AQA Physics PHYA5 - Thursday 18th June 2015 [Exam Discussion Thread]

Indeed. Good luck

My answers for the questions that didn't have a "show that the answer is this" were:

Thermal and Nuclear
Range of $\alpha$ = 0.1m
Range of $\beta$ = 2.0m
Density = $1.63 \times 10^{17} kg m^{-3}$
Number of nuclei = $2.35 \times 10^{17}$
Energy used = 47000J
$\left(C_{rms}\right)^{2} = 2.07 \times 10^{7} m^{2} s^{-2}$
Temperature = 319K

Astrophysics
Maximum distance = $5.36 \times 10^{11} m$
Diameter = 15m (unsure about this)
In the 6 mark essay my period was 4 days, and my velocity was 109800 ms-1
Magnitude = -0.01 (definitely derped on this; 1sf and I missed the minus lmao)
Temperature = 16100K
White dwarf radius = $9.37 \times 10^{6} m$
Black hole radius = $2.95 \times 10^{13} m$
Age of the universe = $4.96 \times 10^{17} s$

But the neutron number changes so wouldn't the nucleon number be bigger or smaller so the size of the nucleus should be different.

So shouldn't the dispersion be different?

I think you are confusing scattering with diffraction. It is true that in diffraction mass would make a difference as the radius would change but with scattering of two charged particles only the charge will make a difference.

What was the density question? I did (51*1.67*10^-27)/(4/3 *pi*r^3) but I can't remember what r was.

Also, going off of the past grade boundary trends, A* will be 57 and full UMS will be 62

Was it 1.4x1017? I think r was about 5fm...

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Anyone who did Medical Physics, quote me, how did you find the paper?

But for alphas hitting the nucleus, and being deflected back on themselves surely the size of the nucleus matters?

Yeah, 5fm or so - think I got 1.6 or 1.4 *10^-17

How did you guys do the number of Neptunium nuclei? N=N_0e^(-lambda*t)?

Yeah there was, the exam code was PHYA5R

more difficult indeed, slightly odd question. Rest of it was fine thankfully

That 6 marker, kill me please. Everything else was pretty standard though.

Under the assumption of equally distributed charge the electrostatic force on the alpha particle will not change even for an increase in radius of the gold nuclei due to an increase in mass. The charge density of the nucleus will change but the strength of the field produced by it will not. Ergo the scattering effect will remain the same.

Hey i did the medical paper! I found it alright, except the ear question! How did you find it?

Yes, I thought it was a nice paper! But same here, that graph question on the ear was tricky. I wasn't a fan of the last question on the fluoroscopic image intensifier either as I hadn't revised it.

how did you write in nuclear eqn?