Unofficial AQA Physics Unit 3 GCSE NEW SPEC Mark Scheme

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Quantaˌ
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Starting the unofficial physics unit 3 mark scheme. This is for the AQA GCSE New Specification test which everyone did on the 23th May 2013.

Can everyone submit the answers they can remember to this thread? I'll add them to this post when we've got a few.


________________________________ ________________________________ ________________________________

Here is the mark scheme:

Question 1 [10]

  1. .
    Image [2]
  2. Iris [1] May allow Pupil
    Ciliary muscles changes shape (width) of eye lens [1]
    Eye lens focuses light onto the retina [1]
  3. As age increases, near point increases (near point is further away from eye): at 10 years near point was 10cm while at 40 years it was 25cm. [2]
  4. A larger sample size could be used (more than 4 people) and mean near points could be worked out. [1]
  5. Power= 1/Focal Length= 1/(40cm/100)= 1/0.4m= 2.5 Diopters [2]


Question 2 [8]
  1. Design A is more stable as it has a wider base and lower centre of mass. [2]
  2. Ray diagram of 3 rays with arrows showing direction [4]
  3. The camera image can be described as real and inverted. [2] Allow diminished


Question 3 [9]
  1. Ultrasound is above the human hearing range which is 20Hz to 20000Hz. Therefore, ultrasound is beyond 20000 Hz. They are non-ionising but are partially reflected at the boundary of tissues of two different densities. The reflected waves are detected by the transmitter and a computer builds an image. They can be used to detect different tissues but are not useful in producing an image of bone. Meanwhile, X-rays waves are high frequency and have a short wavelength. They are also ionising, having no safe limit. This can cause cell mutation and lead to cancer. They are absorbed by dense materials, such as bone, but pass through tissues. X-rays expose a film or CCD to produce an image. Bones are white as these areas are not exposed. This allows fractures to be seen clearly. [6]
  2. X-rays are ionising and could harm the unborn child by causing cell mutation leading to cancerous growths. [2]
  3. One medical use of ultrasound is to destroy kidney stones. [1]


Question 4 [5]
  1. The property that all liquids are virtually incompressible. [1]

    OR

    The property of all liquids are that pressure acts equally in all directions. [1]
    .
  2. Force exerted by master piston is 84N. Must show working out and correct use of following formula: Pressure (N/m2)= Force (N) x Area (m) [2]
  3. Force F of the master piston is smaller than the force exerted by the slave pistons since hydraulic systems are force multipliers. [2] Allow use of data


Question 5 [12]
  1. Centripetal force [1]
    The force is towards the centre of the G-machine. [1] Allow towards the centre of the circle of motion
  2. As speed increases, size of the force on the astronaut increases. [1]
    As radius of the G-machine decreases, size of the force on the astronaut increases. [1]
    Deceasing the radius of the G-machine has more effect on the force than increasing the speed [1]
  3. The change of force between 20m/s to 40m/s is: 40m/s-20m/s= 16000N-4000N= 12000N [1]
  4. The current through the wire creates a magnetic field which interacts or repels the magnetic field of the permanent magnets. Therefore, a force is applied on the wire.
  5. Side A: Force is ↓
    Side C: Force is ↑ [1]
  6. Side B experiences no force as the wire is parallel to the magnetic field lines of the permanent magnets. [1]
  7. The operators change increase the strength of the permanent magnets. [1] Allow increase number of turns in coil or increase current in wire
  8. Yes, space exploration produces many technological advancements that can be used elsewhere. [1]

    OR

    No, space exploration is a waste of money that could be used in areas that directly benefit humans such as healthcare and medicine. [1]

    Allow acceptable reasons to justify choice


Question 6 [7]
  1. Moment= Force x Distance → Force= (Moment/Distance)= (36Nm/0.6m)= 60N [2]
  2. The bag topples as there is a resultant clockwise moment- the resultant moment is not zero. This is due to the line of action of the weight being outside the base of the bag. [2]
  3. Frequency= 1/Time Period = 1/(160 secs/10 swings)= 1/16= 0.0625Hz [3]


Question 7 [9]
  1. The alternating current in the first coil produces an alternating or changing magnetic field. This magnetic field is increased by the iron core. The second coil cuts magnetic field lines as the magnetic field changes. This induces an alternating potential difference. If the circuit is complete, an alternating current will flow through the second coil. [3]
  2. Potential difference the charger supplies to the laptop is 20 V. Must show working out and correct use of following formula: (Primary Potential Difference/Secondary Potential Difference) = (Primary Turns in Coil/Secondary Turns in Coil) [2]
  3. Current in the primary coil is 0.3 A Must show working out and correct use of following formula: Primary Current (Amps) x Primary Potential Difference (Volts) = Secondary Current (Amps) x Secondary Potential Difference (Volts0 [2]
  4. Another advantage of a switch-mode transformer is that it can be used with high frequencies (50000Hz to 200000Hz). [1]

    OR

    Another advantage of a switch-mode transformer is that it wastes little energy when not in use. [1]
    .
  5. An advantage of these batteries is that they would have a longer life and, so, would not need to be replaced as often which would be useful in areas where replacement batteries are not readily available. [1]


OR
[*]An advantage of these batteries is that they would have a longer life and, so, would not need to be replaced as often which would lead to less batteries would be thrown away into landfills which cause environmental and ecological damage.

________________________________ ________________________________ ________________________________

Here are the unofficial grade boundaries:

A* : 49
A : 40
B : 31
C : 22
D : 13


These are subject to change...
3
holly12345
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Kill3er has already kindly typed them out for us!

1) Diagram of eye (2 marks)
1b) Complete table (3 marks)
1c) Near point. What can you conclude from the data (2 marks)
1d) Suggest how data obtained could be improved (1 marks)
1e) Focal length = 40cm calculate power of lens (2 marks)

2) Compare stability of two rafts (2 marks)
2b) Complete ray diagram (4 marks)
2c) Two words to describe nature of image produced by the lens in the camera (2 marks)

3*) Describe the features of ultrasound and x-rays, and what happens when each type of wave entres the human body (6 marks)
3b) Explain why its not safe to use x-rays to produce image of an unborn child (2 marks)
3c) Give one use of ultrasound for medical treatment (1 marks)

4a) What property of liquid enables a hydraulic brake system to work? (1 marks)
4b) Calculate force exerted on the liquid by the master piston? (2 marks)
4c) How does the size of this force compare to force f made by the master piston?...
Give a reason for your answer... (2 marks)

5) G-Machine question.
Name of force...
Direction of force... (2 marks)
5b) State 3 conclusions that can be made from the graph (3 marks)
The speed of G-machine 1 is increased form 20m/s to 40m/s
Change in force? (1 marks)
5c) Explain why side A experiences a force (2 marks)
Draw arrows of the force acting on A and C (1 marks)
When horizontal, side b experiences no force...why? (1 marks)
5d) What can the operators do to make the G-machine rotate faster? (1 marks)
5e) Do you think we should spend money on space exploration? Yes or No? (1 marks)

6) Calculate the upwards force the man applies to the handle of his bag? (2 marks)
6b) When the man lets go of the bag handle, the bag falls and hits the floor. Why? (2 marks)
6c) Pendulum makes 10 complete swings every 160 seconds. Frequency + Unit) (3 marks)

7a) The alternating current flowing through the primary coil of the transformer creates an alternating current in the secondary coil? Why? (3 marks)
7b) Potential difference the charger supplies to the laptop? (2 marks)
Calculate the current in the primary coil? (2 marks)
7c) Give one other advantage of the switch mode transformer? (1 marks)
7d) Suggest one advantage of developing these batteries?
4
SportsFan
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#3
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1) Diagram of eye (2 marks)
-Cornea
-Retina
1b) Complete table (3 marks)
-Iris/Pupil
-Ciliary muscle changes shape of lens,
1c) Near point. What can you conclude from the data (2 marks)
-The older you get the more your near point increased
-Data proof
1d) Suggest how data obtained could be improved (1 marks)
-Larger sample size as she only use 4 people
1e) Focal length = 40cm calculate power of lens (2 marks)
2.5 D
2) Compare stability of two rafts (2 marks)
Raft A:
-Lower Centre Of Mass
-Wider Base
2b) Complete ray diagram (4 marks)
-Draw diagram properly
-Real Rays
-Draw the object as inverted, real & diminished
-Draw arrows

2c) Two words to describe nature of image produced by the lens in the camera (2 marks)

3*) Describe the features of ultrasound and x-rays, and what happens when each type of wave entres the human body (6 marks)
3b) Explain why its not safe to use x-rays to produce image of an unborn child (2 marks)
3c) Give one use of ultrasound for medical treatment (1 marks)

4a) What property of liquid enables a hydraulic brake system to work? (1 marks)
4b) Calculate force exerted on the liquid by the master piston? (2 marks)
4c) How does the size of this force compare to force f made by the master piston?...
Give a reason for your answer... (2 marks)

5) G-Machine question.
Name of force...
Direction of force... (2 marks)
5b) State 3 conclusions that can be made from the graph (3 marks)
The speed of G-machine 1 is increased form 20m/s to 40m/s
Change in force? (1 marks)
5c) Explain why side A experiences a force (2 marks)
Draw arrows of the force acting on A and C (1 marks)
When horizontal, side b experiences no force...why? (1 marks)
5d) What can the operators do to make the G-machine rotate faster? (1 marks)
5e) Do you think we should spend money on space exploration? Yes or No? (1 marks)

6) Calculate the upwards force the man applies to the handle of his bag? (2 marks)
6b) When the man lets go of the bag handle, the bag falls and hits the floor. Why? (2 marks)
6c) Pendulum makes 10 complete swings every 160 seconds. Frequency + Unit) (3 marks)

7a) The alternating current flowing through the primary coil of the transformer creates an alternating current in the secondary coil? Why? (3 marks)
7b) Potential difference the charger supplies to the laptop? (2 marks)
Calculate the current in the primary coil? (2 marks)
7c) Give one other advantage of the switch mode transformer? (1 marks)
7d) Suggest one advantage of developing these batteries?
2
Manchester2497
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4a) What property of liquid enables a hydraulic brake system to work?
it cannot be compressed(1 marks)
4b) Calculate force exerted on the liquid by the master piston?
think it was 84N (2 marks)
4c) How does the size of this force compare to force f made by the master piston?... the force f exerted on the master piston is smaller than the force exerted on the slave pistons
Give a reason for your answer... because the slave pistons have a larger cross-sectional area (2 marks)
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forzajanie
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#5
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These are the answers which I put.......

2c) real, diminished, inverted (any 2)

3)* Ultra sound beyond human hearing range so more than 20000 Hz. When ultra sound reaches a boundary between two different media it gets partially reflected. However some waves get transmitted through the boundary and get refracted. X-rays waves are high in frequency and have a short wavelength. They are passed through healthy tissues and get absorbed by bones. X-ray waves cause ionization meaning they damage healthy cells and cause cancer. (This was for 6 marks)

3b) X-rays cause mutations, therefore cause abnormalities in growth of the unborn child.
3c) breaking up kidney stones

4a) Liquid is in compressible so the force gets transmitted in all directions.
4b) 84 Pa
4c) Force f is larger because the liquid is a force multiplier and increases the force.

5a) Centripetal force
towards the center
5d) Increase the current to make the g-machine make faster

6a) 36Nm/0.6m=60N (the forcE)
6b) The bag falls down because the line of action is outside the base of the bag so there will be a resultant force causing the bag to fall down.
6c) Time period+ 16s
so frequency = 1/16=0.0625 Hz (must state units!)

7b) 20 volts
7c) 0.03 amps


By the way for the pendulum question i wrote 0.06 instead of 0.0625 because i thought 0.0625 was too long but in my working out it does say 0.0625 so will i get the full 3 marks??
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forzajanie
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What do you think the grade boundaries will be?
I thinkk...

49-60 A*
48-42 A
But I dont know
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Saywhatyoumean
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I have a feeling they'll be around
65 for an A*?
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Heskey123
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#8
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(Original post by Saywhatyoumean)
I have a feeling they'll be around
65 for an A*?
The paper is out of 60............
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Quantaˌ
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#9
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I'll be working this soon with other members. We'll be using a poll like last time to assess the paper's difficulty.
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Captain Anonymous
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#10
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I've got around 47 raw marks, roughly what grade/UMS
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holliemay
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#11
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(Original post by Captain Anonymous)
I've got around 47 raw marks, roughly what grade/UMS
Ditto! Hoping this will be at least 77 ums as that's what I need for an A*
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Captain Anonymous
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its likely to be an hig A, low A*
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Randomer96
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#13
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Cheers for this, basically got full marks apart from the 12000N question and will I get the marks for saying the force was towards the centre of the cylindor? For 5.
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Randomer96
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#14
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Oh yeah and it's Pupil not Iris. The CGP workbook has a question with a table the same, and the answer book said Pupil.
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Quantaˌ
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#15
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(Original post by Randomer96)
Oh yeah and it's Pupil not Iris. The CGP workbook has a question with a table the same, and the answer book said Pupil.
But from the question, I felt it was asking for iris. I've put allow both answers but I'm not sure about this...
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Randomer96
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#16
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(Original post by Quantaˌ)
But from the question, I felt it was asking for iris. I've put allow both answers but I'm not sure about this...
Can you remember the exact wording? I asked my dad cos he's an optician and he said the iris make the pupil bigger or smaller, while the pupil actually lets light in.
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Helena...
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#17
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For q4.3 wasn't it that the force is greater
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ellipsis...
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#18
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#18
I thought that the force in 5a is gravity, not centripetal force??

*i wrote gravity not friction
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Quantaˌ
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#19
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(Original post by ellipsis...)
I thought that the force in 5a is friction, not centripetal force??
No, I'm pretty sure it was centripetal force...
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ahmed15
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#20
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Guys u know the question about putting in the arrows for the direction for the force, are u sure it wasn't the other way round


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