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

1. (Original post by terminatorsb)
Only less 2 hours left for exam Guys!!!!Good Luck all the physics students on TSR
3hours for me What I've always wanted to know is how can they stop my imaginary friend who lives in a far away country and sits the paper 2hrs before me, ringing me up and telling me all on the paper?

2. (Original post by lilangel890)
3hours for me What I've always wanted to know is how can they stop my imaginary friend who lives in a far away country and sits the paper 2hrs before me, ringing me up and telling me all on the paper?

there's quite a few known posters in this thread who sit the paper outside UK.
3. I wish i had a friend who told me the whole paper too....bad luck!!!!
4. I don't want to make silly mistakes like I did for unit 4 !!!
5. true nor do i
also i found the june 2010 unit 4 hard
is tht the one u did??
6. (Original post by JayAyy)
I'll probs do what I do best: make up a random experiment and explain it well
Dunno if it will get me marks though
I often find that the experiments can be made just by reasoning and what apparatus to use.
When faced with a practical experiment question, think about these!

• What am I going to change and what am I going to measure?
• What apparatus will I use to take measurements?
• How am I going to change one of the variables and determine the other?
• How can I collect data?
• How can I use the data to demonstrate something?
• What precuation could I take in the experiment to ensure my results are reliable?

I hope we get an experiment question on SHM. Basically you could use a data logger connected to a motion sensor which lies below a spring mass oscillator. Just set up the motion sensor so that the computer records [distance from sensor] against [time] and you can also use a similar technique to work out the acceleration. Then you can use known values of acceleration (a) and displacement (x) to plot a graph of a against x. It should be a straight line passing through the origin with a negative gradient. The gradient will have a value of -w² so that a = -w²x (so motion is SHM).
7. Hmm hope we don't need to know off by heart how to convert Astronomical Units and Parsecs to meters and that they'd just tell us what it is on the paper. Cause I haven't bothered trying to remember.
8. oh gawd im bricking it

on a side note, how would you answer the question:
What is the critical density

And goodluck guys
9. I wish I'd be able to do the paper already! I want to get on with my holiday!

(Original post by dana.h)
guys someone explain me the example in astrophysics on page 188 the centauri
Basically, they give you the value of the angle of earth-star-earth, you have to first divide by 2 so it's earth-star-sun and then convert this into degrees (1/3600), now you can just sub it into:
d = r/tanx
where r is the distance from the earth to the sun. -_- and not the radius.
10. (Original post by Uberuvy)
oh gawd im bricking it

on a side note, how would you answer the question:
What is the critical density

And goodluck guys
Critical density is the density at which the universe will have a very boring end the gravitational pull of the universe is equal to the density, therefore, the universe will not expand or contract anymore.

Or something like that.

(Original post by Sasukekun)
Hmm hope we don't need to know off by heart how to convert Astronomical Units and Parsecs to meters and that they'd just tell us what it is on the paper. Cause I haven't bothered trying to remember.
I hate that part of this unit with a passion. Why oh why can we not have one stupid universal unit?

Good luck everyone!
11. (Original post by unamed)

I hate that part of this unit with a passion. Why oh why can we not have one stupid universal unit?

Good luck everyone!
Lol I'm too scared to actually learn it, I feel that if I remember how to convert them I'll forget something else very important about Physics.
12. (Original post by Sasukekun)
Lol I'm too scared to actually learn it, I feel that if I remember how to convert them I'll forget something else very important about Physics.
Fair enough, you can do it the long way, work it out using the parallax formula. [parsec]
and an AMU is simply Earth->Sun

Oh, that reminds me, do they give us the distance from the Earth-> Sun?
or do we have to remember it?

Also, I'm only now doing the sample. If anyone can please quickly explain"

Astronomers discovered the planet by observing the “Doppler Wobble” effect. As the planet orbits the star, light from the star undergoes a Doppler shift in its frequency.
Explain why this method is likely to only detect very large planets.

Because of the presence of the planet, the star HD70642 does not remain at rest. Instead, the planet and star both orbit around their common centre of mass.
Explain why the orbiting speed of the star is very small in comparison to the speed of the planet.

The MCQ with rocket speed against time of universe or words to this effect.

Hope I know enough for a nice solid B and A overall ! WOOOOO!
14. Do we seriously need to know how to convert between parsecs/AU etc?
15. (Original post by Sasukekun)
Hmm hope we don't need to know off by heart how to convert Astronomical Units and Parsecs to meters and that they'd just tell us what it is on the paper. Cause I haven't bothered trying to remember.
Tell us.
16. I think the only distance conversion we need to know is 1lightyear to m. Possible what is one parsec (1/3600degrees)
17. (Original post by Doughboy)

none do. It's just that the Hubble constant is changeable due to gravity (think about it, the stronger the force of the gravity, the lower the recessional velocity). And also, we know that if the density of the universe is greater than the critical density, making the gravitational forces stronger, the universe will implode. < as the recessional velocities will be lower. Hence, Hubble can be linked to gravity and density. {I hope that made sense}

Also, I'm only now doing the sample. If anyone can please quickly explain"

Astronomers discovered the planet by observing the “Doppler Wobble” effect. As the planet orbits the star, light from the star undergoes a Doppler shift in its frequency.
Explain why this method is likely to only detect very large planets.

Because of the presence of the planet, the star HD70642 does not remain at rest. Instead, the planet and star both orbit around their common centre of mass.
Explain why the orbiting speed of the star is very small in comparison to the speed of the planet.

because the planet will move further, it's orbit's greater. Star is heavier, it won't be able to move as fast/much.

The MCQ with rocket speed against time of universe or words to this effect.
that's some sort of mistake. It's just supposed to be the speed vs time. the universe thing seems to be a part of another [non existent] question.

Hope I know enough for a nice solid B and A overall ! WOOOOO!
You'll do fine.
18. (Original post by Doughboy)

Also, I'm only now doing the sample. If anyone can please quickly explain"

Astronomers discovered the planet by observing the “Doppler Wobble” effect. As the planet orbits the star, light from the star undergoes a Doppler shift in its frequency.
Explain why this method is likely to only detect very large planets.

Because of the presence of the planet, the star HD70642 does not remain at rest. Instead, the planet and star both orbit around their common centre of mass.
Explain why the orbiting speed of the star is very small in comparison to the speed of the planet.

The MCQ with rocket speed against time of universe or words to this effect.

Hope I know enough for a nice solid B and A overall ! WOOOOO!

ok
its P(density row)=3H^2/8piG

19. (Original post by samydude)
ok
its P(density row)=3H^2/8piG

thankfully, we don't need to know that.
20. (Original post by unamed)
thankfully, we don't need to know that.
Thats what you THINK !

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