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# AQA Physics P3 higher tier Unofficial Markscheme

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1. (Original post by surina16)
1.5 = 1/sinC
sinC = 0.666...
C=42(2sf)
Whaaaaaaatt!!! ðŸ˜ ðŸ˜ i am just sooo stupid i forgot to do inverse sin ðŸ˜¢ðŸ˜¢ love maths sooooo much but with physics...... I forget that there is maths so i leave my maths brain at homeðŸ˜’
2. (Original post by Mahrez)
No it was 1.1 nm
Would you care to explain how you got that answer?
3. (Original post by Akila1)
Would you care to explain how you got that answer?
Yeah if you give me the numbers
4. Can someone explain to me how you got 400m/s in the ultrasound question?
Also was the question about calculating the critical angle to two significant fingers or two decimal places?
5. i got to 500m/s on the speed of ultrasound..
6. (Original post by greenapple10)
i got to 500m/s on the speed of ultrasound..
I got 1600m/s. I don't know if it is actually right, but I did something like this:

The ultrasound travelled 4cm twice over as it went from the skin to the baby and back to the skin/transducer, which is 8cm = 0.08m.

The time taken for this was 80 microseconds - 30 microseconds, which is 50 microseconds.

Speed is distance/time = 0.08m/50x10^-6s = 1600m/s

Is this right though???
7. I got 1600 m/s for ultrasound questionn and explained earlier in the thread how.

I can't remember seeing a question about describing the image? I did PH3HP, would someone assure me that this wasn't on this paper? Also, could someon explain how they got the answer for the moments to be 0.9. I got 0.48 as you can't add the distances together, I did:

1.5 Ã— 0.20 + 1.5 Ã— 0.12 = 0.48 Nm and so the force was 0.48 on chain??
8. (Original post by BDunlop)
I got 1600 m/s for ultrasound questionn and explained earlier in the thread how.

I can't remember seeing a question about describing the image? I did PH3HP, would someone assure me that this wasn't on this paper? Also, could someon explain how they got the answer for the moments to be 0.9. I got 0.48 as you can't add the distances together, I did:

1.5 Ã— 0.20 + 1.5 Ã— 0.12 = 0.48 Nm and so the force was 0.48 on chain??
I am also wondering about this question. As the pedal was apparently stationary I assumed the moment of the chain on the pedal and foot on the pedal were equal (as they acted in opposite directions?) so did F1 x D1 = F2 x D2. I can't actually remember what I got as the force but it may have been 0.9N. I don't have a clue if it is right though! Sorry if this is completely wrong. Hopefully it is correct but what you did seems good....
9. (Original post by Bulbasaur10)
I am also wondering about this question. As the pedal was apparently stationary I assumed the moment of the chain on the pedal and foot on the pedal were equal (as they acted in opposite directions?) so did F1 x D1 = F2 x D2. I can't actually remember what I got as the force but it may have been 0.9N. I don't have a clue if it is right though! Sorry if this is completely wrong. Hopefully it is correct but what you did seems good....
I'm talking about the same question yeah, but what I couldn't see is that f1 Ã—d1 can't have equalled f2 Ã— d2 because the perpendicular distance was that much greater so how could it have been stationary? And also, the chains moment would of had to act downwards because there was nothing substantial pushing it upwards, as the foot pushing down would have caused the chain to be pulled down?
10. There was a question about like light intensity and why the same light wave changed I think it was 2 marks, it had route A and B what was the answer?

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11. (Original post by BDunlop)
I'm talking about the same question yeah, but what I couldn't see is that f1 Ã—d1 can't have equalled f2 Ã— d2 because the perpendicular distance was that much greater so how could it have been stationary? And also, the chains moment would of had to act downwards because there was nothing substantial pushing it upwards, as the foot pushing down would have caused the chain to be pulled down?
I don't really know, but didn't the diagram show the chain moving up? ðŸ˜‚ðŸ˜°ðŸ˜– I didn't really see how it could have either but I could have sworn there was an upward arrow along the chain on the diagram..... ðŸ˜€

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12. (Original post by blueribbons99)
There was a question about like light intensity and why the same light wave changed I think it was 2 marks, it had route A and B what was the answer?
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Good point, route a I think it was was entering the optical tube at such an angle that it did not refract on the boundary (parrallel to it) however Ray b was totally internally reflected and so it took a longer route, meaning that this light ray took longer to reach the end of the fibre hence why the intensity increased then decreased rather than immediately being there
13. (Original post by Bulbasaur10)
I don't really know, but didn't the diagram show the chain moving up? ðŸ˜‚ðŸ˜°ðŸ˜– I didn't really see how it could have either but I could have sworn there was an upward arrow along the chain on the diagram..... ðŸ˜€

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Yea there was an upward arrow it confused the f*ck out of me ngl. But still, if there was a downward force acting on the pedal and that was the only pivot then there's no way that there could have been both an upward force and a downward force? Surely? They really screwed with my head
14. (Original post by BDunlop)
Yea there was an upward arrow it confused the f*ck out of me ngl. But still, if there was a downward force acting on the pedal and that was the only pivot then there's no way that there could have been both an upward force and a downward force? Surely? They really screwed with my head
Yeah it was so confusing! I think the grade boundaries will be low so if anything happens it will be fine though! I assumed the force of the chain acted around the same pivot as the foot but it was an odd diagram so who knows...

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15. There was nothing on Flemings left hand rule
Please READ THE TITLE OF THE DISCUSSION before commenting on something not included in the paper and giving me a literal mini heart attack.
Kind regards.

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16. (Original post by vault111)
There was nothing on Flemings left hand rule
Please READ THE TITLE OF THE DISCUSSION before commenting on something not included in the paper and giving me a literal mini heart attack.
Kind regards.

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Which paper did you sit? there was one question asking which direction the force from the motor effect would be- it was downwards
17. (Original post by BDunlop)
Which paper did you sit? there was one question asking which direction the force from the motor effect would be- it was downwards
There are two slightly different papers. Some people sat, like me, PH3HP, and other schools did further additional unit 3. It sounds weird but they are always slightly different.

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18. (Original post by Bulbasaur10)
There are two slightly different papers. Some people sat, like me, PH3HP, and other schools did further additional unit 3. It sounds weird but they are always slightly different.

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Me too, I sat PH3HP
19. (Original post by barney.jones123)
So I can get an A?!
Usually about 70% for an A anyway. You should be fine. However I'm no expert
20. (Original post by brotherteresa256)
Right, that exam was awfully hard... Let's make a mark scheme guys. Please put in any questions or answers you can, preferably with question number if you can remember it. I'll try to keep updating it as best I can, but i'm only human

ALSO, THIS MARK SCHEME IS VERY INCOMPLETE, SO DON'T EXPECT IT TO BE 100% CORRECT

1.
a) Why was electromagnet better for sorting rubbish? (1 mark)
Because it can be switched on and of/activated and deactivated OR it is more powerful than a normal magnet
b) How can the students use this equipment to create an electromagnet, and test it - and vary its strength? (6 marks)
Wrap Insulated wire around nail. Suspend in the wooden clamp. Attach to power supply with connectors. put paperclips under and increase power until paperclip is attracted OR set to certain power and lower until paperclip is attracted. Then repeat with different height/power.

Calculation: 0.08m or 0.04m divided by 110x10^-6 or 50x10^-6, We're not sure yet (but I think the answer is 400 m/s) (3 mark)
Why is X-rays not used with unborn babies?: X-ray causes ionisation which are damaging to the foetus' cells, causing them to become mutant and divide uncontrollably. This leads to cancer. (3 marks)
How does an X-ray work question: X-rays emitted toward a photographic CCD. Hard tissue like bone absorbs the rays, making them white on the image, but softer tissue allows them to pass through (3 mark)
Question on wavelength: Shorter (1 mark)

3 - Stability Questions
What is meant by the 'centre of mass'?: the point where the mass appears to be concentrated (1 mark)
Why is tower B more unstable than A?: narrower base, higher centre of mass (2 mark)
Why doesn't this tower fall over?: The line of action of the weight lies within the base so there is no resultant moment causing it to topple (2 mark)

4 - Foot peddle and drums/Moments questions
What is meant by moment of the force: A DICTIONARY DEFINITION: "A measure of the turning effect produced by a force about an axis.The magnitude of the moment is the product of the force and the perpendicular distance from the axis to the line of action of the force" (1 mark)
1.5 N force from toe. 0.20m from pivot to the chain. 0.12m from pivot to toe: 0.9N??? (3 marks)
Graph showing different lengths of drum hinges compared to volume of sound produces at different forces (3, 6, 9 newtons) (2 mark)

5 - Eye correction/lenses/Ray trace diagram questions
Critical angle (2 significant figures): 1/1.5 = 0.6666.. sin^-1(0.6666..) = 42 degrees (3 mark)
(image was formed behind object, magnified, and was virtual because the lines on the other side of the lens did not converge)??? (3 mark)
Reason for long longness: Lens in eye too weak OR eyeball too short (1 mark)
Source of energy for cutting cornea: LASER (1 mark)
(Not too sure, but there was an M/N object question) (3 mark)
C/B lens question: draw the lens fatter??? (1 mark)

Grade boundaries are looking low too. from a purely personal viewpoint (don't take these 100% seriously) these are what i think the boundaries will be:

A* - 40
A - 34
B - 28
C - 23
D - 17
E - 12

(P.S. Below are some mark schemes for the P2 exam you wonderful physicists might want)
http://www.thestudentroom.co.uk/show....php?t=4171131
http://www.thestudentroom.co.uk/show....php?t=4171228
http://www.thestudentroom.co.uk/show....php?t=4171902 --- This one is probably the best, well done to lily628 for making it

Just to clarify here this isn't all the questions is it? As that only adds up yo 40, and you are saying u reckon we need 49 for an a* lol

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