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# Official Thread For OCR Physics A G484 Jan 2011 Watch

1. thought it was an okay paper actually.

kilowatts is not in the specification though!?
why on earth did they put it in..
2. isn't the amplitube 5??

max displacement from mean position.

mean position is the when the sea is stable, at 13m, it moves up to 18, so making the amplitude 5...

saying the amplitude is 2.5 is implying the mean position of the wave somewhere in-between the the first half of the oscillation
3. (Original post by sc0307)
amplitude for the harbour question?

surely it was 18m cos that was the maximum depth?
Max depth was 18, min was 13, therefore it was oscillating between those two points.

We can say that exactly in between those two values is the equilibrium position.

Therefore, (18-13)/2 = 2.5

It sounds logical, not sure if it's right.
4. (Original post by FruitsPunchSamurai)
I got that as well, but when I was working out temperature in that question, I got a ridiculously large number. 1.5x10^26, I was thinking, "How is that even remotely possible?"

I got 2.5 for the amplitude question.

Yeh i did that, and got the exact same temp left it and went bk to it remembering KE is the same for both

i got 18 for the amplitude so stupid!! but thank god its 1 mark and error carried forward. that whole SHM question was really difficult especially the first parts :O
5. (Original post by CapsLocke)
really, I'm sure it's 5???
The top of the area of the container the tide filled was 18, and bottom was 13, so the max displacement EITHER SIDE of the equilibrium midpoint, was 2.5.
6. I got 2.5 for the amplitude but then did 18-2.5. WTF was i thinking!!!
7. (Original post by CapsLocke)
isn't the amplitube 5??

max displacement from mean position.

mean position is the when the sea is stable, at 13m, it moves up to 18, so making the amplitude 5...

saying the amplitude is 2.5 is implying the mean position of the wave somewhere in-between the the first half of the oscillation
no it was 2.5 as the graph would be cos to start at biggest posible negative and go up to maximum then back donw so mid point is 2.5 above 13
8. (Original post by CapsLocke)
isn't the amplitube 5??

max displacement from mean position.

mean position is the when the sea is stable, at 13m, it moves up to 18, so making the amplitude 5...

saying the amplitude is 2.5 is implying the mean position of the wave somewhere in-between the the first half of the oscillation
No, Low tide is 13m, High tide is 18m. The amplitude is distance from equilibrium = (18-13)/2 = 2.5.

I allmost didn't realise but got it in the end.
9. (Original post by sc0307)
amplitude for the harbour question?

surely it was 18m cos that was the maximum depth?
Its 2.5m, see the similar question in the SHM section of the book.

I got it wrong too, even after getting it wrong in the book
10. The question on calculating the momentum of the air was confusing. Did it want momentum for the whole 5 seconds of air? Or just for 1 second? I worked both out, but wrote the answer for 5.
11. If it's really 2.5 for amplitude. Then what the heck would it be if the tide raised even more in a different scenario?

You'd have to recalculate the entire tide. What the ****.

It's like saying the tides go down to 13 and up to 18. That's pretty bs. I thought tides go up and back down to initial which was 13.

They can't start at 15 and go down what the ****. Where would the rest of the compressed water go? I understand that the water can be LIFTED up to 18, but how can it start at 15 and go down to 13? So it should start at 13. And raise to 18.

@Above guy: I think they wanted 5, because the part 1 of that bit it said "the calculated mass" or something, which was 6000 which was for 5 seconds. So I used the 6000 throughout it. Physics papers are like so ****ing dumb, they're so ****. It's like a toned down version of M2 wtf and added some ****ty bits of Chemistry in.

More back on to my point about tides:

You have a tide like this

-------------------------, it can be RAISED by pulling the water up. But how the **** can you LOWER it less than 13, that's why minimum WAS 13 because its the lowest it can go?

What the **** SHM Up and down tides? They don't ****ing go up and down in 12.5 hours. I thought tides just swoosh up and go back down into its original position. Not up then down and further down (somehow compressing itself).
12. Kilowatt hour isn't even in our syllabus, and wasn't related to Newtonian world, why was it even there?
13. that paper was ridiculous. sooooo hard omg. did anyone find the radius of the satellites orbit easily? am i the only one who suffered?
14. (Original post by vxa1314)
If it's really 2.5 for amplitude. Then what the heck would it be if the tide raised even more in a different scenario?

You'd have to recalculate the entire tide. What the ****.

It's like saying the tides go down to 13 and up to 18. That's pretty bs. I thought tides go up and back down to initial which was 13.

They can't start at 15 and go down what the ****. Where would the rest of the compressed water go? I understand that the water can be LIFTED up to 18, but how can it start at 15 and go down to 13? So it should start at 13. And raise to 18.

@Above guy: I think they wanted 5, because the part 1 of that bit it said "the calculated mass" or something, which was 6000 which was for 5 seconds. So I used the 6000 throughout it. Physics papers are like so ****ing dumb, they're so ****. It's like a toned down version of M2 wtf and added some ****ty bits of Chemistry in.
If you think of it like a mass pulled down on a spring graph is (- cos) and the equilibirum position is halfway between the point you pull it to and the samer distace above equilibrium
15. (Original post by mir3a)
Kilowatt hour isn't even in our syllabus, and wasn't related to Newtonian world, why was it even there?
Word. I actually checked the front of my paper in panic!
16. (Original post by mir3a)
Kilowatt hour isn't even in our syllabus, and wasn't related to Newtonian world, why was it even there?
i know what a f****** joke. what is wrong with OCR?!
17. Are there going to be any solutions put up? Thaaaanks
18. Yhh i never knew They had killowatt hours in Newtonain england :L
19. (Original post by OceanFlanker)
If you think of it like a mass pulled down on a spring graph is (- cos) and the equilibirum position is halfway between the point you pull it to and the samer distace above equilibrium

It's NOT a spring though. Gravity isn't ELASTIC. What the ****.

+ to further prove my point correct.

If you PUSH the water further down, if you think of somewhere else in the world, the sea level will surely rise, so it'll average out NOT being pushed down anymore.

It's as though we're trying to say "ZOMG let's Push the water down and lift it again"

I can see how they're trying to "illustrate" an SHM question THROUGH tides. But that's not really working out?
20. Amplitude was defo: 2.5 because the highest tide was 18m and the lowest was 13m so the tide oscillated between these two values which is 5metres hence therefore amplitude was 2.5.

The radius of satellite you needed to say mv^2/r = -GMm/r rearranging cancels out the value for small m which you wernt given to leave an answer of 2.9x10^7 m.

The last question I got n to be 8.4 moles, the when the pressure was 4.5x10^5 Pa, n was = 7.25 (if i remember),
Mass = MolarMass x Number of Moles, which gives , 0.24 and 0.21 Kg the change in mass or loss of mass being 0.03Kg...

For the Helicopter mass of air, Cylinder volume = 2 x pi x r^2 x h h = speed x time, h = 60m, therefore volume approx 4200 m^3

Mass = density x volume, mass = 1.3 x 4200 = 6126 Kg or 6000Kg.

I think it was a straightforward paper, im glad i resat Electrons Photons Waves otherwise i would have defo not got the KiloWatt Hour question!!!!!!!

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