# AQA A Level Physics PAPER 3 3rd june 2019 Unofficial Mark scheme

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#1
Evil Homer

We all know that was clapped so let’s get on with the task

1.1 Precautions when using source of radiation [2 marks]
Handle with tongs facing away from you
Keep sealed in lead-shielded container when not in use to limit exposure
Keep at arms distance (minimum) at all times
point downwards when it use

1.2 determine how many ways A goes to K [1 mark]
5

1.3 determine how many paths A and M lie in the path of decay of Ra to Pb [3 marks]
15 i think (didnt clock this was bloody 3 marks negl there was 1 goddamn line for working)

1.4 Diagram with aluminium graph on opposite page find minimum thickess, [2 marks]
got 11mm from graph but Beta would travel through 11mm so to stop it i put 12mm
Water measuring question

1.5 y+e = sqrtk/sqrtA [5 marks]
make in y = mx+c
find gradient, sub a pair of coordinates from the graph
k = smth big like 1.8x10^5 mm2Bq

1.6 find e [2 marks]
y intercept using similar triangles i got -29...smth

2.1 Percentage uncertainty given d % and L% and gradient ie Q/h was 6.4% [2 marks]
i remember being confused about the n rearranging
19.8%

2.2 units of the weird N symbol [1 marks]
Second box I think Nm-2s

2.3 method of measuring Q, including reduction of uncertainties [4 marks]
use measuring cylinder start stop clock for 1 minute measure volume of water in cyclinder, Q=volume/60
uncertainty reduction: time for longer period, reduces % uncertainty in T as well as Measurement of q because q would also be greater, use a more graduated cylinder

2.4 deadass graph question show decay constant is 4.5x10^-3(even tho it said show it still gave answer space?) [2 marks]
spent a full 7 minutes on this question, tried finding half life then saw the next questions wanted the half life wtf
then did smth with the intercepts and gradient etc then subbed into another equation that got me 4.49x10^-3

2.5 find half life [1 mark]
ln2 / decay constant = 154 seconds
possible ecf for this from part Q2.4

2.6 how to make sure tube was vertical [1 mark]
the CLASSICAL set square-ruler combo

2.7 tube is now angled at 30degrees draw the graph [2 marks]
no clue here i did smth times sin(30) n drew a more steeper line although this is probably wrong

3.1 vernier caliper diameter of rod [1 mark]
0.71mm

3.2 how you'd reduce random error in result of diameter[2 marks]
measure at different points along rod take average exclude anomalies blah blah
reduces random error

Random questions from memory
find frequency from graph [2 marks]
63Hz using the time base from graph (8 small divisions = 1.6cm = 0.016s time period)

find wavelength of wire across bridge [2 marks]
got 57.8cm then doubled to get 1.16m

speed of wave from the data we calculated [1 mark]
c = 70 m s^-1 (or 71 m s^-1)

find mu [3 marks]
use harmonics formula f=1/2Lsqrt(t/mu)
mu = 9.9*10^-4 kg m^-1

find density of the object final question [3 marks]
mu = 9.9*10^-4 kg m^-1
Diameter = 0.71 mm
Density: rho = 8.9*10^3 kg m^-3
Last edited by mahmed69; 2 years ago
12
2 years ago
#2
8
2 years ago
#3
Density question?
0
2 years ago
#4
Section A:
1. Precautionsandle with tongs facing away from you, Keep sealed when not in use to limit exposure
2. I skipped this but it gave a graph and asked to calculate minimum thickness of aluminium
3. Routes (I got 11 but guessed) and also what nuclei were formed between the nuclei given and the last nucleus it decayed

For section B:

One question was to showed that the data followed hubbles law

Last question about what makes distance to quasars difficult to measure, I talked about their being black holes at te centre?
Last edited by urgurlbecca; 2 years ago
3
2 years ago
#5
I remember calculating a frequency in the region of 600 something? I think?
6
2 years ago
#6
There was also a units quesioj i ticked the second box too
Last edited by urgurlbecca; 2 years ago
0
2 years ago
#7
got 4 for the routes it could only go in certain directions anyway
2
2 years ago
#8
(Original post by DivockOrigi27)
I got 15
1
2 years ago
#9

(Original post by DivockOrigi27)
12
2 years ago
#10
I got 6
9
2 years ago
#11
I got 12 for the possible number of routes of decay and I got A,B,i for the common letters for decay
2
2 years ago
#12
I think 2.1 was 19.8
(Original post by mahmed69)
Evil Homer

We all know that was clapped so let’s get on with the task

1.1 Precautions when using source of radiation

1.2 determine how many ways A goes to K

1.3 determine how many paths A and M lie in the path of decay of Ra to Pb

1.4 Diagram with aluminium graph on opposite page find minimum thickess,
got 11mm from graph but Beta would travel through 11mm so to stop it i put 12mm
Water measuring question
2.1 Percentage uncertainty given d % and L% and gradient ie Q/h was 6.4%

2.2 units of the weird N symbol
Second box I think Nm-2s
5
2 years ago
#13
How to measure flow rate+reduce uncertainity:
Measure time using a precise digital stopclock
Measure volume of water given off in beaker with small graduations
Repeat trials and take average volume at each time(?)

Can I just say I found section a really hard wtf
0
2 years ago
#14
8100
(Original post by usaamayate)
Density question?
1
2 years ago
#15
For those who didn't do the Turning Points optional unit, the answer to the multiple choice SI unit question for viscosity was the second one. (They gave it to us in our optional unit).
3
2 years ago
#16
I got 5
(Original post by nyxnko_)
got 4 for the routes it could only go in certain directions anyway
2
2 years ago
#17
I got 8700
8100
0
2 years ago
#18
Anyone else get these?

5 routes
A, B, I (felt very decision-mathsy, did that one!)
k = 1.9*10^5 Bq mm^2
e = 30 mm

lambda = 4.50*10^-3 s^-1
T_1/2 = 154 s
Unit: N m^-2 s
Percentage uncertainty: 19.8 %

EDIT: Just changed the unit; had originally said N m^2 s^-1.

f = 61 Hz (from time period of 16.4 ms)
d = 57.8 cm, giving lambda = 1.16 m
c = 70 m s^-1 (or 71 m s^-1)
mu = 9.9*10^-4 kg m^-1
Diameter = 0.71 mm
Density: rho = 8.9*10^3 kg m^-3

Obviously not everyone will have done Astrophysics, so I'll put those in another post.
Last edited by mupsman2312; 2 years ago
9
2 years ago
#19
(Original post by urgurlbecca)
I remember calculating a frequency in the region of 600 something? I think?
I got 61 Hz. POT error by one of us, possibly?
0
2 years ago
#20
I agree with A, B, I, but I got 5 for the number of routes. Did you consider that alpha and beta decay can only go in one direction on the diagram (i.e. downwards)?
(Original post by Naolek)
I got 12 for the possible number of routes of decay and I got A,B,i for the common letters for decay
0
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