PHYSICS Unit 1 and 2

Western Australian Certificate of Education

Practice Examination

Question/ Answer Booklet

PHYSICS Unit 1 and 2

Time allowed for this paper

Reading time before commencing work: ten minutes

Working time for paper: three hours

Materials required/recommended for this paper

To be provided by the supervisor

This Question/Answer Booklet

Formulae and Data Booklet

To be provided by the candidate

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Special items: up to three non-programmable calculators approved for use in the WACE

examinations, drawing templates, drawing compass and a protractor

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PHYSICS Unit 1 and 2 2 PRACTICE EXAMINATION

This exam paper and the solutions are available from www.stepupineducation.com

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Structure of this paper

Section Number of questions available

Number of questions to be answered

Suggested working time

(minutes)

Marks available

Percentage of exam

Section One: Short response

14 14 50 54 30

Section Two: Problem-solving

7 7 90 90 50

Section Three: Comprehension

2 2 40 36 20

Total 100

Instructions to candidates

When calculating numerical answers, show your working or reasoning clearly. Give final

answers to three significant figures and include appropriate units where applicable.

When estimating numerical answers, show your working or reasoning clearly. Give final answers

to a maximum of two significant figures and include appropriate units where applicable.

PRACTICE EXAMINATION 3 PHYSICS Unit 1 and 2


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Section One: Short response 30% (54 Marks)

This section has 14 questions. Answer all questions. Write your answers in the spaces provided.

When calculating numerical answers, show your working or reasoning clearly. Give final answers to

three significant figures and include appropriate units where applicable.

When estimating numerical answers, show your working or reasoning clearly. Give final answers to a

maximum of two significant figures and include appropriate units where applicable.

Suggested working time: 50 minutes.

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Question 1 (3 marks)

According to the kinetic theory of matter, define what temperature is and explain why the lowest

temperature is -273 0C.


A team of huskies pull an 86.0 kg sled, which is initially at rest, until it reaches 16.0 kmh-1 and has

moved 28.5 m through the snow. Calculate the average force the huskies apply to the sled.



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The stability of a nucleus is determined by the balance of forces acting between its nucleons. State

the two forces which act within the nucleus and whether each of these forces would be considered

as an attraction or repulsion force.


Fill in the missing symbols and numbers for each of the nuclear reactions shown below.

𝑅𝑎88226 → 𝑅𝑛____

222 + ____

𝐼53131 → 𝑋𝑒54

___ + ____ + ____

𝑇𝑐4399𝑚 → 𝑇𝑐43

99 + ____


A sound meter detects a 1.80 Wm-2 sound, measured 12.3 m from a speaker. Calculate how far the

sound meter would need to be moved towards the speaker so that it would detect 4.30 Wm-2.



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Using any amount of 7.00 Ω, 10.0 Ω and/or 24.0 Ω resistors, draw a circuit diagram showing how

these resistors can form an equivalent resistance of 29.0 Ω. Use calculations to support your answer.


Passive electrical safety devices, including double insulation and earth wires help isolate live

components from the user. Other devices are useful for detecting when an electrical fault has

occurred and responding to the fault. State the name of one of these devices. Describe how this

device performs its function. Be specific under what circumstances this device is useful.



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The bowling ball below is moving at a steady speed along a smooth bowling alley floor towards the

right of the page. Draw and label a free body diagram showing the physical forces acting on the

bowling ball.


Calculate the mass of ice at 0.00 0C required to reduce the temperature of 3.00 L of water by 15.0 0C,

down to 22.0 0C.



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An off ramp of a freeway is a location where motorists can leave the freeway. These locations pose a

hazard because the road splits and unwary motorists may not be prepared for the changed

conditions.

One way to minimise the consequences of a collision at the off ramp is to install multiple free

standing, plastic barrels filled with water. Motorists who misjudge the road conditions will collide

with the barrels instead of trees or other solid obstacles. Explain why colliding with multiple water

barrels can help minimise the consequences of a collision.

Freeway Traffic

Off Ramp Traffic

Barrels



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Draw the 3rd harmonic standing wave pattern for an open pipe and for a closed pipe into the space

provided below.


A pebble is dropped into the centre of a wave tank and an image of the ripples that spread out are

shown in the diagram below, 1.50 s after the pebble hit the water. Determine the velocity,

wavelength, frequency and period of this wave.

2.30 m



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A radioactive tracer falls from 22.6 Bq to 1.41 Bq over 2.30 hours. Calculate the half life of the

radioactive tracer in minutes


With the aid of a circuit diagram showing both globes and switches, explain the benefit of installing

household lights in parallel. Refer specifically to the flow of current within the parallel circuit.

End of Section 1



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Section Two: Problem-solving 50% (90 Marks)

This section has 7 questions. Answer all questions. Write your answers in the spaces provided.






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A 1.20 kg iron saucepan (specific heat capacity of 450 J kg K-1) filled with 1.50 L of water is placed

onto a 3200 W stove top. The ambient temperature of the room is 18.0 0C. The stove is turned on

and after a while the water begins to boil.

a) Using your hand to grab the saucepan from the cupboard where it was stored, the rubber

handle feels warmer than the iron. Explain this sensation. (2 marks)

b) During heating, bubbles start to form in the water at the base of the saucepan. What are the

bubbles filled with? (1 mark)



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c) Name and describe the mechanism which causes the surface of the water to increase in

temperature. (3 marks)

d) Calculate the amount of heat energy required to increase the water up to its boiling

temperature. (2 marks)

e) Calculate the amount of heat energy required to increase the iron saucepan from ambient

room temperature to 100 0C. (2 marks)

f) Find the theoretical amount of time that it would take to bring the water to the boil.

(2 marks)

g) In reality, the time is much greater than your answer to part f. Suggest a reason why.

(1 mark)



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An 1850 kg car is moving at 66.0 kmh-1 when its driver must apply the brakes hard in an attempt to

not hit the rear of a 1100 kg car which is stopped 18.0 m ahead. The brakes apply 1.24 × 104 N of

retardation force.

a) At what speed does the heavy car collide with the lighter car? (4 marks)

b) After the collision, the heavy car rolls forward at only 30.0% of the speed it had just prior to

the collision. What velocity does the lighter car have after the collision? (3 marks)



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c) Was this collision elastic? Justify your response. (4 marks)

d) After the collision, both cars will eventually come to stop. Has momentum been conserved?

Explain. (1 mark)

e) The lighter car moves 4.20 m forward because of the collision before coming to a stop.

Calculate the average frictional force acting on the lighter car after the collision. (2 marks)



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Radioactive materials are used in industry for monitoring and control. Industrial gamma radiography

exploits the properties of gamma radiation to take an image of welded metal joints. A capsule

contains a pellet of a gamma radioisotope which produces 0.603 W of gamma rays. The capsule is

placed on one side of a metal joint and a photographic screen, sensitive to gamma radiation, is

placed on the other. Much like an X-ray shows breaks in bones, the gamma rays reveal flaws or

breaks in welded joints.

a) Suggest a reason why alpha and beta would not be able to image metal joints. (2 marks)

b) Distinguish between the terms "gamma radioisotope" and "gamma ray". (2 marks)

c) The pellet material has a relatively long half life. Give two benefits of having a large half life

for use in gamma radiography. (2 marks)



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d) If the capsule was accidentally left sitting on the operator's thigh (approximately 6.00 kg)

which exposed the living tissue to the full amount of radiation, how long would it take for

the operator to be exposed to 200 mSv? (3 marks)

e) Consider now if the pellet inside the capsule was an alpha source and the capsule was left on

the operator’s leg for the same amount of time as calculated in part d. What would the

equivalent dose of the operator's leg be? (1 mark)

f) Residents of a recently built home were concerned that nuclear material had been used to

check the quality of the metal joints within the ceiling space. Make an argument as to

whether the concern of the residents is justified. (2 marks)



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There are a series of taut wires within the sounding board of a piano. Hitting the key of a piano

results a wire being struck; causing the wire to vibrate. The notes produced by a piano can be

analysed using the theory of standing waves within strings. The velocity of a wave along a wire is

affected by the tension and thickness of the wire. The higher the tension and the thinner the wire,

the faster the wave velocity.

a) In addition to the length of the wire, state two properties of a piano wire that determines

the frequency of the fundamental note it plays when struck. Justify your choice. (4 marks)

b) The length of the wires within the piano sounding board are usually similar in length.

Suggest a reason why adjusting the length of the wires to control the frequency is not

feasible. (1 mark)

keys

wires

sounding board



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c) The lowest note on a grand piano is 27.5 Hz. If the wire length is 0.700 m, calculate the

velocity of the wave along the wire. (3 marks)

d) On a particularly hot day, the piano can seem slightly out of tune (a key does not play the

correct frequency). Suggest two reasons for this and predict whether the note played on a

hot day is higher or lower than usual. (4 marks)



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The graph below shows the plot of binding energy per nucleon against the number of nucleons in

the nucleus. Use the graph to answer the following questions.

a) Define the term “binding energy per nucleon”. (2 marks)

b) Which nuclide is the most stable? Justify your choice. (2 marks)

c) Identify on the graph the section of the curve that represents the nuclides most likely to

undergo fission. Label this clearly. (1 mark)



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d) Predict the binding energy per nucleon of any isotope of tin. (1 mark)

e) Determine the binding energy of He-4. (2 marks)

f) He-4 can be produced by the fusion of two nuclei of H-2. Calculate the change in energy

during this fusion event in joules. (4 marks)



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Use the circuit diagram below to answer the following questions.

a) Calculate the equivalent resistance of the circuit, as seen by the emf source, when the

switch is open. (3 marks)

b) Calculate the power provided by the emf source, when the switch is open. (2 marks)

c) Calculate the potential difference across R1, when the switch is open. (1 mark)

R4

??

12.0 V

R1

120 Ω

R2

80.0 Ω

R3

60.0 Ω



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d) Calculate the potential difference across R2, when the switch is open. (1 mark)

e) Describe how the potential difference across R1 changes in response to the switch being

closed. Explain your choice; no numerical calculation is required but you should refer to

Ohm's law to assist with your explanation. (5 marks)



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Use the graph below to answer the following questions.

a) State the range of time(s) when the object had the following behaviours: (4 marks)

i. it had a constant velocity

ii. it was slowing down

iii. it was maintaining the highest speed achieved over the journey

-5

-3

-1

1

3

5

0 1 2 3 4 5 6 7 8 9 10

Vel

oci

ty (

ms-1

)

Time (s)

Velocity vs Time



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b) Determine the acceleration of the object during the first 2.00 seconds. (2 marks)

c) Determine the change in displacement of the object during the first 2.00 seconds. (2 marks)

d) Determine the change in displacement of the object that occurred between t=5.00 and

t=8.00 s (3 marks)



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Question 21 (continued)

e) Produce a graph of the acceleration of the object as a function of time for the full 10.0 s

onto the empty grid below. The velocity graph has been replicated for your convenience.

(4 marks)

End of Section 2

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Vel

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ms-1

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Time (s)

Velocity vs Time

-5

-3

-1

1

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0 1 2 3 4 5 6 7 8 9 10

Acc

eler

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n (

ms-2

)

Time (s)

Acceleration vs Time



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Section Three: Comprehension 20% (36 Marks)

This section has 2 questions. Answer both questions. Write your answers in the spaces provided.






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A voltage divider is a type of circuit that produces an output voltage (𝑉𝑜𝑢𝑡) that is some fraction of

the input voltage (𝑉𝑖𝑛). In its simplest form, a voltage divider is just a pair of resistors connected in

series. The input voltage is applied across the pair of resistors and the output voltage is taken across

just one of the resistors.

The voltage source is applied to an effective resistance equivalent to the combined resistance of the

pair of resistors. Thus, the current supplied by the voltage source (𝐼𝑇) is calculated from knowledge

of the input voltage and the resistance values; 𝐼𝑇 =𝑉𝑖𝑛

𝑅𝑇=

𝑉𝑖𝑛

𝑅1+𝑅2 (equation 1). By Kirchhoff's current

law the current through 𝑅2 is known and the output voltage can be calculated from 𝑉𝑜𝑢𝑡 = 𝐼𝑇𝑅2

(equation 2). By substituting equation 1 into equation 2:

𝑉𝑜𝑢𝑡 =𝑅2

𝑅1 + 𝑅2𝑉𝑖𝑛

Any circuit connected across the terminals of 𝑅2 will have the same voltage as the potential

difference across 𝑅2. Careful consideration of the values of 𝑅1 and 𝑅2 leads to the desired output

voltage of 𝑉𝑜𝑢𝑡.

A sensor based on a voltage divider can be used to measure a physical characteristic if that

characteristic can affect the resistance of 𝑅2. For example, the temperature of the surroundings of

𝑅1

𝑅2

𝑉𝑖𝑛

𝑉𝑜𝑢𝑡

𝑅1 and 𝑅2 are the pair of resistors

connected in series.

𝑉𝑖𝑛 is the emf applied to the circuit

𝑉𝑜𝑢𝑡 is the voltage measured across 𝑅2



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𝑅2 will influence the resistance of 𝑅2. This will result in 𝑉𝑜𝑢𝑡 also being affected and the

measurement of 𝑉𝑜𝑢𝑡 can be converted into a temperature reading.

Inside a multimeter is a potentiometer, the component responsible for measuring potential

difference. Potentiometers are only responsive over a small range of voltages. A voltage divider is

used to reduce the input voltage supplied to the multimeter down to a value that can be measured

by the potentiometer. For example, if the multimeter is set to measure in the 0-20 V range, a 20 V

input is first scaled down to 20 mV by a voltage divider which is a suitable range for a potentiometer.

a) State the purpose of a voltage divider. (2 marks)

b) Give two specific uses for a voltage divider. (2 marks)

c) In the passage, Kirchhoff's current law was stated as the proof of why the current in 𝑅2 can

be determined knowing the resistance values and input voltage. Elaborate on what

Kirchhoff’s current law is and how it was applied in this specific case. (2 marks)



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d) A voltage divider was constructed using two resistors; 360 Ω and 870 Ω. Calculate the

maximum and minimum output voltage of the divider when supplied with an 85.0 V input.

(3 marks)

e) Consider a voltage divider when used as part of a sensor circuit designed to measure

temperature. The surrounding environment increases in temperature, affecting resistor 𝑅2.

Describe how the output voltage of the sensor will change. (3 marks)

f) A voltage divider in a multimeter has a 1200 Ω resistor for 𝑅2. Determine the resistance of

𝑅1 which would allow the multimeter to convert a 20.0 V input to a voltage suitable for the

potentiometer. (4 marks)



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Question 22 (continued)

g) One criticism of voltage dividers is of the power they waste. By considering the physical

processes occurring at 𝑅1 while the voltage divider is in operation, suggest the basis for this

criticism. (2 marks)



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Fusion is the source of energy within the Sun and all stars. The high temperatures within stars causes

hydrogen to exist as ions, stripped of their electrons. Sometimes called the fourth state of matter,

collections of free ions are called plasma. Under normal conditions the positively charged nuclei

repel each other but if the conditions are right then the nuclei can overcome their electrostatic

repulsion, get extremely close and then fuse because of the attractive strong nuclear force. When

the nuclei of hydrogen fuse they lose mass and release energy.

A star’s gravitational force creates the right conditions for fusion to occur. On Earth, this is harder to

achieve. The same pressure as the interior of the Sun cannot be achieved on Earth and so the

hydrogen plasma must be heated to millions of degrees Celsius; ten times hotter than the Sun. The

goal of current research and prototype fusion reactors is to reach the ignition point, where enough

hydrogen fusion occurs within a small volume that the process is self-sustaining. The energy released

by the fusion will keep temperature and pressure levels high enough for more fusion to occur. With

extra fuel added over time this could lead to a clean and potentially unlimited source of energy.

The most likely fusion reactor to achieve success using modern technology is based on the fusion of

deuterium (D) and tritium (T), two isotopes of hydrogen. A single D-T fusion releases 17.6 MeV.

Fission of U-235 releases 200 MeV. At first glance, it may appear the fusion reaction is inferior but

there are a few clear benefits of using fusion over fission. Firstly, the energy released should also

take into consideration the mass of the fuel. A pair of hydrogen atoms has much less mass compared

to U-235 resulting D-T fusion producing just over four times more energy per unit of mass than

fission of U-235. Secondly, the ease of obtaining hydrogen to fuel fusion is much simpler than

obtaining U-235 for fission. Thirdly, and most importantly, is the comparison of the products

produced by each reaction. Fission of U-235 produces a range of heavy nuclei that are radioactive

and must be safely stored. D-T fusion produces helium which poses negligible health concerns and is

an inert gas. So why has fission been the primary form of nuclear based energy to date? Current

fusion reactor prototypes use more energy to create the fusion conditions that can be released by

the fusion reactions they contain. In comparison, fission occurs naturally without the need to create

high pressure and high temperature conditions; stick some U-235 fuel rods with a moderator

material in-between and the reaction will sustain itself.

The International Thermonuclear Experimental Reactor (ITER) group, a collaboration between 7

countries, are in the middle of the construction phase of a D-T reactor that will output 500 MW,

requiring 50 MW of input to establish and control the ignition of the plasma. The fusion chamber will

heat the plasma up to 150 million degrees Celsius and be strong enough to withstand a force equal

to twice the thrust required to launch a NASA Space Shuttle. First trials using D-T fusions within ITER

are expected to occur in 2035.

a) Describe what the plasma in a fusion reactor is. (1 mark)



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b) Explain why fusion is possible within the interior of a star but not under other conditions.

(3 marks)

c) Calculate the total mass lost, in kilograms, by the isotopes of hydrogen in a D-T fusion

reaction. (3 marks)

d) Describe a benefit that fusion has over fission. (2 marks)



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e) Explain why a moderator is required in a self-sustaining U-235 nuclear reactor, but not in a

self-sustaining fusion reactor. (4 marks)

f) How many times greater will the power output compared to power input be for ITER?

(1 mark)

g) Deuterium has a mass number of 2 and tritium has a mass number of 3. Using this data in

addition to information available in the passage, show that D-T fusion releases just more

than four times the energy per unit of mass compared to fission of U-235. (4 marks)

End of questions

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PHYSICS Unit 1 and 2

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Transcript of PHYSICS Unit 1 and 2