1254611687 2009 Physics Assessment Task

1

Exam Choice

2009

PRELIMINARY COURSE EXAMINATION

Physics

General Instructions

Reading time 5 minutes

Working time 2 hours

Write using black or blue pen

Draw diagrams using pencil

Approved calculators may be used

Write your student number in the space provided

Student Number

Total marks 75

This paper has two parts, Part A and Part B

Part A 15 marks Attempt Questions 1-15 Allow about 30 minutes for this part

Part B 60 marks Attempt Questions 16-31 Allow about 1 hour and 30 minutes for this part

2

Part A 15 marks Attempt Questions 1-15 Allow about 30 minutes for this part

Use the multiple-choice answer sheet.

Select the alternative A,B,C or D that best answers the question. Fill in the response oval completely.

Sample: 2 + 4 = (A) 2 (B) 6 (C) 8 (D) 9

A B C D

If you think you have made a mistake, put a cross through the incorrect answer and fill in the new answer.

A B C D

If you change your mind and have crossed out what you consider to be the correct answer, then indicate the correct answer by writing the word correct and drawing an arrow as follows.

A B C D

correct

3

1 Which wave has the shortest wavelength?

(A) An infra-red wave with a frequency of 6.0 x 1010 Hz. (B) A sound wave of frequency 20 kHz. (C) A water wave with a frequency of 0.5 Hz travelling at 5.0 ms-1. (D) A 100 MHz radio wave.

2 The following wave trace was made on the screen of a CRO when the sweep time was set to 2.0 ms per division.

The period of this wave is:

(A) 6 ms (B) 12 ms (C) 16 ms (D) 4 ms

3 Some parts of the electromagnetic spectrum are NOT used for communication. This is mainly because these parts:

(A) have wavelengths that are too small to detect by any known means. (B) travel too slowly. (C) do not have sufficient energy to travel through air. (D) present a danger to the users.

4

4 Which statement is true whenever refraction is observed as light moves from one medium into another?

(A) Total internal reflection will occur if the angle of incidence is suitable. (B) The light will bend towards the normal. (C) The wavelength of the light will change. (D) The speed of light will remain constant.

5 Increased access to reliable energy has NOT led to:

(A) improved health. (B) less environmental impact. (C) better communications. (D) less manual labour.

6 In the following circuits each of the resistors have different resistances.

In which circuit do all three resistors have a different potential difference across them?

(A) (B)

(C) (D)

globe

5

The following information is for questions 7 and 8:

During an investigation to demonstrate the relationship between current, voltage and power of a model electric heating coil, the apparatus shown in the diagram was set up.

power pack

wires thermometer

beaker with water

heating coil

For three trials, the potential difference across the heating coil and the current flowing through the heating coil was measured, along with other data, and recorded below:

trial number

volume of water (mL)

potential difference

across heating coil (volts)

current through

heating coil (amps)

time taken for water to

increase temperature

by 20 oC (s)

temperature of air in

laboratory when

investigation performed

(oC) 1 200 4.0 0.5 200 23 2 370 10.5 1.25 58 24 3 200 8.0 1.0 ??? 24

7 The missing value for the time taken for the water to increase its temperature by 20 oC in the third trial would be closest to:

(A) 50 s (B) 100 s (C) 200 s (D) 400 s

6

8 The best way to improve the investigations overall validity would be to:

(A) Repeat the experiment 10 times. (B) Time how long it takes for the water to boil. (C) Use the same beaker each time. (D) Have the water at the same temperature at the start of each trial.

9 Which of the following is the best analogy for electric potential difference across a light globe as an electric current flows through it?

(A) A class of students spends $10 each as they walk through a shop. (B) Water is pushed through a meter in a pipe. (C) A builder moves a pile of bricks from one place to another. (D) Ants eat a pool of honey as they walk past it.

10 An earth wire would be of most benefit in preventing electrocution in which faulty appliance?

(A) plastic hair dryer (B) metal dishwasher (C) fluorescent light on ceiling (D) mobile phone charger

7

11 A car journey between two towns, Hillston and Ivanhoe, is recorded on a map. The journey takes a total of 10.0 hours to complete. Ivanhoe is 132 km from Hillston in a direct line. The path taken by the car is shown as a bold line on the map.

Ivanhoe 132 km

Hillston

Possible values for the instantaneous speed recorded at a point on the journey and the average velocity of the journey are:

Instantaneous speed

(km h-1) Average velocity

(km h-1) (A) 13.2 25 (B) 0 13.2 (C) 56 60 (D) 103 90

12 A scuba diver is hovering motionless at a depth of 8.0 m below the surface.

At this point in time, it would be correct to say that:

(A) there are no forces acting on the diver. (B) the net force on the diver is zero. (C) there is an overall downwards force on the diver to keep underwater. (D) the divers weight is zero.

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13 Newtons main contribution to the developing model of the Universe at the time was to:

(A) propose gravity as a mechanism for maintaining observed motions. (B) state that only the planets actually moved through space. (C) propose a heliocentric model.

(D) state that the Sun could not be at the centre of the solar system.

14 Four stars, L, M, N and P were observed and their surface colours determined as shown in the table.

The order of these stars from hottest to coolest is:

(A) L, M, N P (B) M, N, P, L (C) M, P, N, L (D) cannot tell with only this information.

15 Sunspots are related to adverse effects on the Earth from:

(A) the dimming sunlight for a time. (B) causing larger than normal tides. (C) increasing global warming. (D) being associated with the source of solar wind activity.

Star Colour L red M white N orange P yellow

9

Part B 60 marks Attempt Questions 16-31 Allow about 1 hour and 30 minutes for this part.

Answer the questions in the spaces provided. Show all relevant working in questions involving calculations.

Question 16 (4 marks)

A first hand investigation to identify the frequency and wavelength of a sound wave travelling at constant velocity was performed.

(a) Sketch the apparatus which was used to perform this investigation and label the various parts.

(b) Describe the relationship between the frequency and the wavelength of the sound waves that were investigated.

Marks

2

2

10


A long, hollow plastic tube is held between two children so that they can talk into it and hear each other clearly, even though they are many metres away from each other.

With the aid of a diagram, compare how the long, hollow plastic tube conveys sound, to how an optical fibre conveys light.

Marks

3

11


(a) In the space below, sketch both a carrier wave, and the carrier wave after it has been modulated by AM.

(b) Explain why modulation of radio waves is necessary for the transmission of communication over long distances.

Marks

2

2

12


In an investigation to find the refractive index of a new transparent substance, a rectangular block of the substance had the paths of three rays of light traced when they entered the block.

A student drew the results shown below:

i = 30o i = 45o i = 60o

r = 45o r = 34o r = 23o

Find the refractive index of the substance to two decimal places.

Marks

4

13


An investigation was performed in zero gravity to find the mass of a charged particle. The particle was placed between two parallel plates spaced 4.00 cm apart and attached to a 120 volt DC power supply, as shown.

+ + + + + + + +

4.00 cm particle 120 V

- - - - - - - - - -

The charge on the particle is 5.0 x 10-8 C. The force on the particle due to the electric field is found to be 1.5 x 10-4 N.

(a) Find the strength of the electric field between the parallel charged plates.

(b) What extra information would need to be measured from this investigation and what would need to be done in order to find the mass of the particle?

Marks

2

2

14


It is normal for a home to have several separate electric circuits, each with their own circuit breaker or fuse.

(a) Identify two reasons for having separate electric circuits in a home.

(b) Household electric circuits also have built-in safety features to protect the home and its occupants. Identify one such safety feature and describe how it is designed to function to offer protection.


Describe the consequences of a non-zero net force acting on an object.

Marks

2

2

2

15


Advertising for a plasma screen television that operates on a 240V electricity supply has a page of fine print which is reproduced below.

(a) What is the power consumption of this television?

(b) Using your previous answer, or otherwise, calculate the current that is drawn from the power point by this television.

Marks

2

2

Operating cost for electricity consumption = $30.00 per year

cost based on 2000 hours of operation

cost based on electricity charged at $0.15 per kWh

16


A long, straight current-carrying conductor is placed near a bar magnet as shown, looking from above. There is no gravity acting.

I

(a) Describe the shape of the magnetic field around the conductor.

(b) If the apparatus is released and the bar magnet is now free to move, in which manner would the bar magnet move? Explain your answer.

Marks

1

2

N S

17


The passage below describes the motion of a vehicle.

(a) Use the grid below to draw a velocity versus time graph of this motion.

Marks

3

(b) Calculate the total distance travelled by the vehicle during this time.

(c) Determine the acceleration of the vehicle during the first 8.0 s of its motion.

2

2

The vehicle commences from rest and undergoes constant acceleration to reach a speed of 20 m s-1 in 8.0 s. It then continues with a constant speed for 4.0 s before undergoing constant deceleration, coming to a complete stop in a further 6.0 s.

18


A 200 kg space probe fires its rocket motor while in deep space, exerting a force always perpendicular to its velocity. This causes it to accelerate at 2.6 m s-2. The firing of the motor lasts 8.0 seconds.

(a) Determine the force exerted by the space probes rocket motor.

(b) Calculate the increase in the space probes momentum.

(c) Identify the shape of the path of the probe when its rocket motor was firing.


A street outside a school has its speed limit reduced from 70 km h-1 to 40 km h-1.

Describe, quantitatively and qualitatively, how the stopping distance of a vehicle would differ between these two speeds.

Marks

2

2

1

3

19


A partly inflated balloon has dots labelled A, B and C drawn on it as shown.

(a) Describe how the motion of the dots relative to each other as the balloon is inflated can be used to describe the motion of galaxies in the universe.

(b) Identify a limitation of this model.


A light globe that is just visible from a distance of 1.00 km can be observed using a telescope when it is placed on the Moon, a distance of 380 000 km.

How many times brighter does the globe appear to be when it is 1.00 km away compared to when it is on the Moon?

Marks

3

1

A B

C

20


A research laboratory claims that it has found a new form of nuclear radiation never before observed. The laboratory reports that this new form of radiation has the following properties:

can penetrate more than 3 metres of concrete has moderate ionising power is deflected by a magnetic field is deflected by an electric field

Discuss whether this new particle is a form of electromagnetic radiation or a particle. Give your reasoning clearly.


Beta particles are physically the same as electrons, yet they are different in some important ways.

(a) Identify one way that beta particles are different from electrons.

(b) Explain why the ionising power of alpha particles is greater than beta particles.

Marks

3

1

2

Exam Choice

2009 Physics Preliminary Examination. Marking Guidelines and model Answers.

Part A Multiple Choice

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15A C D C B C A D A B B B A C D

Part B16 a.

Marking Criteria MarksSufficient apparatus sketched and labelled so that investigation could be performed properly 2Some appropriate parts of the investigation sketched and/or labelled 1

e.g. (note that question only asks for the sketch of apparatus)

nodes where open-ended glass tube speaker signalparticles settle with fine sand/powder generator

which collects at the nodes16 b.

Marking Criteria MarksComplete relationship described 2Relationship described in a simplistic manner 1

The frequency is inversely proportional to the wavelength OR the product of the frequency and wavelength is constant.

17Marking Criteria Marks

Full description given with similarity to fibre optic described fully; useful diagram included and referred to

3

Method of conveying sound in pipe described 2Method of conveying sound in pipe identified 1

The sound waves reflect off the walls of the pipe and continue to travel down the pipe, trapped. Light undergoes total internal reflection in an optical fibre in a similar fashion trapped in the fibre.

18 a.Marking Criteria Marks

Both a carrier wave and AM modulation correctly depicted 2Either a carrier wave OR a form of modulation is depicted 1

Radio waves have a much higher frequency than human hearing so cannot be converted directly into sound for the communication of voice or music. By superposing the actual communication signal onto the carrier wave, the message etc can be decoded back into sound that humans can hear by the radio receiver, thus enabking long distance transmission and reception of communication.


Correct equations used to find correct values and an average taken correctly to 2dp 4Correct refractive indices found for three instances 3Correct refractive index calculated for one instance 2Snells law identified to attempt to find refractive index OR an average of incorrect values attempted 1

1

sinn

sinsin60sin 451.2247

o

o

ir

sinn

sinsin 45sin341.2645

o

o

ir

sinnsinsin30sin 231.2797

o

o

ir

1.2247 1.2645 1.2797 31.26

. . n=1.26

average

i e


Correct answer with correct number of significant figures 2Correct equation used with subsequent incorrect substitution but answered with correct number of sig figs OR correct answer with incorrect number of significant figures 1

4

8

3 -1 -1

1.5 10 N5.0 10 C3.0 10 N C (or V m )

FE

q

20 b.Marking Criteria Marks

Complete answer provided to find mass 2An aspect identified, e.g. acceleration measured 1

Observation and measurement of the particles acceleration, then use m=F/a to find the mass of the particle.21 a.

Marking Criteria MarksTwo reasons identified 2One reason identified 1

e.g. To allow wires of appropriate thickness/cross section to be used; to allow one circuit at a time to be switched off for work to be done; so if a circuit is overloaded or faulty only that circuit is affected; to limit the chances of fire


Appropriate safety feature identified and function described 2Appropriate safety feature identified 1

e.g. Circuit breaker if current exceeds allowed limit, circuit breaker breaks the circuit to prevent overheating or fire.22

Marking Criteria MarksAppropriate and correct (complete) description given, i.e. always acceleration 2Acceleration identified 1

The object will always undergo acceleration if a net force is acting.23 a.

Marking Criteria MarksCorrect answer obtained 2One part of working is performed correctly 1

total costkWh used = cost per kWh$30.00$0.15

200

kWh usedpower consumption =

time of operation200 kWh2000 h

0.1 kW=100 W


Correct selection of equation and correct substitution from pt (a) 2Correct equation selected 1

2

1002400.42 A

P VIPIV


Correct shape identified - circular 124 b.

Marking Criteria MarksCorrect motion identified with correct explanation 2Correct motion identified 1

The north end of the bar magnet would lift up off the table as the magnetic field from the conductor is directed vertically upwards at that point. The direction of a magnetic field is defined as the direction of the force on a north pole placed at that point.


Graph with stated units; linear scales; correct labelled axes; correct points plotted; points joined correctly 3Graph with TWO of the points below 2Graph with EITHER:

stated units OR correct labelled axes with linear scales OR points plotted and joined correctly

1


Correct calculations to arrive at correct answer 2An appropriate (correct) technique is identified 1

Distance travelled = area under graph1 1= 8 20 4 20 6 202 280 80 60

220 m

(

25 c.Marking Criteria Marks

Correct substitution into correct equation to arrive at correct answer with or without correct units 2Correct definition or equation for acceleration identified 1

3

speed(m s-1)

20

16

12

8

4

01 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 time (s)

-1

-2

change in speedacceleration =

time taken20 m s

8.0 s2.5 m s

26 a.

Marking Criteria MarksCorrect answer with correct unit (N) 2Correct answer 1

F = ma = 200 kg x 2.6 m s-2 = 520 N


Correct substitution into correct equation 2Appropriate equation selected 1

Impulse = Ft = 520 N x 8.0 s = 4.2 x 103 Ns

26 c.Marking Criteria Marks

Correct description given arc of a circle, circular. 1


Comprehensive comparison of stopping distance including reaction time plus component that is a function of speed2 is given.

3

Stopping distances from different speeds are compared using some physics 2A component of stopping distance is identified 1

Stopping distance is a function of reaction time x speed plus a function of the square of the vehicles speed, as its KE = 1/2mv 2. If reaction time is, say, 0.5 s, a car travelling at 70 km/h will travel (70/3.6 x 0.5) or 9.7 m before the brakes are applied. At 40 km/h this is 5.6 m. Then the car travelling at 70 km/h will take more than 3 times the distance to come to a stop than from 40 km/h.


Response shows evidence of deep understanding by thorough description of relative motion of dots and of galaxies with relative rates of motion linked to initial separation

3

Motion of dots is compared to relative recessive motion of galaxies in an expanding universe 2Expanding universe is identified 1

The distance between each of the dots on the balloon increases. The rate of increase in distance is greater the further the dots are apart. This represents the motion of galaxies moving away from each other in the expanding universe the further away they are the faster they are moving away from us.


A limitation identified 1

e.g. The dots on the balloon exist only around the surface of the balloon, not spread throughout the balloon.


Correct answer supplied showing correct working 3Inverse square law is used with error(s) 2Inverse square law is identified in some form 1

Sample answerBrightness ratio = (1/distance ratio)2

= (380 000/1)2 = 1.44 x 1011 times brighter


Discussion with correct conclusion backed by correct reasoning using all available evidence 3Discussion with correct conclusion using some of the available evidence 2Correct conclusion without logical reasoning or use of available evidence 1

4

Penetrating ability means it is like gamma rays e/m wave or must be a very small particle; ionising power similar to a small particle such as beta (electron); deflection by both magnetic and electric fields proves it is a charged particle, therefore: it is probably a small, charged particle.


One difference identified 1

e.g. beta particles originate from the nucleus electrons exist outside of the nucleus31 b.

Marking Criteria MarksFull explanation given using two reasons 2Partial explanation given using one reason 1

Alpha particle are physically much larger and they have much more mass than beta particles and are therefore far more likely to knock an electron out of its orbit in the event of a collision. The chance of a collision is greater due to the larger size of alpha particles.

5

Exam Choice

PHYSICS: Preliminary Exam 2009

Mapping Grid

Question No. Marks Syllabus Ref. Outcomes (P-)1 1 8.2.1 82 1 8.2.2 83 1 8.2.3 84 1 8.2.4 85 1 8.3.1 76 1 8.3.3 97 1 8.3.4 78 1 8.3.4 129 1 8.3.2 7, 9

10 1 8.3.6 711 1 8.4.1 612 1 8.4.2 613 1 8.5.1 1014 1 8.5.3 1015 1 8.5.4 1016 4 8.2.1 8,1217 3 8.2.2 818 4 8.2.3 819 4 8.2.4 820 4 8.3.2 6, 921 4 8.3.3, 8.3.6 3, 7,1122 3 8.4.2 623 4 8.3.4 4, 724 2 8.3.5 625 7 8.4.1 6, 926 5 8.4.2, 8.4.4 6,927 3 8.4.5 3,4, 5, 628 4 8.5.2 1, 2, 1029 3 8.5.3 730 3 8.5.4 2, 1031 3 8.5.4 5, 10

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1254611687 2009 Physics Assessment Task

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