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# 2016 | OCR A2 Advancing Physics B | G494 &amp; G495 | 20th &amp; 28th June watch

1. (Original post by notrodash)
So the answer was line A? Because in that case I got it right without even reading the question properly… Just now I realised that I wasn't even looking at the numbers, hopefully I don't do that in the G495 exam
Yes I am pretty sure A was correct.
2. (Original post by terpanter)
Im so sorry, can anyone please tell me what are earlier questions for bolzman/helium about? Im scared i miss a page
Can't remember it in full but one part of the question was something like "explain how helium particles at the same altitude can have a range of energies", and you had to talk about the usual collisions with air molecules (and other helium particles) transfer momentum and energy, and how successive collisions can cause an atom's energy to significantly exceed or fall below the average KT.

I believe the last bit, just after, was "a student claims helium particles will leave the atmosphere. Using the Boltzmann factor (it gave it to you), discuss this shizzle", and then you have to discuss that shizzle.

The very first question was a gravitational potential energy question, so you took the value calculated in (i) and used it as your epsilon (curly E in e^-(E/kT)). I ended up with something to the power of negative 47, and concluded that the probability of a particle leaving the atmosphere is very low but will happen due to the large number of particles and rate of collision, or something like that.

It spanned a full two pages so I'd be surprised if you did miss it mate. You're probably just omitting it from memory. You might have just missed the mention of helium and applied it to "a particle", which would probably only lose you the odd mark here and there.
3. this is what i remember getting

1a. Nkg^-1
b. Ns and Kgms^-1

2. i said C but looking back im not sure

3a. 0.5
b. 8

4. showing pv/t is constant at around 1.94, 1.87, 1.93

5.

6. draw cos(x) graph for accel and -cos(x) for displacment

7. red shift shows galaxies have a recessional velocities and are moving away so everything was at the same point at the begining of the universe.

8. speed is 1.8x10^8
b. gamma factor as 1.25
c. half life at rest 4ns

9. half life not constant so not exponentially decaying. show values

equate f=mv^2/r and f=gmm/r^2
mass as 1.83x10^27
sketch of rough velocity of moon follows a rough cos graph starting at A with max velocity

boltzmazman factor questions: probability of a particle having extra energy due to randoms collision with other particles changing energy, velocity and direction.

12a. force on outside due to change of momentum. less particles in tube so less change of momentum so less force so overall force in a upwards direction holding the plate in place.
b. pressure =17kPa
(maybe 100-17)

13a. 0.18 J
b. velocity of bullet 171ms
c. ke not copnserved speed at begining of movement was 2.12ms^-1
d. reason ke isnt conserved because its a elastic collision. energy is lost when bullet is embedded in blu tack. also energy loss due to heat of impact
4. (Original post by Busted838)
this is what i remember getting

1a. Nkg^-1
b. Ns and Kgms^-1

2. i said C but looking back im not sure

3a. 0.5
b. 8

4. showing pv/t is constant at around 1.94, 1.87, 1.93

5.

6. draw cos(x) graph for accel and -cos(x) for displacment

7. red shift shows galaxies have a recessional velocities and are moving away so everything was at the same point at the begining of the universe.

8. speed is 1.8x10^8
b. gamma factor as 1.25
c. half life at rest 4ns

9. half life not constant so not exponentially decaying. show values

equate f=mv^2/r and f=gmm/r^2
mass as 1.83x10^27
sketch of rough velocity of moon follows a rough cos graph starting at A with max velocity

boltzmazman factor questions: probability of a particle having extra energy due to randoms collision with other particles changing energy, velocity and direction.

12a. force on outside due to change of momentum. less particles in tube so less change of momentum so less force so overall force in a upwards direction holding the plate in place.
b. pressure =17kPa
(maybe 100-17)

13a. 0.18 J
b. velocity of bullet 171ms
c. ke not copnserved speed at begining of movement was 2.12ms^-1
d. reason ke isnt conserved because its a elastic collision. energy is lost when bullet is embedded in blu tack. also energy loss due to heat of impact
i got this except A for 2
5. (Original post by Busted838)
this is what i remember getting

12
b. pressure =17kPa
(maybe 100-17)
I am fairly certain it was 100-17= 83 kPa as the question said that the pressure was roughly 20 kPa less than normal.
6. (Original post by NamelessPersona)
I am fairly certain it was 100-17= 83 kPa as the question said that the pressure was roughly 20 kPa less than normal.
i read that in the question but was unsure to take it away or not. i just ended going with my worked answer. either way its only a mark!
7. You had to work out the half life at rest?
8. (Original post by kennz)
You had to work out the half life at rest?
Yeah you did; I made the same mistake
9. (Original post by kennz)
You had to work out the half life at rest?
Ye. It gave you the half-life at speed (call it t), accounting for relativity, and in the previous part you'd worked out the gamma factor, γ (if I remember correctly).

Then I believe you had to apply t = t0 x γ to find the half-life at rest, wherein t0 is said half-life at rest. t0 = t / γ is what I ended up using.

It was a 2-3 marker, so not the end of the world.
10. (Original post by WhiteBison)
Ye. It gave you the half-life at speed (call it t), accounting for relativity, and in the previous part you'd worked out the gamma factor, γ (if I remember correctly).

Then I believe you had to apply t = t0 x γ to find the half-life at rest, wherein t0 is said half-life at rest. t0 = t / γ is what I ended up using.

It was a 2-3 marker, so not the end of the world.
ah ok it was 3 marks then as I added up the total marks, Im such an idiot
11. (Original post by Busted838)
i read that in the question but was unsure to take it away or not. i just ended going with my worked answer. either way its only a mark!
12. (Original post by kennz)
ah ok it was 3 marks then as I added up the total marks, Im such an idiot
It happens to us all mate.
13. You know if it's an easier paper when there's no "Hitler reacts" video hahaha

Man I hope I got most of the ones I answered right. I asked the invigilators if I could maybe take the exam later due to the extreme head pain, but no such luck. A literal shrug of the shoulders was my help.
14. (Original post by Busted838)
this is what i remember getting

1a. Nkg^-1
b. Ns and Kgms^-1

2. i said C but looking back im not sure

3a. 0.5
b. 8

4. showing pv/t is constant at around 1.94, 1.87, 1.93

5.

6. draw cos(x) graph for accel and -cos(x) for displacment

7. red shift shows galaxies have a recessional velocities and are moving away so everything was at the same point at the begining of the universe.

8. speed is 1.8x10^8
b. gamma factor as 1.25
c. half life at rest 4ns

9. half life not constant so not exponentially decaying. show values

equate f=mv^2/r and f=gmm/r^2
mass as 1.83x10^27
sketch of rough velocity of moon follows a rough cos graph starting at A with max velocity

boltzmazman factor questions: probability of a particle having extra energy due to randoms collision with other particles changing energy, velocity and direction.

12a. force on outside due to change of momentum. less particles in tube so less change of momentum so less force so overall force in a upwards direction holding the plate in place.
b. pressure =17kPa
(maybe 100-17)

13a. 0.18 J
b. velocity of bullet 171ms
c. ke not copnserved speed at begining of movement was 2.12ms^-1
d. reason ke isnt conserved because its a elastic collision. energy is lost when bullet is embedded in blu tack. also energy loss due to heat of impact
For question 9 I showed that dI/dt was not proportional to I (I think it was I, or whatever it was) - do you think that would still get the mark?
15. (Original post by ThatPerson2)
For question 9 I showed that dI/dt was not proportional to I (I think it was I, or whatever it was) - do you think that would still get the mark?
That seems reasonable - I believe it would. Kind of a pain on your part though!
16. (Original post by WhiteBison)
That seems reasonable - I believe it would. Kind of a pain on your part though!
Thanks. It was mainly because I looked at the question and it was about capacitor discharge so I assumed they would want the 37% instead, and the second 37% section was below the bottom of the graph, and I didn't think of doing it with half lives! Ah well.
17. Would you get any marks for on 9 for showing adjacent values of charge at equal time intervals are roughly similar??
18. Easy paper all in all, section A was a bit more involved than usual but the orbits, Boltzmann and momentum questions were easy/standard.
19. I'm so annoyed with myself, for the bullet question I had 170m/s as the speed. I then did the next bit about energies but didn't get the numbers to make sense so went back to the bullet one. I thought for some reason I'd worked it out wrong, so changed it all, so now my answers wrong.... so that's no marls for the bullet speed or the energy question after it.

My chances of an A are dropping
20. Boundary predictions? A* around 50 ish maybe idk

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