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# Official OCR A2 G484 June 2016 [Module 1] [90UMS] watch

1. (Original post by speed1✈️✈️)
Plant? , do you mean planet

I got something in the order of 10^33, I used Kepler's 3rd law and radius R2 and time period given in question, converted into seconds.
God I hope we're both right on this one :O
2. (Original post by Kevinwong)
And mass of the plant was?
something BIG

I got 1.0...x10^33 I can't remember the decimals
3. (Original post by Danny.L)
God I hope we're both right on this one :O
SAME, just gota pray that TeacherCol agrees

Shame we might have to wait till tomorrow though, I would have forgotten my answers
4. (Original post by speed1✈️✈️)
Plant? , do you mean planet

I got something in the order of 10^33, I used Kepler's 3rd law and radius R2 and time period given in question, converted into seconds.
Did the second part of the question say the period of S1 was 3 days? I used Keplar's law with R1 and T1 to get M1 and then used the ratio to get M2 but I think I may have made a mistake . Would I still get 1/2 marks?
5. (Original post by Pyslocke)
Did the second part of the question say the period of S1 was 3 days? I used Keplar's law with R1 and T1 to get M1 and then used the ratio to get M2 but I think I may have made a mistake . Would I still get 1/2 marks?
3 days????? How???? I never saw that. I am pretty damn certain it was 4 days. I don't know if you would to be honest
6. (Original post by saal180898)
something BIG

I got 1.0...x10^33 I can't remember the decimals
Yep it was you're right

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7. (Original post by speed1✈️✈️)
3 days????? How???? I never saw that. I am pretty damn certain it was 4 days. I don't know if you would to be honest
It was 4 days

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8. (Original post by Pyslocke)
Did the second part of the question say the period of S1 was 3 days? I used Keplar's law with R1 and T1 to get M1 and then used the ratio to get M2 but I think I may have made a mistake . Would I still get 1/2 marks?
Well, they told you the period was equal for both of them, 4 days.
I've no idea if that is right.
I just used keplers third law with T^2 = (4Pi^2 * R2^3)/(G*M2)
That got me 1.73*10^33.
Was it out of 2 or 3?
9. (Original post by speed1✈️✈️)
3 days????? How???? I never saw that. I am pretty damn certain it was 4 days. I don't know if you would to be honest
Oh wait my mistake. It was 4 day
10. (Original post by Danny.L)
Well, they told you the period was equal for both of them, 4 days.
I've no idea if that is right.
I just used keplers third law with T^2 = (4Pi^2 * R2^3)/(G*M2)
That got me 1.73*10^33.
Was it out of 2 or 3?
It was worth 3 marks
11. (Original post by Danny.L)
Well, they told you the period was equal for both of them, 4 days.
I've no idea if that is right.
I just used keplers third law with T^2 = (4Pi^2 * R2^3)/(G*M2)
That got me 1.73*10^33.
Was it out of 2 or 3?
I forgot they had the same period >.<. I think I got 10^31. But how come I don't get the same answer?
12. (Original post by Pyslocke)
I forgot they had the same period >.<. I think I got 10^31. But how come I don't get the same answer?
The question clearly stated both stars had the same period
13. (Original post by Pyslocke)
I forgot they were the same period >.<. I think I got 10^31. But how come I don't get the same answer?
Yeah a couple people in my class got that too. I've done it like 10 times and I consistently get 10^33, perhaps you mis-entered something on your calculator?
14. (Original post by LibertyMan)
What were your values for S2 people??? I NEED TO KNOW FUSUFBAKFJKDNDKIDJFJ
I think it was 1.74x10^33
15. Workings to get the mass of S2 for those wondering.
Attached Images

16. (Original post by Danny.L)
c?
because when you use kepler's third law the mass you calculated is the capital M not small m. in this case that will be mass c, the centre of rotation.
17. If I got 7.2x10^12 and 2.4x10^12, do i lose one or two marks? Please answer :9
That means nothing to me do you mean I'll lose M1 and A1 (2 marks) or get M1 and A1 (lose 1 mark)? Have to admit it makes me chuckle, can't wait to see the Hitler video!
i think both
19. (Original post by speed1✈️✈️)
Really doesn't deserve one to be honest, wasn't as bad as people saying! There have been MUCH worser exams set by OCR - (cough cough G481 June 2015). This years OCR papers seem to be half descent!
imo this is worse than g481 june 2015
20. (Original post by saal180898)
? I thought it said the the distance between the two stars (R1 + R2) = 4.8x10^12
I am 100% sure that this person Is correct. I read it very carefully. You were supposed to get that equation shown above and that raito, what was it 3R1=R2 or something, then solve simultaneously. it came out with R1=1.2x10^12 and R2=3.6x10^12.

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