Edexcel A2 Physics Unit 5 'Physics from Creation to Collapse'

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Reply 520

yadas

lefneosan

thanks for that. What do you mean by dice?

Check here. :wink:

Reply 521

yadas

OL1V3R

Can someone explain to me what a supernova is and how they are formed?

Also, I don't understand how the properties of a Cepheid variable relate to its Intensity/Time graph. Why will a more luminous Cepheid variable have a greater period of pulsation?

A supernova is a stellar explosion that is more energetic than a nova.
After the core of an aging massive star ceases generating energy from nuclear fusion, it may undergo sudden gravitational collapse into a neutron star or black hole, releasing gravitational potential energy that heats and expels the star's outer layers.
Supernovae are extremely luminous and cause a burst of radiation that often briefly outshines an entire galaxy, before fading from view over several weeks or months.

You can read further here. :smile:

Thought we might not be required to know that.
For Cepheids check wiki (one more) too.. :K:

A Cepheid is a member of a class of pulsating variable stars.
The relationship between a Cepheid variable's luminosity and pulsation period is quite precise, securing Cepheids as viable standard candles.
Their luminosity is directly related to their period of variation, the longer the pulsation period, the more luminous the star.

I think we dont really need that information, but if you are interested. :smile:

But we do need to know that we can use them as standard candles and their luminosity varies with time.

Reply 522

nnamdi

yadas

You can read further here. :smile:

Thought we might not be required to know that.
For Cepheids check wiki (one more) too.. :K:

I think we dont really need that information, but if you are interested. :smile:

But we do need to know that we can use them as standard candles and their luminosity varies with time.

yadas..isnt oliver havin those sessions again?

Reply 523

yadas

nnamdi

yadas..isnt oliver havin those sessions again?

You could ask him. :smile:

I dont think so. We have only 1 day left anyway.

Reply 524

Bronze92

lefneosan

thanks for that. What do you mean by dice?

how dice resemble the fact that nuclear decay is random, which means that it cannot be predicted which nucleus will decay next! And Spontaneous, unaffected by any external stimuli such as temperature.

Reply 525

kappleberry

yadas

From pV = NkT, V/T = Nk/p, where Nk/p is constant (N - number of molecues in the oven is constant, they dont open the oven and leave, p is at atmospheric pressure as they stated, k is constant on its own).
Hence V₁/T₁ = V₂/T₂. (1)
(Using 1 for 27°C and 2 for 227°C)
As density, ρ = m/V, V = m/ρ.
Substituting this into (1) gives:
m/ρ₁T₁ = m/ρ₂T₂
As mass is constant:
ρ₁T₁ = ρ₂T₂
We need the ratio of ρ₂/ρ₁ (at 227° to 27°C).
ρ₂/ρ₁ = T₁/T₂ = (272+27)/(273+227) = 300/500 = 0.6. :h:

I think the suggested experiments from the syllabus would be sufficient. :yes:

your method of explanation is amazingly thorough. THANK YOOU

Reply 526

Uberuvy

kappleberry

your method of explanation is amazingly thorough. THANK YOOU

I know, if he doesn't get an A then you know edexcel is playing with us :wink:

Reply 527

omegaSQU4RED

yadas

You could ask him. :smile:

I dont think so. We have only 1 day left anyway.

I'm not planning on having any more sessions, since we've gone through all the topics.

Although if anyone would like any more sessions, then let me know. :smile:

Reply 528

kappleberry

Uberuvy

I know, if he doesn't get an A then you know edexcel is playing with us :wink:

he sure as hell deserves it. Not just coz hes a genius, sharing what you know is hard for a lot of people.
Yadas, you're way cool :woo:

Reply 529

lefneosan

Bronze92

thanks! and also that yadas, top bloke.

Reply 530

kappleberry

unamed

I basically calculated the mass of air at 227 degrees (as you did in part (i)) and then the density using m/v of each.
Then you put the density at 227/27, which should give you around 0.6. :smile:

=] thnkyuss

Reply 531

kappleberry

Re the experiments. Does anyone know where I could get a quick link to jot down all the diagrams and basic points? Ive noted down some of them using the markscheme of papers, but I im in loss with diagrams.

Many many thankss

Reply 532

yadas

Oh, thanks guys.. :K:

kappleberry

I've heard practicalphysics.com was a good one, though I didnt get much into that myself.
If you have Hodder book I think it would be enough, there are quite nice and simple diagrams. :smile:

Miles Hudson's book also contains those.

Reply 533

samydude

kappleberry

Here you go : LINK

Reply 534

kappleberry

yadas

Oh, thanks guys.. :K:

I've heard practicalphysics.com was a good one, though I didnt get much into that myself.
If you have Hodder book I think it would be enough, there are good and simple diagrams. :smile:

We weren't given textbooks, never felt the need to use them, so didnt buy any either, Only use the cgp one. =/
Ill check the link thoo! thankss

Could you note down the isbn to that book please? Ill go get it tomorrow =]

Reply 535

kappleberry

samydude

Here you go : LINK

Thanks samy!

the files arent opening though...do I have to change the format or something?

Reply 536

yadas

kappleberry

Are you going to buy it for one day? :gasp:

9780340888070 - Tim Akrill
9781408206089 - Miles Hudson

The files there are Word, I think you know that. :smile:

What's the problem with them?

Reply 537

helooo19x

If something has a high binding energy per nucleon that another substance, is it more stable?

Reply 538

yadas

helooo19x

If something has a high binding energy per nucleon that another substance, is it more stable?

Check this link. (Not wiki. :biggrin:

)

In order to find a good indicator of stability of nuclides, we take a look at the average binding energy per nucleon, BE_ave.
This turns out to be a useful criterion for the stability of nuclides.