2015 physics units 1 2 paper marking guide PDF

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2016 Physics Year 11 ATAR Semester 2 2016 Solutions...

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 

The papers may only be reproduced within the purchasing school according to the advertised conditions of sale. Test papers must be withdrawn after use and stored securely in the school until Friday 4th December 2015.

PHYSICS UNITS 1 & 2 2015

Name: _______________________________________________________ Circle your teacher’s name: Holyoake Lyle Patterson

Shashikumar

Faulkner

Smith

Time allowed for this paper Reading time before commencing work: Working time for paper:

ten minutes 2.5 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 Standard items: pens (blue/black preferred), pencils (including coloured), sharpener, correction fluid/tape, eraser, ruler, highlighters Special items:

up to three non-programmable calculators approved for use in the WACE examinations, drawing templates, drawing compass and a protractor

Important note to candidates No other items may be taken into the examination room. It is your responsibility to ensure that you do not have any unauthorised notes or other items of a non-personal nature in the examination room. If you have any unauthorised material with you, hand it to the supervisor before reading any further.

Physics Units 1 & 2 2015

2

Structure of this paper

Section

Section One: Short response Section Two: Problemsolving Section Three: Comprehension

Number of questions to be answered

Suggested working time (minutes)

Marks available

9

9

42

40

27

7

7

75

79

53

2

2

33

31

20

150

100

Number of questions available

Total

Percentage of exam

Instructions to candidates 1.

The rules for the conduct of Western Australian external examinations are detailed in the Year 12 Information Handbook 2015. Sitting this examination implies that you agree to abide by these rules.

2.

Write your answers in this Question/Answer Booklet.

3.

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.

3.

You must be careful to confine your responses to the specific questions asked and to follow any instructions that are specific to a particular question.

5.

Spare pages are included at the end of this booklet. They can be used for planning your responses and/or as additional space if required to continue an answer. ● Planning: If you use the spare pages for planning, indicate this clearly at the top of the page. ● Continuing an answer: If you need to use the space to continue an answer, indicate in the original answer space where the answer is continued, i.e. give the page number. Fill in the number of the question that you are continuing to answer at the top of the page.

6.

The Formulae and Data booklet is not to be handed in with your Question/Answer Booklet. © WATP

Section One: Short response

27% (40 Marks)

This section has 9 questions. Answer all questions. 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. Spare pages are included at the end of this booklet. They can be used for planning your responses and/or as additional space if required to continue an answer. ● ●

Planning: If you use the spare pages for planning, indicate this clearly at the top of the page. Continuing an answer: If you need to use the space to continue an answer, indicate in the original answer space where the answer is continued, i.e. give the page number. Fill in the number of the question that you are continuing to answer at the top of the page.

Suggested working time: 42 minutes. Question 1

(4 marks)

State which of the three types of nuclear radiation (, , ), that result from natural radioactive decay, best matches each of the following properties. the radiation that is most ionising



the radiation consisting of particles of least mass the radiation that is emitted at the lowest speed the radiation that is not deflected by an electric field



or

γ

 

Question 2 (5 marks) Electricians must replace fuses with residual current devices (RCD) when they do some work on houses in Western Australia. a)

Explain how RCDs protect people from electrocution.

(2 marks)

If there is an imbalance of current flowing into and out of the house of more than a predetermined amount (1 mark) the RCD breaks the circuit in a very short time (1 mark)

b)

Even with RCDs protecting all circuits in a house can people, using electricity still be electrocuted in that house? Explain. Can they be electrocuted?

____Yes____

Explain.

(1 mark) (2 marks)

If a person touches both wires (active & neutral) and becomes part of circuit (1 mark) and no current flows to Earth (1 mark)

Question 3

(5 marks)

The diagram below shows a sound wave moving through air at 25 C. The sinusoidal graph above the sound wave indicates the variation in air pressure as the wave travels. 6.24 m Pressure Variation

SOUND WAVE

(a)

(b)

Calculate the value of each of the following quantities for this sound wave. Wavelength:

1.56 m

Frequency:

222 Hz

(346 m/s / 1.56 m)

(1 mark)

Period:

4.51 x 10-3 s

( 1/222 Hz)

(1 mark)

(6.24 m / 4 whole wave cycles)

(1 mark)

On the pressure variation graph above, superimpose a sinusoidal graph to show the variation in particle displacement as the wave travels through the air. (2 marks) 1 mark same wavelength 1 mark phase difference of 90°

Question 4 a)

(6 marks)

A violin string is 0.65 m in length. Sketch the standing waves produced for the 1st and 2nd harmonics and determine their wavelengths. (3 marks)

1st

Sketch

Wavelength = 1.3 m

2nd

Sketch

Wavelength = 0.65 m

1 mark for each sketch, 1 mark if both wavelengths

b)

If the wave speed in the string is 4.00 x 102 m s-1, calculate the frequencies of the first two harmonics? (3 marks)

f=

c λ

1st

f=

1 mark 400 =308 Hz 1.3

2nd f = 2 x 308 = 615 Hz

1 mark 1 mark

Question 5 (4 marks) A student heated 337 g of nickel in a Bunsen burner flame until it reached a temperature of 534 °C. She then placed the nickel into 1.59 L of water at a temperature of 21.0 0C. The final temperature of the nickel and water mixture was 32.3 C when thermal equilibrium was reached. a)

Calculate the energy that transferred out of the nickel into the water. (2 marks)

Q = m c ΔT = 1.59 x 4180 x 11.3 Q = 7.51 x 104 J

b)

1 mark 1 mark

Calculate the specific heat of the nickel.

Q = m c ΔT

c=

Q m ΔT

=

(2 marks)

7.51 x 104 0.337 x 501.7

1 mark

ΔT=(534- 32.3) = 501.7 0C c = 444 J kg-1 K-1

1 mark

Question 6

(3 marks)

A sample of thigh bone from a recently deceased dog was tested and found to have an activity of 0.360 Bq. A similar size sample was obtained from a sabre tooth tiger thigh bone uncovered at an archaeological site and its activity was measured. Over a one day period a reading of 7.776 x 103 counts was registered on a Geiger counter for the archaeological sample. The half-life of radioactive carbon is approximately 5730 years. (a)

Determine the activity (becquerels) for the archaeological sample.

(1 mark)

A=

N t

1 mark

(b)

Determine the age of the thigh bone from the archaeological site.

=

7776 24 x 3600

= 9.00 x 10-2 Bq

0.360→0.180→0.09 N N0

=

1 ( ) 2

n

.09 .36

2 half lives 2 x5730 = 11500 years =

2 x 5730 = 11 500 years

1 4

=(

1 2 ) 2

2 half lives

(2 marks)

or 1 mark 1 mark

Question 7

(2 marks)

Write a balanced nuclear equation for the following decay: Barium 141 ( 141 56

Ba

→

0 −1

e

+

141 56

Ba ) by beta negative decay.

141 57

La +

νe

2 marks

No marks deducted for not having mentioned ν e (2 marks) Question 8

(5 marks)

A model rocket has a mass at launch of 1.5 kg (of which 60% is fuel). (a)

On the diagram at right, sketch and label the two forces acting on the rocket as it lifts off at launch. (1 mark)

(b)

If the initial acceleration of the rocket is 15 ms -2, calculate the thrust force of its engine at launch. (2 marks) thru st

Fw = 1.5 x 9.8 = 14.7 N Fnet = ma Fnet = W + T✔

Ft 

Ft - Fw = ma

or

Ft - 14.7 N = 1.5 kg x 15 m/s 2 Hence Ft = 14.7 N + 22.5 N = 37.2 N✔ Fnet = Ft - Fw

or

ma = Ft - mg

Ft = ma + mg = m(a+g) = 1.5( 15+9.80) = 37.2N) ✔ weigh t (c)

The acceleration of the rocket increases as it flies higher and higher. Suggest why this would happen. (2 marks)

As the rocket flies higher it burns its fuel, and so loses mass and weight.

F

✔



Hence the acceleration a = Fnet/m will increase as mass m steadily decreases while net force Fnet increases steadily due to the steady decrease in weight. ✔



No marks for variation of ‘g’ with height

Question 9

(6 marks) -7

a)

Blue light has a wavelength of 4.75 x 10 m in air. Calculate its frequency in this medium. (2 mark)

f=

f=

b)

c λ x 108 m s-1 3.00 x 10 8 −7 4.75 x 10

c= 3.00 1 mark = 6.32 x 1014 Hz

If the blue light travels at 2.00 x 10 8 m s-1 in glass, calculate its frequency and wavelength in glass. (3 marks)

f = 6.32 x 1014 Hz c= 3.00 x 108 m s-1 c= 2.00 x 108 m s-1 λ=

2 3

c)

1 mark

1 mark λ = 4.75 x 10-7 λ=?

x 4.75 x 10-7 = 3.17 x 10-7 m

1 mark 1 mark

Blue light travels from air into a glass block at an angle of incidence of 30 0. Complete the diagram showing what happens at the surface. (Calculations NOT necessary.) (1 marks)

No marks deducted if reflected ray not shown

Section Two: Problem-solving

53% (79 Marks)

This section has seven (7) questions. Answer all questions. Write your answers in the spaces provided. Spare pages are included at the end of this booklet. They can be used for planning your responses and/or as additional space if required to continue an answer. ● ●

Planning: If you use the spare pages for planning, indicate this clearly at the top of the page. Continuing an answer: If you need to use the space to continue an answer, indicate in the original answer space where the answer is continued, i.e. give the page number. Fill in the number of the question that you are continuing to answer at the top of the page.

Suggested working time: 75 minutes.

Question 10

(13 marks)

Bernard Tomic celebrates a victory by climbing into the crowd and smashing a tennis ball vertically upwards. The ball is hit from a position 2.75 m above the ground with an initial velocity of 55.1 m s -1 upwards. The ball has a mass of 57.3 g. a)

Calculate the time the ball takes to reach the ground.

(3 marks)

up is +ve

s = ut + 0.5 at2 -2.75 = 55.1 t -4.9 t2 t = 1.13 x 101 s

or v = u+at 0=55.1-9.8 xt t =5.62 sec Distance travelled v2 = u2 + 2as s= 154.8m Total distance = 157.7m

s = ut + 0.5 at2 t=5.67 sec Total time = 5.62 +5.67 = 11.3s b)

Calculate the velocity of the ball after 5.10 s.

t = 5.10 s v = u + at = 55.1 – 9.8 x 5.1 v = 5.12 m s-1 up

c)

Calculate the distance that the ball travels to reach the ground.

Highest point v = 0 v2 = u2 + 2as 0 = 55.12 -19.6 s 2 s = 1.55 x 10 m Total distance = (2 x 1.55 x 102) + (2.75) = 3.13 x 102 m

d)

Calculate the mechanical energy of the ball whilst in flight.

EM = EK + EP = 0.5 mv2 + mgh = 0.5 x 0.0573x 55.1 2 + 0.0573 x 9.8 x 2.75 = 8.85 x 101 J

e)

(2 marks)

1 mark 1 mark

(3 marks)

1 mark 1 mark 1 mark

(3 marks)

1 mark 1 mark 1 mark

The tennis racquet is in contact with the ball for 0.312 s. Calculate the impulsive force on the ball. (2 marks)

F = (mv – mu)/t = 0.0573 (55.1 -0)/0.312 F = 1.01 x 101 N

1 mark 1 mark

Question 11 (12 marks) A group of Physics students wanted to measure the speed of sound in air using two methods. The air temperature is 25 0C. I) For the first method they had the following equipment available to them: Stop watch, starting pistol, a dark wall on the edge of an oval, a tape measure II)

For the second method they had the following equipment available to them: A 4.80 x 102 Hz tuning fork, large measuring cylinder, ruler, water, lengths of round tubes that fitted inside the measuring cylinder.

a)

(i)

Design an experiment to determine the speed of sound using all the equipment in the first list. (3 marks)



(Dark wall back drop so can see smoke from starter’s pistol)



Tape measure out (100 m) from pistol and Observer @( 100 m)



Stop watch time from seeing smoke & then hearing sound.



Calculate using s/t Any three - 1 mark for each

(ii)

Create one set of data for this experiment and show how the speed of sound can be calculated using that data. (2 marks)

s = 100 m t = 0.289 s 

1 mark

consistent values to arrive at 346 m s -1

c = s/t = 100/0.289 c = 346 m s-1

1 mark if 346 as T = 25 0C

b)

(i)

Design an experiment to determine the speed of sound using all the equipment in the second list. (4 marks)

Nearly full measuring cylinder with water, place round tube in water

1 mark

Place vibrating tuning fork over tube & find 1 st resonant point

1 mark

Measure with ruler Repeat to find 2nd resonant point

1 mark

Calculate 2 x (R2 – R1) x 480 = c

1 mark

(ii)

Create one set of data for this experiment and show how the speed of sound can be calculated using that data. (3 marks)

R1 = 0.172 m R2 = 0.532 m R2 – R1 = 0.532 – 0.172 = 0.360 m c = 2 x 0.360 x 480 = 346 m s-1

1 mark 1 mark 1 mark

Question 12

(14 marks)

Some liquid alcohol of mass 1.30 g was placed in a sealed glass container and vaporised at 70 ºC. The container with the vapour was placed in a large water bath that was kept at room temperature. The change in temperature of the alcohol was recorded every two minutes. There was constant rate of energy output from the alcohol such that a total of 2330 J of energy was transferred out in a 50 minute time period. Assume that heat loss to the surroundings was negligible. Room temperature was 26 0C. Temp (0C) 70 64 59 53 48 42 42 a)

Time (minutes ) 0 2 4 6 8 10 12

Temp (0C) 42 42 42 42 42 42 42

Time (minutes ) 14 16 18 20 22 24 26

Temp (0C)

Draw a graph of the data in the table.

42 42 42 42 41 39 37

Time (minutes ) 28 30 32 34 36 38 40

Temp (0C) 35 33 31 29 27 26 26

Time (minutes ) 42 44 46 48 50 52 54 (5 marks)

A spare grid is at the end of the paper (page 36) in case you need to redo your graph.



1 mark for each labelled axis with units 2 for accuracy 1 for line of best fit

b)

Use the graph to compare (qualitatively) the specific heat capacity of the liquid alcohol with that of its vapour? (Explain your reasoning) (3 marks)

Steepness of slope Steeper slope = Lower specific heat ‘c’

1 mark 1 mark

(Specific heat capacity of a liquid is defined as the amount of heat required to raise the temperature of a unit mass of liquid by 1 ◦ C) cliquid = 3 x cvapour 1 mark cliquid > cvapour

c)

What state/s of matter is/are present in the container between fifteen and twenty five minutes? (2 mark)

gas/liquid

d)

(right or wrong)

2 marks

Determine the latent heat of vaporisation of the alcohol. Time = (34-10) = 24 minutes Q = 2330 x 24/50 = 1.12 x 103 J Lv = Q/m = 1.12 x 103/1.3 x 10 -3 = 8.60 x 105 J kg-1

e)

(2 marks) 1 mark 1 mark

In terms of energy, explain why the temperature of the substance did not decrease while energy transferred from it to the water between fifteen and thirty minutes. (2 marks)

Temp did not decrease no change in EK

(Any 2 - 1 mark each)

Particle got closer together decrease in E P Energy given out during condensation = energy released to the water

Question 13

(10 marks)

A 12.0 V battery is connected to a circuit with four resistors as shown in the diagram below. A current of 0.95 A flows through the 12  resistor.

I R

12.0 V

0.95 A

12

A

B 22

15

(a)

Calculate the potential difference (voltage) between points A and B. (2 marks)

Voltage between A and B = voltage across 12  resistor (in parallel) V = I R = (0.95 A) x (12 )

(b)

= 11.4 V

✔

✔

Find the current flowing through the 15  resistor.

Current through 15  resistor = current flowing between A and B I = V / R = (11.4 V) / (15  + 22 )

= 0.308 A ✔

(2 marks)

✔

Determine the rate at which heat is being produced in the 22  resistor. (2 marks)

(c)

P = I2 R

✔

=...