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

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Original post by s081013
i thought lots of the values calculated were really small... that really freaked me out


Yes like the time to heat up titanium by 1680 degrees was so small?
Original post by BrokenS0ulz
Yeah I got the force as 0.066N I think and then thw acceleration was that divided by something lol. And I put second law


Yeah man same here!!
Paper was a bit harder than normal. Will post some of my calculated answers later.
Compared with June 2014 what do you guys think?

I think it was about the same, so my guess would be an A would be 40
what was with the first question, we just showed it to our teacher his response was along the lines of
(edited 8 years ago)
Lol That 1st Q though. Prove u=u² ? Lol. Was gonna right "using black magic i arrived at s=uv where v=u cause no air on moon. So therfore s=u²."

Everything in else on that Q was fine.
a) was "type of forces are not the same"
Original post by BrokenS0ulz
Did anyone get like 0.0028 seconds for the time for that titanium thing. And did anyone get 9.5Ns for the area of the Ft graph


I got like 10.5 I counted about 1367 small squares
Original post by coder4
I thought second law at first but you actually work out the force that the xenon's have and through newtons third law, the space ship must experience the same force in the opposite direction, now you do use newtons 2nd law to work it out tho :/


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.
Original post by BrokenS0ulz
Did anyone get like 0.0028 seconds for the time for that titanium thing. And did anyone get 9.5Ns for the area of the Ft graph


I got 356 seconds :s
Original post by The Room Student
Have you done M2 in maths? I used projectile motion:

Firstly resolved vertically with s = u(sinx)t + 0.5a(t)^2 and solved for t

Then resolved horizontally and subbed that into s = u(cosx)t which gave s = (u)^2(sin2x) / g


No I don't do M2. However I did get s=ucosxT but then I tried going down the phythag road and then I tried doing cos^2 + sin^2 haha no idea may of gotten 1
Original post by seizetoday
I got like 10.5 I counted about 1367 small squares


Bloody hell aha! I used 2 triangles and 2 rectangles to guesstimate it. Got 10.9 though so that's probably good news for both of us?!
Original post by seizetoday
I got like 10.5 I counted about 1367 small squares


Original post by seizetoday
I got 356 seconds :s


Oh crap :/
For the titanium thing did everyone get a really big number.


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Original post by coder4
Yes like the time to heat up titanium by 1680 degrees was so small?


yeah i thought i got it wrong! i did E= mc (delta) T and then divided it by the energy of the photon ... i think
Original post by Jim997
For question two about the space craft, did anyone get a really small acceleration? And for the law used, it was the second wasn't it?


Original post by s081013
i did mass of 1 xenon atom x number of xenon atoms x velocity of atom (impulse)/mass of space craft..and i think i got a really small value - is that what you did?

edit: for the law used, i put the law of conservation of momentum


This is what I did too, thank god! For the law, I put force equals change in momentum over/time.
The first question did throw me off a bit, but thank god I know how to do the other questions. After the F324 one yesterday, this one is like a stroll through the park ha!

For the U^2 one, I resolve to find horizontal velocity, then use v^2 = u^2 + 2as, then I work it out from there. :\ Probably got it wrong tbh, but I was running out of time.
Original post by The Room Student
Bloody hell aha! I used 2 triangles and 2 rectangles to guesstimate it. Got 10.9 though so that's probably good news for both of us?!


haha maybe i think they may have a big range because it was an odd shape
Original post by coder4
I thought second law at first but you actually work out the force that the xenon's have and through newtons third law, the space ship must experience the same force in the opposite direction, now you do use newtons 2nd law to work it out tho :/


Yeah this is exactly what I was thinking, you use both! You can't use the 2nd to solve unless you understand the 3rd. But it asked which you use to solve so I think it wanted the second because it's more directly related? Completely understand what you're saying though, sh** questions imo
For the last pressure question did anyone get 1.5 x 10^7?
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 somehow ace the 4th unit - This was supposed to be my best unit! :angry:
(edited 8 years ago)
Original post by seizetoday
I got like 10.5 I counted about 1367 small squares


I got 10.8. I counted the number of big square than times it by the (200 N x 1x10^-3)

For the titanium thing, I think I got a very small value too. Definitely lower than 1 second.

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