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# AQA AS Physics 7407/1 UnOfficial Markscheme 2018 watch

1. As suggested making an unofficial markscheme for Physics AS

Basis of answers by (Hari1241) but also added my stuff - If I missed anything or have any questions please feel free to ask...
Let's hope for a better paper 2!
Italics are where there is debate/uncertainty

1)Strong Interaction
Overcomes the electrostatic force of repulsion to keep them bound together
Attractive up to 3-4fm (3)
Repulsion below 0.5fm

2)Alpha-proton turn into neutron so mass number remains constant (show with AZx -> A-4Z-2Y+4,2 Alpha)
Beta-neutron turns into proton or other way and electrons are leptons so have no baryon number

3)UDS

4)Collaboration is neccesary to bring together experimental ideas, test them and reach new conclusions.

5)12.5ms-1/13ms-1 (2.s.f)

6)Acceleration is highest at the top, and the acceleration then decreases, reaching the same speed at A, then moving on a terminal velocity as there is no resultant force acting.

7)As rain falls into the truck, as it is vertical (and momentum is a vector quanitity) the momentum remains constant. Therefore as the mass increases the velocity must decrease (this is because some of the kinetic energy is used to 'speed up' the rain.
However very contriversial

8)A DIAGONAL set of ticks bottom left to top right.

Moment question:
Centre of mass has to be below A because if it was on either other side it would cause a moment and therefore not be in equilibrium.

Centre of mass = a point representing the mean position of the matter in a body or system

T1= ?? T2= ??

9) Volume question..

volume of iron 2.8*10^-8.

You did that by subtracting mass of ice cube with iron and without iron then using formula p=m/v

Can't remember other volume Q's?

10)C causes electron emission, work it out, B doesn't therefore A cannot either as A has lower energy

11)LONG AF velocity question
1)Work out work fuction using Work function/h=fmin
2)convert to Joules
3)work out photon energy
4)Ek Mx=hf-work function

Unsure of 12-14
12)Electricity AC lowest resistances 6 ohms 3 ohms AC BD respectively.

13)no clue with E

14)Current increases with a decrease in resistance work it out to get 2A for initial current and 2.5A for final current.

15) Bright fringes, with with black fringes in between. The central maximum has higher intensity and then as you go out the fringes show the light spectra, from blue to red.

16)W=LAMBDAD/S Show how an increase in wavelength leads to an increase in the fringe spacing providing others remain constant.
Red diffracts more, larger wavelength, farther apart outer side of the fringes
Green less, smaller than red, so it is on the inner fringe.
They superpose every 5wl's of red, and every 6 of green, causing a bright maxima.

17) 6 MARKER,

As s is inversely proportional to w, as you decrease s, w increases. As s is a small value the percentage uncertainty rise is much greater therefore has more of an affect that the lower percentage uncertainty given by w.
W is proportional to D, so as D decreases so does W, therefore both cause a larger percentage uncertainty, so reading for wavelength has a higher uncertainty.

Question on the extension/youngs mod is missing (any more?)
Extension I got 253m or something, although didnt seem realistic as it was only a 12m thing... Potentially 0.01m?
2. I know I'm missing stuff so any other questions you know (even if you dont know the answer) please do let me know!
3. (Original post by TomasD)
I know I'm missing stuff so any other questions you know (even if you dont know the answer) please do let me know!
i got like 3.9x10^something negative for the extension i think. It was a small extension though.
4. (Original post by RickHendricks)
i got like 3.9x10^something negative for the extension i think. It was a small extension though.
Would make a lot more sense than mine It was just the
Young Modulus = FL/A(delta)L right?
5. (Original post by TomasD)
Would make a lot more sense than mine It was just the
Young Modulus = FL/A(delta)L right?
yeahhh

i got massive first, like in 3000000 or something, then realized i did something wrong, in which I got a tiny answer.

if u used the formula, but got wrong answer, u should get around 2 marks
6. There is no colour separation with the double slit I made that mistake
7. For extension I got 0.01m, seemed reasonable
8. (Original post by RickHendricks)
yeahhh

i got massive first, like in 3000000 or something, then realized i did something wrong, in which I got a tiny answer.

if u used the formula, but got wrong answer, u should get around 2 marks
Thats what I did!! Rearranged for YoungsModulus x A / FL = ^L

Um Youngs modulus was somethingx10^11? Diameter 5x10-2? Force was 12000 and L was 12? Unless im not remembering correct idk but It just didnt work for me
9. (Original post by ppkpojoij)
There is no colour separation with the double slit I made that mistake
Isn't there? As it's with white light I thought that as the different colours have different wave lengths they arrive at the second fringe and constructively interfere at different points? Or is this me going crazy?
10. (Original post by TomasD)
Thats what I did!! Rearranged for YoungsModulus x A / FL = ^L

Um Youngs modulus was somethingx10^11? Diameter 5x10-2? Force was 12000 and L was 12? Unless im not remembering correct idk but It just didnt work for me
btw, central maxima for the fringe is white colour, since black.
11. (Original post by TomasD)
Thats what I did!! Rearranged for YoungsModulus x A / FL = ^L

Um Youngs modulus was somethingx10^11? Diameter 5x10-2? Force was 12000 and L was 12? Unless im not remembering correct idk but It just didnt work for me
they gave the cross sectional area not diamter
12. Nah you’re right I think. Although I didn’t put that 😂 forgot so much
13. (Original post by TomasD)
Isn't there? As it's with white light I thought that as the different colours have different wave lengths they arrive at the second fringe and constructively interfere at different points? Or is this me going crazy?
I put this too, but the first slit makes the waves coherent
14. Any one know the answer for falling rain?
15. Momentum Q;
The truck doesn’t move exactly vertically downwards, and the addition of rain makes the truck heavier so it’s momentum increases. For the rain, as the truck is not moving exactly vertically downwards, the momentum of the rain changes as the direction of its velocity changes
16. (Original post by SP0409)
Momentum Q;
The truck doesn’t move exactly vertically downwards, and the addition of rain makes the truck heavier so it’s momentum increases. For the rain, as the truck is not moving exactly vertically downwards, the momentum of the rain changes as the direction of its velocity changes
just search in the internet it says : no change in momentum because momentum is a vector but truck would slow down because its mass increases.
17. (Original post by PPun)
just search in the internet it says : no change in momentum because momentum is a vector but truck would slow down because its mass increases.
That's what i've been saying
18. (Original post by ppkpojoij)
I put this too, but the first slit makes the waves coherent
I know that (was really hoping it would be a question 'why is there a single slit' but there wasnt)
Although when it passes through 2 slits, one has to travel further than the other - and as in white light you have light of all different wave lengths, the blue light (small wl) will be at a maxima before red, creating that spectrum as you move away from the centre?
19. (Original post by TomasD)
I know that (was really hoping it would be a question 'why is there a single slit' but there wasnt)
Although when it passes through 2 slits, one has to travel further than the other - and as in white light you have light of all different wave lengths, the blue light (small wl) will be at a maxima before red, creating that spectrum as you move away from the centre?
I hope you're right obv cos then I'd be right too, but I don't think so.
I mentioned that because blue has a shorter wavelength it is difftracted less and so the fringes are tinged with blue, and the red diffracts more due to longer wavelength as you said. It seems you are confusing path difference as in distances travelled with fringe colour?
20. So basically the momentum question is conservation of momentum?

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