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# A2 Physics Unit 5 ~ 18th June 2012

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1. Re: A2 Physics Unit 5 ~ 18th June 2012
(Original post by Parthenon93)
The parallax angle to Barnard's star is 0.545''. How far away is the star in metres?

I get 5.68 x 10^16m, but the answer given is 1.14 x 10^17m.

may be the answer given is wrong...i dont know...
i mean this is how it should be done,...right???

parallex angle = 0.545

1" = 1/3600
0.545" = x
x = 1.51x10^-4

d=r/tan(theta)
d= (1.5x10^-4) / tan(1.51x10^-4)
d= 5.69x10^16 m

please someone correct me if I'm wrong....
2. Re: A2 Physics Unit 5 ~ 18th June 2012
(Original post by King_Arthur)
if only i can get hold of these notes ...
http://www.educationusingpowerpoint...._Collapse.html
arrghhh! have to pay???? i don't have a credit card
3. Re: A2 Physics Unit 5 ~ 18th June 2012
(Original post by Parthenon93)
The parallax angle to Barnard's star is 0.545''. How far away is the star in metres?

I get 5.68 x 10^16m, but the answer given is 1.14 x 10^17m.

you have divide the angle by 2 u haven't done that

workings

d=(1.5/10^11)/tan(.545/(2*3600))
= 1.4*10^17

do u want further explanation ??????????????????????
4. Re: A2 Physics Unit 5 ~ 18th June 2012
(Original post by cisne)
may be the answer given is wrong...i dont know...
i mean this is how it should be done,...right???

parallex angle = 0.545

1" = 1/3600
0.545" = x
x = 1.51x10^-4

d=r/tan(theta)
d= (1.5x10^-4) / tan(1.51x10^-4)
d= 5.69x10^16 m

please someone correct me if I'm wrong....

ur wrong i have posted the correct workings
5. Re: A2 Physics Unit 5 ~ 18th June 2012
(Original post by King_Arthur)
ur wrong i have posted the correct workings
thanks...my teacher marked it as a right answer
6. Re: A2 Physics Unit 5 ~ 18th June 2012
(Original post by cisne)
thanks...my teacher marked it as a right answer
small correction
but weather to divide the angle depends in what angle they have given i assumed that the angle given was double the parralex angle as measure in a gap of 6 months just to clarify was this a past paper question so i can confirm my assumption
7. Re: A2 Physics Unit 5 ~ 18th June 2012
(Original post by King_Arthur)
small correction
but weather to divide the angle depends in what angle they have given i assumed that the angle given was double the parralex angle as measure in a gap of 6 months just to clarify was this a past paper question so i can confirm my assumption
It is the Miles Hudson book page 191.

I'll copy the exact question:

The parallax angle to Barnard's star is 0.545". How far away is Barnard's star in a. metres b. light years c. parsecs d. astronomical unit

It did not mention "after 6month period". How do we know when to divide and when not to divide?
8. Re: A2 Physics Unit 5 ~ 18th June 2012
(Original post by iesians)
why is iron the end product of all fusion and fission reactions ..?!
Maybe someone's already answered this but it's the most stable nucleus with the highest binding energy per nucleon.

EDIT: It also has the lowest possible energy state.
Last edited by TheGrinningSkull; 15-06-2012 at 18:41.
9. Re: A2 Physics Unit 5 ~ 18th June 2012
(Original post by TheGrinningSkull)
Maybe someone's already answered this but it's the most stable nucleus with the least binding energy per nucleon.
Shouldn't it be the highest binding energy per nucleon, therefore most stable?
10. Re: A2 Physics Unit 5 ~ 18th June 2012
(Original post by Parthenon93)
It is the Miles Hudson book page 191.

I'll copy the exact question:

The parallax angle to Barnard's star is 0.545". How far away is Barnard's star in a. metres b. light years c. parsecs d. astronomical unit

It did not mention "after 6month period". How do we know when to divide and when not to divide?

no in this case ur workings seems correct who told u it's wrong
11. Re: A2 Physics Unit 5 ~ 18th June 2012
(Original post by Parthenon93)
It is the Miles Hudson book page 191.

I'll copy the exact question:

The parallax angle to Barnard's star is 0.545". How far away is Barnard's star in a. metres b. light years c. parsecs d. astronomical unit

It did not mention "after 6month period". How do we know when to divide and when not to divide?
good question....i'll get mad before 22nd june if things are going same like this
Last edited by cisne; 15-06-2012 at 18:24.
12. Re: A2 Physics Unit 5 ~ 18th June 2012
Can anybody do a quick differenence between brightness, luminosity, intensity and radiation flux for me?

This is what I am on ...

Brightness = Radiation flux and is how much of the emitted energy we (at a certain distance away) from the black body.

Luminosity = Power and is the rate at which energy is emitted from the surface of the black body.

I don't know where to put intensity in all this.
Last edited by Parthenon93; 15-06-2012 at 18:28.
13. Re: A2 Physics Unit 5 ~ 18th June 2012
Power per unit area is intensity

luminosity total power emitted
14. Re: A2 Physics Unit 5 ~ 18th June 2012
(Original post by King_Arthur)
Power per unit area is intensity

luminosity total power emitted
So brightness/radiation flux is the intensity?
15. Re: A2 Physics Unit 5 ~ 18th June 2012
(Original post by King_Arthur)
Power per unit area is intensity

luminosity total power emitted
Could you please convert 1.4 x 10^17m to light years and parsecs for me? I think I am getting the wrong answers.
16. Re: A2 Physics Unit 5 ~ 18th June 2012
(Original post by Parthenon93)
Shouldn't it be the highest binding energy per nucleon, therefore most stable?
You're right, I got confused there, thanks for the correction.

Why is it sometimes you get the same graph inverted? It's really confusing when they invert it and you see the same y-axis label.

Maybe it was the one-off graph I seem to have seen or a bad label.
Last edited by TheGrinningSkull; 15-06-2012 at 18:44.
17. Re: A2 Physics Unit 5 ~ 18th June 2012
(Original post by Parthenon93)
Could you please convert 1.4 x 10^17m to light years and parsecs for me? I think I am getting the wrong answers.
is this correct??

1 LY = 9.46x1015m
d=1.4x1017/ 9.46x1015
d=14.8 LY

1pc = 3.26 LY
x pc= 14.8 LY
x= 4.53 pc

1AU = 1.5x1011m
x AU= 1.4x1017
x = 9.33x105 AU
???????????????????????????????? ???????
18. Re: A2 Physics Unit 5 ~ 18th June 2012
(Original post by Parthenon93)
Shouldn't it be the highest binding energy per nucleon, therefore most stable?
You are correct there.
19. Re: A2 Physics Unit 5 ~ 18th June 2012
(Original post by cisne)
is this correct??

1 LY = 9.46x1015m
d=1.4x1017/ 9.46x1015
d=14.8 LY

1pc = 3.26 LY
x pc= 14.8 LY
x= 4.53 pc

1AU = 1.5x1011m
x AU= 1.4x1017
x = 9.33x105 AU
???????????????????????????????? ???????
Those are the exact answers I get The answer scheme says otherwise ... 12ly and 3.68pc ... I am beginning to think the answers are effed for this question.

I had this other question, where they said billion but considered million.
Last edited by Parthenon93; 15-06-2012 at 18:54.
20. Re: A2 Physics Unit 5 ~ 18th June 2012
(Original post by Parthenon93)
Those are the exact answers I get The answer scheme says otherwise ... 12ly and 3.68pc ... I am beginning to think the answers are effed for this question.

I had this other question, where they said billion but considered million.
owh.....is there anybody else who'd like to try this,...please???

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