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UNOFFICIAL MARKSCHEME!~AQA GCSE Physics Unit 2 25th Janurary NEW SPEC

Poll

How did you find the exam?

Please everyone asking me about grade boundaries: I don't know! Im not an examiner! Your guess is as good as mine; perhaps ask a teacher if you want to know. Thanks

Unofficial Markscheme below, credit to isaac, + input from mrkingpenguin himself :wink:

1) Forces:
a) What was the force that attracted the droplets of oil to the ground?
• Weight or (MAYBE accept) gravity
b) What does the fact that the oil droplets are hitting the ground at greater distances apart tell us about the state of the lorry (assuming the drops are falling every 5 seconds)
• The lorry is accelerating, this is because time is a constant, so velocity must be directly proportional to distance between drops, as distance increases, so must velocity. As this happens multiple times the vehicle is accelerating. Mention formula. (1)
c) Other than poor brakes, what else affects breaking distance?
• Weather conditions, road surface, velocity
d)what causes the forces?
-Mass of car/aerodynamic profile of car?
d) An object is pushed with a force of 3kN, 25m, calculate the work done?
• 3 000 x 25 = 75000J (unit not given)
e) This graph shows current vs voltage of a diode, what is the activation current
• 0.02 - 0.025A

2) Radioactivity:
a) The graph shows an element… what is the half life
• 3.8h
b) How many protons + how many neutrons does an alpha particle have?
• 2p and 2n
c) Rn^222 .86 --> A^4 .2 + Po^? .?
• ^218 .84
d) Name one MAN MADE SOURCE of background radiation?
Aeroplanes, nuclear bombs/ accidents, medical things, granite houses etc.

e) A teacher used a geiger counter to measure the ratiation, why did the results vary?
• Readings different because of different conditions/ cosmic radiation from the sun varies/nuclear decay is random (anwer wanted)

f) Why can the scientists not make a conclusion from this data?
• Lots of other factors affect background radiation eg.areoplane trips, hospital visits dose so no accurate conclusions can be made. Data suggests trend as opposed to proofs.

3) Stars:
a) What is meant by a stable star?
• A star is stable when the force created by fusion is equal to the force due to gravity, thus the star has reached equilibria, as the star no longer expands/ collapses.
b) What is the relationship between mass of star and duration of main sequence (using table)?
• The bigger the star's mass, the smaller the main sequence.
d) Explain the life cycle of a star grater than our sun after main sequence?
• 6 marks QTC:
My summary:

As a star enters its main sequence, it starts to fuse hydrogen to release energy. Once the hydrogen supply runs out, the star begin to collapse inwards due to gravity. The collapse inwards increases the density of the star, thus providing more heat + pressure - just enough for the fusion of helium to begin. The heat produced by fusion of helium, like hydrogen, powers the process of fusion until the point where the fuel (helium) runs out. At this stage, if the star is large enough (our sun is not), fusion of carbon will begin and the process will continue, the fusion of carbon providing sufficient energy to expand + become a red giant, (and can continue until all the carbon has fused to become iron). At this stage, once again the star will collapse inwards, the extra pressure will cause a supernova to be born, an explosion which releases all the fused element to space. At this point, if the mass is high enough, it will become a black hole, if not, a neutron star.

Alternative answer provided by Dalek1099:

The star becomes a red super giant as the outwards force of heat, produced through nuclear fusion is larger than the inwards force of gravity, forcing the nuclei to fuse, as larger nuclei are made.Eventually, when the hydrogen fuel completely runs out because of the large force of heat being removed the star collapses quickly under its own gravity in a supernova releasing elements heavier than iron produced during its lifetime.The star now is a neutron star, made up only of neutrons and in even heavier stars the gravitational collapse is so large that the star becomes a phenomena known as a black hole, which is small and dense and has a large gravitational force that nothing can escape including light because the escape velocity from a black hole is higher than the speed of light.

c) How fast does fusion compare in larger stars, compared with smaller stars?
• Nuclear fusion reactions last longer in larger stars because their main sequence is shorter thus their nuclear reactions must be faster.
d) Why can't scientists predict when a star will die?
• It takes millions of years for hydrogen to run out so its impossible to predict it to the exact year/ we can't calculate the exact amount of hydrogen fuel in the star and other conditions can change the time it takes for fuel to run out by a few years. This is because the stars are physically distant from ourselves so necessary experiements cannot be carried out. (1)

4) Electronics:
a) Draw a diode(boxA) and variable resistor(boxB)
• you'll have to look these up as this is written in ascii
b) Name the 2 mistakes in this circuit
• ammeter should be connected in series, voltmeter should be connected in parallel, NO mark for switch I dont think
c) Work out the resistance of the diode?
• 0.3v / 0.008A = 37.5ohms
d) What is the frequency on this oscilloscope?
• 1/(0.01 x 4) = 25Hz (unit given)
e) Why does the diode change the shape on the oscilloscope?
• allows current to flow only one direction so the current can't flow in the negative direction.

5) Velocity/ Time graphs:
a) How does the change in go-cart shape affect it's terminal velocity?
• reduces air resistance due to better aerodynamic profile, less negative force from particles; resultant force at same speed positive; so Y continues to accelerate
b) What is the acceleration of this car on the graph?
• (7.5m/s - 0m/s) / 3s = 1.7 m/s/s [1.66/1.6r]
c) What is the distance traveled form point J to K?
• 2.5m/s x 35 = 7.5m alt: ½ x 5 x 35 = 7.5m

6) Mains electricity:
a) Here is a thermister, heat is provided, what effect does this have?
• resistance decreases + current increases.
b) What's one advantage of an RCCB?
• quick; sensitive; can be re-used;
c) What does the RCCB do when the wire breaks?
• the RCCB compares the current of the live and neutral wires, if they are too different, the circuit breaks in 0.06 seconds or less.
d) Calculate the charge of this appliance at 230v, 11A, for 2 hours?
• 11A x 2 x 60 x 60 = 79200 coulombs (unit not given)
e) What is the frequency of the mains power supply?
• 50Hz
f) Calculate the energy transferred by this device in 2 hours?
• 79200C x 230V = 18216000J

Feel free to discuss this upcoming exam or ask any questions :smile:

(edited 11 years ago)

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Reply 1

Mrkingpenguin

Also please read exam rules before posting

Reply 2

ali_d123

I have this too. Jesus the mock was hard. I have nearly finished watchign all of mygcsescience p2 videos!

Reply 3

hannapoole

I found the mock so hard too, and I also missed out on so many marks for not writing specific words, feel like this exams going to be terrible!

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Reply 4

syhash

Any ideas about the 6 mark question? :smile:

Reply 5

Efemena15

Original post by syhash

Any ideas about the 6 mark question? :smile:

The 6 mark from the mock?

Reply 6

syhash

Original post by Efemena15

The 6 mark from the mock?

I actually meant to ask for any predictions for the 6 marker coming up on next week's exam, but I did the P2 exam last summer, I meant to post this on the chemistry thread, sorry!

Reply 7

sakbo

Doing this exam, got full ums in the last one. really want the same on friday :smile:

Reply 8

sakbo

How long per day do you guys revise? I just wondering...

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Reply 9

sakbo

Quick question : if the exam question asks for one reason can you just list many reasons that you know to be safe? Or do they just take the first one?

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Reply 10

Quantaˌ

Original post by sakbo

Quick question : if the exam question asks for one reason can you just list many reasons that you know to be safe? Or do they just take the first one?

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Posted from TSR Mobile

I think that you will lose the mark if the reason is too vague or one of the reasons is wrong. This is to stop students from guessing and using a 'shotgun' approach- giving multiple answers to have a greater chance of being right.

Reply 11

syhash

Original post by sakbo

Quick question : if the exam question asks for one reason can you just list many reasons that you know to be safe? Or do they just take the first one?

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Posted from TSR Mobile

I'm not 100% sure, but I think as long as you include one point from the mark scheme, you can still get a mark. You might not get full marks if the question is more than 1 or 2, but if you're really not sure about the answer it's better to write something than leave it blank! :smile:

Reply 12

Pings

Original post by sakbo

Quick question : if the exam question asks for one reason can you just list many reasons that you know to be safe? Or do they just take the first one?

I think I read somewhere that they'll only take the first one, because it specifically says 'list one...'

Reply 13

syhash

Original post by sakbo

Quick question : if the exam question asks for one reason can you just list many reasons that you know to be safe? Or do they just take the first one?

Original post by Quantaˌ

Just found this in a mark scheme for January 2012:
'Marking of lists - This applies to questions requiring a set number of responses, but for which students have provided extra responses. The general principle to be followed in such a situation is that ‘right + wrong = wrong’.
Each error/contradiction negates each correct response. So, if the number of error/contradictions equals or exceeds the number of marks available for the question, no marks can be awarded.'

Reply 14

username1042290

Haven't found this unit too hard, but my way of revising has always been to do a lot of past papers as I keep focused that way: with only the specimen and 1 previous paper for P2 this is hard - any suggestions of how I could revise? I find copying out a revision guide just makes me more and more demotivated.

Reply 15

pinkgorilla

the life cycle of stars is annoying me... and i used to like stars :/

Reply 16

Ammy97

I'm doing this exam, feeling very nervous as I really want a good grade haha

This was posted from The Student Room's iPhone/iPad App

Reply 17

clara16

Original post by Jackwtaylor

Have exactly the same problem! The mygcsescience videos have helped me so much, and there's sometimes questions on the end of them. If not i've been going through old spec papers trying to find related questions & the CGP physics workbook (p1 p2 & p3 together) have been ok i guess.

My teacher sent us 160 pages of exam styles questions that they make up in school end of topic tests with so you could ask your teacher for something similar?

Reply 18

username1042290

Original post by clara16

Thanks for the help, we got a booklet type thing today which I'm going to go through tonight, I've certainly not done as much revision as I'd hoped this past week with snow disruption etc. so will try to get down to it tonight!