Doing section 1 tomorrow, should go fine. What are the control variables for yours? I can only think of using polystyrene cups and same volume of water?

Reply 989

ThatGirlx

Original post by lolface32

Oh cool

Doing section 1 tomorrow, should go fine. What are the control variables for yours? I can only think of using polystyrene cups and same volume of water?

Oh okay my bad not the same thing lol!
Good luck on yours :smile:

!

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

Reply 990

HennersPD

Original post by Mrkingpenguin

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:

When was this posted? Was it before the exam? :smile:

just wondering because its so good!

Reply 991

ThatGirlx

Original post by HennersPD

When was this posted? Was it before the exam? :smile:

just wondering because its so good!

Obviously after the exam...

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

Reply 992

Davothebigafro

What do you lot think the ums' will be for the ISA's?

Reply 993

Captain Anonymous

A* will probably around 38-41 and A will be around 35-38 100 UMS will be around 46

Reply 994

HennersPD

Original post by ThatGirlx

Obviously after the exam...

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

Not necessarily as when I saw it the day after our exam, It said it was posted "one week ago" meaning it was posted BEFORE the exam, probably around the 18th Jan , which is breaking the rules and regulations set up by AQA.

Reply 995

Mrkingpenguin

Original post by HennersPD

1. how an earth would i have early access to an exam paper
2. If you checked on my recent posts you would see that i posted it afterwards
3. The exam wasant even 1 week ago
4. Has it occurred that I may have EDITED the post
5. If it really was posted early do you really think it would still be up...-_-
6. I compiled the markscheme with two other user, we are all fairly competent physicists who can also use textbooks....

Intelligence is lacking in some users...

Reply 996

Captain Anonymous

It is a bit strange to see it posted a week ago from the day the exam was sat.... Just saying :L

Reply 997

bbadonde2

Original post by Raasib21

It is a bit strange to see it posted a week ago from the day the exam was sat.... Just saying :L

I was on the thread while the answers were posted and it was around 8 pm in the night. mrkingpenguin collected the answers from other users contributions.

Reply 998

Kill3er

Original post by Dalek1099

46 and 48 should be 100 UMS but they could mark them down -my science teacher said that they were marked down by quite a bit but I got 47 so I was safe for 100 UMS.

How does that work?
Do AQA check a few, and if they are marked too generously then they reduce ALL the students marks in the school by x amount?
Or do they recheck all of them?

Reply 999

Dalek1099

Original post by Kill3er

How does that work?
Do AQA check a few, and if they are marked too generously then they reduce ALL the students marks in the school by x amount?
Or do they recheck all of them?

As far as I know, some samples are sent to AQA, they mark them and generally they see trends and can simply mark everyone elses up or down but if there is no trend or consistency then they ask for more or all of the coursework pieces.This is the system as I know it and it seems ridiculous because if a teacher marks too slack for coursework this means it can be impossible for students to get top marks, especially at A-Level ISA's were the boundaries between grades can be so tiny- the system is unfair and AQA should have to mark them all.