A2 Physics Unit 4 and 5 Revision Thread

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okay, so let's get talking about unit 5 :P I know nothing absolutely nothing right now, so I need to start revising pretty hard

what optional module are you guys doing?

Reply 141

LadySmythe

Please be vigilant - if you see any Unit 4 discussion please report it. I don't really want the thread closed until midnight due to a few silly people spoiling it for everyone else (this applies to edexcel discussion only)

Reply 142

Rosie2039

Help with this question please. :smile:

An ideal gas is heated from 300K to 600K. By what factor does the average speed of its molecules change?

Reply 143

Vampire-Love4ever

Original post by Rosie2039

Help with this question please. :smile:

An ideal gas is heated from 300K to 600K. By what factor does the average speed of its molecules change?

Use:

1/2*m*v^2 = 3/2 KT

Increasing T by a 2 increases v by a factor of 'square root (2)'

Then v increases by 1.4ms^-1.

I got it now only. :p:

Reply 144

Rosie2039

Can anyone explain the mechanism of nuclear fusion and the need for high denisties of matter and high temperature to bring it about and maintain it?

Reply 145

HollyJayne

Original post by paul10

Are you able to sit unit 5 in january or does aqa only set unit 5 for the summer???

If your with Edexcel then i think you can :smile:

Reply 146

HollyJayne

Original post by Rosie2039

Can anyone explain the mechanism of nuclear fusion and the need for high denisties of matter and high temperature to bring it about and maintain it?

Fusion - in stars its usually 2 hydrogen nuclei into helium :smile:

[im sure you know that]

- high densities are needed to increase the collision rate
- high temperature needed to "excite" the molecules more - making them gain kietic energy and again increasing collision rate

both of these need to be maintained otherwise the balance in radiation pressure and gravitational force would not remain - causing the whole red giant/supergiant, white dwarf, supernova, neutron star/back hole sequance would occur :smile:

hope its not to late! :biggrin:

Reply 147

Rosie2039

Original post by HollyJayne

Fusion - in stars its usually 2 hydrogen nuclei into helium :smile:

hope its not to late! :biggrin:

Thanks a lot :smile:

Reply 148

soutioirsim

Original post by Rosie2039

Thanks a lot :smile:

Just to add in as well, you need to mention that the two nuclei have positive charges so they repel each other, that's why you need the high energy :smile:

Reply 149

Rosie2039

Original post by soutioirsim

Just to add in as well, you need to mention that the two nuclei have positive charges so they repel each other, that's why you need the high energy :smile:

howz prep? ready for tomorrow? :tongue:

Reply 150

soutioirsim

Original post by Rosie2039

howz prep? ready for tomorrow? :tongue:

It's getting there, I know the topics quite well, I just hate the big wordy questions on stuff that you have to "apply your knowledge". That normally completely random :p:

What about you?

Reply 151

Rosie2039

Original post by soutioirsim

It's getting there, I know the topics quite well, I just hate the big wordy questions on stuff that you have to "apply your knowledge". That normally completely random :p: