At a height of 240 m above the ground a pair of binoculars falls out of the balloon. Ignore air resistance.

6.1 Draw a rough sketch of the motion of the binoculars after the binoculars were dropped, until they hit the ground. Give an explanation of your chosen motion.(3)

6.2 Calculate the maximum height reached by the binoculars.(5)

6.3 How long does it take for the binoculars to reach the ground?(7)

[15]

Question 7 - Electrical circuits

A battery of emf 24V and of internal resistance r is connected in a circuit as shown below:

(410 6 V1AV224V : rS)

7.1. Show by means of calculation, that the effective resistance of the external resistors in the circuit is 3,2 when the switch is closed.(4)

7.2. With switch S closed, the reading on the ammeter is 6 A. Calculate the readings on:

7.2.1. Voltmeter V1(4)

7.2.2. Voltmeter V2(6)

7.3. Calculate the internal resistance of the battery.(5)

7.4. The switch S is now opened. State, without any further calculations, whether the following would INCREASE, DECREASE or REMAIN THE SAME.

7.4.1. The reading on voltmeter V1(1)

7.4.2. The reading on voltmeter V2(1)

7.4.3. The reading on ammeter (1)

[22]

Question 8 - Doppler effect

While an observer is standing on a bridge, a boat approaches the bridge at a speed of 30 ms-1. A siren goes off on the boat and the sound waves have a frequency of 1250 Hz. The speed of the sound waves through the air is 340 ms-1.

8.1 Determine the observed frequency of the sound waves, as the boat approaches the observer.(5)

8.2 Use your determined values to explain what the observer heard.(2)

[7]

Question 9 - Colour and light

Streetlights radiate bright yellow light with a wavelength of 590 x 10-9 m.

9.1. Determine the frequency of the yellow light.(3)

9.2. How many of these wavelengths fit into 1 mm?(2)

9.3 Determine energy of yellow light.(3)

9.4 How would this compare to the energy of blue light higher or lower? (1)

9.5 Explain why a blue car appears black on a highway which is illuminated by yellow lamps.(3)

9.6 What is the complimentary colour of yellow?(1)

[13]

Question 10 - Electric Fields, Electrostatics and Electrodynamics

The picture alongside shows how the generator on a bicycle works. The circular magnet rotates inside an iron core on which a coil is wound. The magnet rotates when the bicycle wheel turns.

10.1.Use Faradays Law to explain why

10.1.1 an emf is induced in the coil. (2)

10.1.2 the emf increases if the bicycle goes faster. (2)

10.2Jacob conducts an experiment to investigate how the emf produced in the coil varies with the rotation frequency of the magnet. He noticed the coil gets hot as the experiment proceeds. He obtained the following results.

emf (V)

2,0

3,3

4,4

6,3

7,4

8,8

11,0

14,5

Frequency (Hz)

32

55

75

100

120

147

163

210

10.2.1 Identify the dependent variable. (2)

10.2.2 Identify the independent variable. (2)

10.2.3 Name a variable that must be kept constant.