# Aqa a-level 24th May 2019 paper 2 physics unofficial mark schemeWatch

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Poll: Difficulty Level?
Hard asf (374)
19.89%
Meh (657)
34.95%
Easier than last year (506)
26.91%
Aced it/close to acing it (343)
18.24%
#1
Wzup guys I'll add questions/answers on here soon as I leave the exam! I'll update as you guys comment also so... commment the question(and q# if possible) and your answers
Evil Homer

1.1) Thermal physics - find spec.heat capacity [5 marks]
Work out the total energy, 12x890 I think = 10680J,
Work out energy to change state 2x10^5*0.05=10000J
Energy to increase temp = 10680-10000=680J
Work out SHC using Q=mc(deltatheta)
c=680/0.05*(77-70)=1900J/kgK (2sf)

1.2) is x(work done expanding) or y(work done to vaporise) bigger [4 marks]
Is X or Y greater? Calculating work done
X = difference in volume, then W = PV, (0.05/3.8-0.05/810)*1x10^6=1310J
Y = Q = ml = 0.05*2x105=10000J
so Y is greater

2.1) internal energy definition [2 marks]
sum of random distribution of potential and kinetic energies of molecules

2.2) explain absolute zero in terms of gas laws and 'kinetic law theory'(i think it meant KE theory) [2 marks]
At absolute zero, the kinetic energy of gas molecules is zero. And that gas laws show that at absolute zero, gases have no volume or pressure.

2.3) Find the rms speed [3 marks]
3/2kT = 310k i think?
then 1/2m(Crms)^2 = 3/2kT
4x10^-2/6.02x10^23=m
crms = 440 or smth

2.4) describe difference between kinetic energy of argon and helium at the same temp [1]
ke is same because temperature is the same

2.5) Explain why pressure exists in compressed gas [3 marks]
molecules collide
elastic collisions(KE conserved)
wall exerts force on molecules
molecules exert force on wall
f=delta mv/t so force applied on wall,
p=f/a so pressure exists

2.6) describe how you'd reduce pressure of same mixture of gases by changing 2 independent factors [2 marks]
reduce temperature -

lower ke as ke proportional to temperature
less frequent collisions/collisions per second decrease
less force
lower pressure

increase the volume -

molecules more spaced
collisons per second decrease
less force
hence lower pressure
3.1) calculate the potential of one sphere [3 marks]
23000V (i gott 12000 but apparently you use the capacitance)
3.2) suggest a solution to ONE problem when measuring d [2 marks]

use set square to reduce parallax

3.3) show that the electrostatic force between the spheres is 4x10^-3 [3 marks]
F=kQq/r^2 gave you 3.79x10^-3 roughly equal to 4x10^-3

3.4) angle was 7 degrees, explain whether this is consistent [2 marks]
Using components Tcostheta was the weight so you found T(0.03N i think)
Tsintheta was equal to the electrostatic force and finding theta from 0.03sintheta = 3.79x10^-3 gave you roughly 7 degrees

3.6) Deduce whether the gravitational force would have an effect on theta [2 marks]
got something like 1.6x10^-13, this is negligible compared to the electrostatic force hence no effect on angle

4.1) Define gravitational potential [2 marks]
the work done per unit mass, for a small point mass, to move that mass from infinity to that point

4.2) explain how the potential lines show the field is NOT uniform [1 mark]
distance between each line was different despite equal potential spacing

4.3) escape velocity [3 marks]
v=sqrt(2GM/R)
find M by subbing in values from diagram
gave smth like 2373 = 2400 ms-1 to 2sf

EMF coil question

5.1) find number of turns [3 marks]
number of turns was 120

5.2) find flux after rotating [2 marks]
1.3x10^-3

5.3) find max emf [1 mark]
using E=banw or whatever got some small value

5.3) Draw the flux linkage graph for the same time interval as the emf graph shown [1]
i got it as a cos wave? starting at max because at t=0 emf was 0

Nuclear question

6.1)Explain why the moderator needs to reduce KE of neutrons [1 mark]
To reduced the speed of them so they’re slow enough for fission as KE of neutrons is proportional to their speed

6.2) calculate the amount of energy in MeV left after 5 collisions [3 marks?]
2x10^6 x 0.37^5 = 1.39x10^4

6.3) Explain why the number of collision depends on the nucleon number of the moderator atoms [2 marks]
small nucleon number = less mass so speed of atom will be faster on collision so less collisions needed to lower KE, whereas a bigger mass means the atom would move more slowly so more collisions needed (smth along the lines of that)

6.4) calculation of energy released in MeV [3 marks?]
i think it was smth like 168 MeV not sure

6.5) 3 benefits of nuclear power [3 marks]
1. very large energy yield compared to other sources
2. doesnt produce toxic gases
3. easy to transport them to the reactor
any other valid reasons ngl

MCQ

8) brownian motion C
9)
10) Earth angular speed C
11)
12)
13)
14)
15)
16)
17)
18)
19)
20)
21)
22)
23)
24)
25)
26)
27)
28)
29)
30)
31)
32) what happens to KE and number of neutrons in the control rod C

CBBCDCABDCDDACCBBCCCABDBC but i think theres one missing there [quote badders_ ]

Last edited by mahmed69; 3 weeks ago
8
3 weeks ago
#2
1a) nuetron is absorbed by the coolant rod
1
#3
nice one lool
1a) nuetron is absorbed by the coolant rod
5
3 weeks ago
#4
9 mate
(Original post by xRealistTricks)
what time does your exam start
0
3 weeks ago
#5
tbf i was expecting you to go omg how did you get the paper please send it to me i will do anything
(Original post by mahmed69)
nice one lool
0
#6
one doesnt need the paper when one has the brains to actually do it
tbf i was expecting you to go omg how did you get the paper please send it to me i will do anything
1
3 weeks ago
#7
2
3 weeks ago
#8
Just collating answers I've seen on the main thread, not sure what question numbers these were.

SHC of liquid nitrogen:
Work out the total energy, 12x890 I think = 10680J,
Work out energy to change state 2x10^5*0.05=10000J
Energy to increase temp = 10680-10000=680J
Work out SHC using Q=mc(deltatheta)
c=680/0.05*(77-70)=1900J/kgK (2sf)

Is X or Y greater? Calculating work done
X = difference in volume, then W = PV, (0.05/3.8-0.05/810)*1x10^6=1310J
Y = Q = ml = 0.05*2x105=10000J
so Y is greater

Voltage on sphere:
Using V = Q/C, C = 4piE0r (as given in question) = 2.22x10^-12
V = 52x10^-9/2.22x10^-12=23379V = 23000V
3
#9
i got 12000 somehow not sure if ppl agree?
Just collating answers I've seen on the main thread, not sure what question numbers these were.

SHC of liquid nitrogen:
Work out the total energy, 12x890 I think = 10680J,
Work out energy to change state 2x10^5*0.05=10000J
Energy to increase temp = 10680-10000=680J
Work out SHC using Q=mc(deltatheta)
c=680/0.05*(77-70)=1900J/kgK (2sf)

Is X or Y greater? Calculating work done
X = difference in volume, then W = PV, (0.05/3.8-0.05/810)*1x10^6=1310J
Y = Q = ml = 0.05*2x105=10000J
so Y is greater

Voltage on sphere:
Using V = Q/C, C = 4piE0r (as given in question) = 2.22x10^-12
V = 52x10^-9/2.22x10^-12=23379V = 23000V
2
3 weeks ago
#10
Just collating answers I've seen on the main thread, not sure what question numbers these were.

SHC of liquid nitrogen:
Work out the total energy, 12x890 I think = 10680J,
Work out energy to change state 2x10^5*0.05=10000J
Energy to increase temp = 10680-10000=680J
Work out SHC using Q=mc(deltatheta)
c=680/0.05*(77-70)=1900J/kgK (2sf)

Is X or Y greater? Calculating work done
X = difference in volume, then W = PV, (0.05/3.8-0.05/810)*1x10^6=1310J
Y = Q = ml = 0.05*2x105=10000J
so Y is greater

Voltage on sphere:
Using V = Q/C, C = 4piE0r (as given in question) = 2.22x10^-12
V = 52x10^-9/2.22x10^-12=23379V = 23000V
0
3 weeks ago
#11
0
3 weeks ago
#12
0
3 weeks ago
#13
I would have got 12000V but is r the distance between the surface of both spheres or the distance between the centre of masses of both spheres
(Original post by mahmed69)
i got 12000 somehow not sure if ppl agree?
0
3 weeks ago
#14
Hate to say it but I disagree with 23000V. I think you used r as the radius of the sphere which is incorrect I believe
Just collating answers I've seen on the main thread, not sure what question numbers these were.

SHC of liquid nitrogen:
Work out the total energy, 12x890 I think = 10680J,
Work out energy to change state 2x10^5*0.05=10000J
Energy to increase temp = 10680-10000=680J
Work out SHC using Q=mc(deltatheta)
c=680/0.05*(77-70)=1900J/kgK (2sf)

Is X or Y greater? Calculating work done
X = difference in volume, then W = PV, (0.05/3.8-0.05/810)*1x10^6=1310J
Y = Q = ml = 0.05*2x105=10000J
so Y is greater

Voltage on sphere:
Using V = Q/C, C = 4piE0r (as given in question) = 2.22x10^-12
V = 52x10^-9/2.22x10^-12=23379V = 23000V
0
3 weeks ago
#15
Question 6c advantages to nuclear power
Answer: can generate a large amount of electricity and doesn’t produce greenhouse gases ... (3 marks)
0
3 weeks ago
#16
(Original post by mahmed69)
Wzup guys I'll add questions/answers on here soon as I leave the exam! I'll update as you guys comment also so... commment the question(and q# if possible) and your answers

1.1) Thermal physics - find spec.heat capacity [5 marks]
Work out the total energy, 12x890 I think = 10680J,
Work out energy to change state 2x10^5*0.05=10000J
Energy to increase temp = 10680-10000=680J
Work out SHC using Q=mc(deltatheta)
c=680/0.05*(77-70)=1900J/kgK (2sf)

1.2) is x(work done expanding) or y(work done to vaporise) bigger [4 marks]
Is X or Y greater? Calculating work done
X = difference in volume, then W = PV, (0.05/3.8-0.05/810)*1x10^6=1310J
Y = Q = ml = 0.05*2x105=10000J
so Y is greater

2.1) internal energy definition [2 marks]
sum of random distribution of potential and kinetic energies of molecules

2.2) explain absolute zero in terms of gas laws and 'kinetic law theory'(i think it meant KE theory) [2 marks]
cant remember what i wrote

3.1) calculate the potential of one sphere [3 marks]
12000V i think

3.2) suggest a solution to ONE problem when measuring d [2 marks]

3.3) show that the electrostatic force between the spheres is 4x10^-3 [3 marks]
F=kQq/r^2 gave you 3.79x10^-3 roughly equal to 4x10^-3

3.4) angle was 7 degrees, explain whether this is consistent [2 marks]
Using components Tcostheta was the weight so you found T(0.03N i think)
Tsintheta was equal to the electrostatic force and finding theta from 0.03sintheta = 3.79x10^-3 gave you roughly 7 degrees

3.5) Deduce whether the gravitational force would have an effect on theta [2 marks]
got something like 1.6x10^-13, this is negligible compared to the electrostatic force hence no effect on angle

EMF coil question

.1) find number of turns [3 marks]
number of turns was 120

.2) find flux after rotating [2 marks]
1.3x10^-3

.3) find max emf [1 mark]
using E=banw or whatever got some small value
max emf was 0.038V
Potential of sphere was 23000V
Solution for measuring D:
something to do with making D larger to reduce uncertainty?
1
3 weeks ago
#17
I’m not sure about ‘greenhouse gases’ as it does produce water vapour which is a greenhouse gas. Better to say no CO2.

Not sure if they’ll penalise though.
(Original post by grace frost)
Question 6c advantages to nuclear power
Answer: can generate a large amount of electricity and doesn’t produce greenhouse gases ... (3 marks)
0
3 weeks ago
#18
I also wrote that transport costs are cheap as only a small amount of fuel is required, and it preserves reserves of other fuel such as oil and coal.
(Original post by grace frost)
Question 6c advantages to nuclear power
Answer: can generate a large amount of electricity and doesn’t produce greenhouse gases ... (3 marks)
0
3 weeks ago
#19
Were you high taking this exam or something? SMH
1
3 weeks ago
#20
For multiple choice I got:
3
X

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