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

Is there any sort of unofficial mark scheme for PHYA1? The PHYA4 was really well put together considering we were all students lol

Reply 2261

Haza100

1

So I just stumbled upon this in a revision guide, is this 100% the way you would ascertain the energy released in a reaction given the graph of binding energy per nucleon?

E.g. instead of doing (BEPN of Helium-4) - (BEPN of He-3 + BEPN of He-2), you take the average between He-3 and He-2 to find the 'average increase', then multiply by the number of nucleons?

Reply 2262

betbi3etwerrd

2

Original post by Haza100

So I just stumbled upon this in a revision guide, is this 100% the way you would ascertain the energy released in a reaction given the graph of binding energy per nucleon?

E.g. instead of doing (BEPN of Helium-4) - (BEPN of He-3 + BEPN of He-2), you take the average between He-3 and He-2 to find the 'average increase', then multiply by the number of nucleons?

This is very approximate result

Reply 2263

_Caz_

10

What is the definition of parallax? I've seen a few of them around and I want to make sure I have the right wording because you know how picky they can be with their definitions

Reply 2264

Absent Agent

21

Original post by Jimmy20002012

Anyone?

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Try this, and let me know if you get the correct ratio
ImageUploadedByStudent Room1434562395.955636.jpg

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Reply 2265

davidharris96

1

I feel like not having been able to revise Astro since before my first exam has affected me, less confident now than I was two weeks ago! Bricking it for this exam,
Anyone else feel the same?
All the numbers like masses of stars in main sequence etc have gone from my head

Reply 2266

CD223

OP

10

Original post by _Caz_

What is the definition of parallax? I've seen a few of them around and I want to make sure I have the right wording because you know how picky they can be with their definitions

Parallax itself is the shift in the apparent position of an object depending on the relative position between the object and observer.

In terms of observing stars, it is used for estimating distances to nearby stars as the nearby stars shift in position relative to a backdrop of more distant stars.

The angular shift in the line of sight from Earth to the object of interest over 6 months is halved to get the parallax angle, which is used to find the distance to the object.

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Reply 2267

thedontom

1

Lamb is the constant of proportionality and the fraction of ..... I forgot the rest :/

Reply 2268

_Caz_

10

Original post by CD223

Parallax itself is the shift in the apparent position of an object depending on the relative position between the object and observer.

In terms of observing stars, it is used for estimating distances to nearby stars as the nearby stars shift in position relative to a backdrop of more distant stars.

The angular shift in the line of sight from Earth to the object of interest over 6 months is halved to get the parallax angle, which is used to find the distance to the object.

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Ah okay - thank you! :smile:

Reply 2269

AaronA330

1

Original post by SuperMushroom

Can anyone explain question 2 a ii

I dont get how you can answer it knowing only 1 piece of information?

http://filestore.aqa.org.uk/subjects/AQA-PHYA51-QP-JUN14.PDF

Use the equation N=No e^-yt

Change it for what you've got, 0.375N=Ne^-yt

Divide both sides by N to get 0.375=e^-yt

Use your log laws to get t on its own as you worked y out in the previous question.

Reply 2270

_Caz_

10

Original post by thedontom

Lamb is the constant of proportionality and the fraction of ..... I forgot the rest :/

is this the decay constant, lambda, you're talking about?

if so, you can say the decay constant is the probability that nucleus will decay in a given unit time. :smile:

Reply 2271

SuperMushroom

9

Original post by AaronA330

Use the equation N=No e^-yt

Change it for what you've got, 0.375N=Ne^-yt

Divide both sides by N to get 0.375=e^-yt

Use your log laws to get t on its own as you worked y out in the previous question.

Thanks i have got it now :biggrin:

Reply 2272

SuperMushroom

9

For Astrophysics tomorrow i think the 6 marker will be on the life cycle of a star and what happens 2 stars of different solar masses

Reply 2273

thedontom

1

Original post by _Caz_

is this the decay constant, lambda, you're talking about?

if so, you can say the decay constant is the probability that nucleus will decay in a given unit time. :smile:

Lambda* xD Thank you! :smile:

Reply 2274

CD223

OP

10

What will the six marker be on?

VOTE HERE:
http://www.poll-maker.com/poll340727x7b2b4474-13

Good luck tomorrow guys!

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Reply 2275

AR_95

21

Just a note

Ionisation Chambers, and Radiation monitoring could also come up tomorrow

Reply 2276

Absent Agent

21

Original post by Jimmy20002012

Can anyone help me on second part of this question doing turning points don't seem to know how to do it?

ImageUploadedByStudent Room1434559496.197379.jpg

ImageUploadedByStudent Room1434559496.197379.jpg

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Sorry, i derived the equation incorrectly, my mind is shut down
ImageUploadedByStudent Room1434563035.568777.jpg

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Reply 2277

SuperMushroom

9

Original post by CD223

What will the six marker be on?

VOTE HERE:
http://www.poll-maker.com/poll340727x7b2b4474-13

Good luck tomorrow guys!

Posted from TSR Mobile

Can you add my option i suggested? about the life cycle of a star and what happens at different solar masses, i personally think its a great 6 marker and could
certainly come up

Reply 2278

jackcros

When talking about discharge tubes, during the discovery of electrons, some revision notes say they are produced through thermionic emission from the cathode, but others say the electrons come from the low pressure gas in the tubes being ionised due to the high potential difference, releasing electrons in the process.

Which is correct and in which context are they needed?

Reply 2279

Sbarron

3

What's diminished please?

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

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