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# AQA Physics PHYA4 - 20th June 2016 [Exam Discussion Thread] Watch

1. (Original post by james2mid)
No
(Original post by james2mid)
No
It clearly said recoiling nucleus.

if its recoiling it mustve already emitted the alpha
2. (Original post by kingaaran)
What was the unit - I worked it out to be C^2 kg^(-2)?
Yeah i got that too
3. (Original post by Mattematics)
I put -5Q, for the first one, was there a positive version?

I also put -4 for the second one.
I put the +5Q because I thought potential was a scalar but I have no idea now
4. For anyone wondering how to do the question about rearranging to find Ealpha (sorry it's a mess)

E = KEnucleus + Ealpha

V = -mv/N --> V^2 = m^2 v^2 / N^2

v = -VN/m --> v^2 = V^2 N^2 / m^2

KEnucleus = 1/2 N V^2 = 1/2 N (m^2 v^2 / N^2) = 1/2 m^2 v^2 / N

Ealpha = 1/2 m v^2 --> v^2 = 2*Ealpha / mE = 1/2 m^2 v^2 / N + Ealpha

E = 1/2 m^2 (2*Ealpha / m) / N + Ealpha

E = m*Ealpha / N + Ealpha

E = Ealpha (m/N + 1)

Ealpha = E (1 / (m/N + 1))

Ealpha = (N / (m + N))*E

Also here's a poll http://www.thestudentroom.co.uk/show....php?t=4176490
5. (Original post by jjarra1997)
I'm confused 😭😩 what question require you to work out energy for the capacitors? Cause I literally don't remember working out energy at all :s
it was a MCQ where they gave us a capacitor which had a min and max value
6. (Original post by aelahi23)
pendulum
7. (Original post by TheLazyGuy1)
Yeah i got that too
I dunno what the actual answer was but I put A because there were only about 3 A's out of 25 otherwise
8. (Original post by duncant)
what was the question again? I said he would to times his value of g by 4 to get the correct answer, is this right?
I'm afraid it's the other way around. He would have had to divide his value for g by 4 to get the real value of g. In other words, his answer was 4 times bigger than the real value.
9. I put -3Q/4pier on one of the multiple choice ones.
10. (Original post by Maligaha)
It asked for the direction of the force on x which was indeed y to x
Yeah thats right
11. Such a nice paper I don't know how I made so many mistakes 😂😭

Pretty sure I did better in the multiple choice
12. (Original post by Questioner1234)
Thats what i put but like 5 people below this have said otherwise
Oops sorry I meant 2F since 2x-1 before and 4x1 after, I hope I ticked the right one!
13. For the limitation I put dampening due to air resistance? Also on the MC, for the pendulum which one would have the largest amplitude? Overall I found section B okay, but the MC tricky.
14. (Original post by particlestudent)
Ergh I done my graph like this, anyone else done it like this -_-
yes.. i got something like that but i didnt go all the way down to zero... i stopped just before zero.. we should get atleast a mark for the shape of curve
15. (Original post by Questioner1234)
I dunno what the actual answer was but I put A because there were only about 3 A's out of 25 otherwise
Yeah it was A
16. (Original post by Mango Milkshake)
1st one

area under graph
Oh right, thanks
17. does anyone remember all 25 questions (not just the letters)?
18. (Original post by jovdawesome)
it was a MCQ where they gave us a capacitor which had a min and max value
OMG thanks yeah i remember now! It was literally killing me that I couldn't remember, thought I skipped a Q Lool
19. (Original post by jovdawesome)
yes.. i got something like that but i didnt go all the way down to zero... i stopped just before zero.. we should get atleast a mark for the shape of curve
But eventually the gravitational field strength does become zero? It's a vector...
I don't know if I done the shape correct, I think it should have had a decreasing gradient rather than increasing
20. (Original post by ombtom)
For anyone wondering how to do the question about rearranging to find Ealpha (sorry it's a mess)

E = KEnucleus + Ealpha

V = -mv/N --> V^2 = m^2 v^2 / N^2

v = -VN/m --> v^2 = V^2 N^2 / m^2

KEnucleus = 1/2 N V^2 = 1/2 N (m^2 v^2 / N^2) = 1/2 m^2 v^2 / N

Ealpha = 1/2 m v^2 --> v^2 = 2*Ealpha / mE = 1/2 m^2 v^2 / N + Ealpha

E = 1/2 m^2 (2*Ealpha / m) / N + Ealpha

E = m*Ealpha / N + Ealpha

E = Ealpha (m/N + 1)

Ealpha = E (1 / (m/N + 1))

Ealpha = (N / (m + N))*E

Also here's a poll http://www.thestudentroom.co.uk/show....php?t=4176490
That question was a disgusting question

(Original post by Hattie28)
For the limitation I put dampening due to air resistance? Also on the MC, for the pendulum which one would have the largest amplitude? Overall I found section B okay, but the MC tricky.
I talked about angles under 10 degrees.

What was the answer to the worded question about momentum in a system?

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