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OCR Physics A G484 - The Newtonian World - 11th June 2015

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Original post by seizetoday
I got like 10.5 I counted about 1367 small squares


I got 11 for the area underneath the graph as an estimate. So I think a range should be expected?
Original post by Help_Me_Alex
For the last pressure question did anyone get 1.5 x 10^7?


yup
Original post by Help_Me_Alex
For the last pressure question did anyone get 1.5 x 10^7?


I think so

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Original post by seizetoday
I got like 10.5 I counted about 1367 small squares


I got 11 but counted big squares then 1/2 big squares then 1/4 big squares. do you reckon I'll be in the accepted range?
Original post by Help_Me_Alex
For the last pressure question did anyone get 1.5 x 10^7?

YES!
Original post by a123a
I got 11 for the area underneath the graph as an estimate. So I think a range should be expected?


Yeah I imagine they'll accept anything from like 9-11 Ns


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Original post by seizetoday
yup


Yeah !
Guys, i feel like crying... I thought I was so ready for this exam until I saw the first question . At least it wasn't as bad as F324.
There will deffo be a range for that obscure shape
Original post by Flux_Dubstep


for the volume used in the calculation, did you use the volume of both parts of the container (sorry i can't remember what the parts are called) or just the bigger part?

gosh i'm so sorry i know this is really vague :P hope you get what i mean
to work out the acceleration of the spacecraft do (mass of xenon)x(speed of xenon)/(mass of spacecraft - mass of xenon)
Original post by Ki Yung Na
Rocket xenon ions question - I put second law but for the calculation itself I just put **** loads of things down in the hope of some method marks. It was do to with momentum and impulse right? Ofc with newtons second law.

The intricacies of this exam was my downfall.
Now a B for physics looks far off even if I ace the 4th unit - This was supposed to be my best unit! :angry:


I did the same, I wrote Newton's 2nd Law but I did the calculation by dimensional analysis to get the answer's units as ms^-2.
Original post by Help_Me_Alex
For the last pressure question did anyone get 1.5 x 10^7?


Yes! I nearly forgot to add the volumes... that's comforting!
I got 5.1 for the area... FML.
Original post by Lucy.Parker.
Guys, i feel like crying... I thought I was so ready for this exam until I saw the first question . At least it wasn't as bad as F324.


I think this was what OCR tried to do, by putting the most challenging question 1st for throw people off. I'm sure you did fine
How did the acceleration change if the engine was left running?
Original post by The Room Student
Yeah that was my dilemma... I'd used 2nd Law and 3rd Law!

I went for 3rd Law after deliberating it. Rocket physics is a common example of it. Not sure though.


Ohh i went for the conservation of momentum thing but thinking about it yeah newtons 3rd law is probably right
didnt they ask for the change in velocity on this question? i got 11/180 as the change in velocity 11Ns for area under graph
Original post by Red Fox
How did the acceleration change if the engine was left running?


I said it would increase because the mass of the spacecraft will be decreasing because the ions are being emitted


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Original post by Red Fox
I did the same, I wrote Newton's 2nd Law but I did the calculation by dimensional analysis to get the answer's units as ms^-2.


I was in the process of unit analysis too but I stopped myself each time I tried thinking I would be missing stuff, I did think things would cancel but I just sort of thought "meh" and did the other stuff I was missing :/

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