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OCR Physics A Cosmology
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Schmeevey
^^i got 3.65pc
yeah that was for d = 1/parallax but the question after, gave the absolute magnitude and the apparent was 0 and you needed to find distance, which i used that formula...
the hubble constant question was easier than i though it would be...
got the age of the universe to be 4 x 10^17s and thats right....i just said that, 1/Ho gave universe age and also critical density could be calculated from Ho...
they gave the absolute magnitude to be something like 0.58
The Apprentice
yeah that was for d = 1/parallax but the question after, gave the absolute magnitude and the apparent was 0 and you needed to find distance, which i used that formula...
Yeah so what did everyone get for the distance of Vega using the magnituide equation? I got 7.7 p.c
Charzhino
Yeah so what did everyone get for the distance of Vega using the magnituide equation? I got 7.7 p.c
yeah i got something like that...
Charzhino
Yeah so what did everyone get for the distance of Vega using the magnituide equation? I got 7.7 p.c
That's what I did...
apparent 0 absolute 0.58
M=m-5log(d/10)
0.58=0-5log(d/10)
0.58/-5=log(d/10)
0.77=d/10
d=7.7pc
ILoveComplexNumbers
That's what I did...
apparent 0 absolute 0.58
M=m-5log(d/10)
0.58=0-5log(d/10)
0.58/-5=log(d/10)
0.77=d/10
d=7.7pc
apparent 0 absolute 0.58
M=m-5log(d/10)
0.58=0-5log(d/10)
0.58/-5=log(d/10)
0.77=d/10
d=7.7pc
did you need to show all of that...because i just used the formula:
d = 10^((m-M+5)/5)
Charzhino
What did people get for velocity of earth. Around 1404 ms-1?
i got something like 200 and something ms-1...can't remember how i did it though...
Charzhino
What did people get for velocity of earth. Around 1404 ms-1?
Yep something like that. And regarding all the working I did, I dunno. Probably not.
Charzhino
Mean distance from earth to sun was 1101 x radius off earth.
2 pie r(m) / T(s)
2 pie r(m) / T(s)
stupid mistake...thats marks dropped there then...i will be happy if i get a c in this paper as i was dreading it due to a lack of revision....
For the question on critical density...because the critical density is used for the calculation. I thought if the new volume was greater therefore the critical density would decrease so the universe is more likely to be closed or flat.
As for the last synoptic question....if the radius increased by 2 surely the resistance would increase by 4 (R = pl/A) ?
As for the last synoptic question....if the radius increased by 2 surely the resistance would increase by 4 (R = pl/A) ?
ukebert
hmm, not bad altogether. I think some things went badly, some things went well. I wasn't sure of the whole atmosphere stuff, made it up, and I got 1.4ms^-1 for speed of Earth, which i think may be a little slow. The synoptic question was nice though.
Yea, I thought the atmosphere one was very odd indeed, can't see many doing well on it. I tried to recall what I knew from chemistry in it and made quite a bit up too.
timx
For the question on critical density...because the critical density is used for the calculation. I thought if the new volume was greater therefore the critical density would decrease so the universe is more likely to be closed or flat.
As for the last synoptic question....if the radius increased by 2 surely the resistance would increase by 4 (R = pl/A) ?
As for the last synoptic question....if the radius increased by 2 surely the resistance would increase by 4 (R = pl/A) ?
I also put that the universe would be closed/flat due to the critical density.
Yea I'm fairly sure I put that the resistance would increase fourfold too. Made a stupid mistake with the next one on the time taken because I managed to rearrange V=IR wrong lol.
Oh well, I only needed a U I think on that paper to get my uni offer, just depends whether I get an A or not now. Obviously depends how well the practical went though.
timx
For the question on critical density...because the critical density is used for the calculation. I thought if the new volume was greater therefore the critical density would decrease so the universe is more likely to be closed or flat.
if the volume was greater, the density is smaller, i.e. the density of the universe would be less than the critical density, so the universe continues to expand forever and ever and ever, approaching no limit.......therefore its open?
I thought that the universe is closed when density of universe is greater than the critical density, so would contract and end in the big crunch. is this right or have I got it muddled up?
hmm i think i screwed up the very last question. I also got that if the radius increases, the resistance decreases, time taken to heat decreases and i put frequence decreases because it gets stiffer, spring constant increases, but realised that it should increase. oh well. couldn't remember that the galaxy was elliptical, I put spherical
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