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

FummyJr
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#1401
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#1401
(Original post by a123a)
I got all of these except the last one? I added the volumes and uses the previous pressure and volume of the He cylinder and did P1V1=P2V2. Is that method correct?
PV = PV only works for a fixed mass of gas. You had to work out the total number of moles (45 of air + 41 of He) = 86 mol
And then work out the total volume, by adding the 2 volumes, I can't remember what that was. Then you used pv=nRT with T=293 those values to get the pressure. which was 1.5x10^5
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seizetoday
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(Original post by Oraeng)
What did people put for the describe the acceleration from the force/time graph? Got so confused
I asked this question yesterday.
I wrote acceleration increased at a constant rate upto 3 secs
then increased non uniformly to 6 secs
then acceleration decreased to 10 sec
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zXx AJL xXz
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#1403
How were we supposed to know the first question?!!
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Shabz12357876877
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fummy jr i did everything but add the volume how many marks do i get?
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gothmog827
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(Original post by Elcor)
Some answers I got:

Ion mass = 2.18x10 ^-25
Initial acc = 1.27x10^-5
Satellite velocity =0.061
Star mass = 1.97x10^30
Time was something in millisecond
Pressure = 1.5x10^7
I think I agree with all that, for SHM I got 1.79x10^-3 and 4.52
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BrokenS0ulz
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(Original post by alanconnel)
For the one about show s=u2
i ended up with something like s= -2u^2sin(theta)cos(theta)/t ??
acceleration is increasing at a constant rate, then acceleration was decreasing at a decreasing rate, then deceleration was increasing at an increasing rate. something like that?

For that big geaph did u guys basically do resonance, with the resonant frequency at 8Hz? Also when we had to draw the new v/t graph, did you just draw a steadily decreasing amplitude version of the curve already drawn on?
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a123a
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Ok I know I dropped a mark on the s is proportional to u^2.
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George_C_Slack
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#1408
For that last Q i got like 1.68x10^6pa and i seems like it was 1.5x10^6 dyou think this could be due to rounding error or have i gone wrong ?
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kate8
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#1409
Did I miss out a page or was there no circular motion? Panicking now!

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SH0405
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(Original post by Help_Me_Alex)
For the last pressure question did anyone get 1.5 x 10^7?
Yep. Almost certainly correct.
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Elcor
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(Original post by FummyJr)
PV = PV only works for a fixed mass of gas. You had to work out the total number of moles (45 of air + 41 of He) = 86 mol
And then work out the total volume, by adding the 2 volumes, I can't remember what that was. Then you used pv=nRT with T=293 those values to get the pressure. which was 1.5x10^5
10^7 actually

I wrote my answer wrong

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MathsAddict
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(Original post by fatart123)
For the oscillating object that has its frequency slowly increased, does the amplitude remain the same and the only change as f increases it that the graph gets squashed together?
yeah graph squashed together as number of oscillation per unit time increased which is frequency that would be correct.
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FummyJr
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(Original post by alanconnel)
For the one about show s=u2
i ended up with something like s= -2u^2sin(theta)cos(theta)/t ??
I got s = -(2sinθcosθ)u^2/a
So s=u^2 x -(2sinθcosθ)/a
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BrokenS0ulz
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#1414
(Original post by gothmog827)
I think I agree with all that, for SHM I got 1.79x10^-3 and 4.52
I got that!
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ImLiterally12
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(Original post by MathsAddict)
it was silly to count boxes typical of ocr tbh at least let us intergrate or something to find impulse.
I agree that having to count boxes is silly, I realise that's what they wanted us to do but i just used a trapezium to estimate the area. It would have taken me a fair bit of time to count every box and I nearly ran out of time as it is.
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a123a
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(Original post by FummyJr)
PV = PV only works for a fixed mass of gas. You had to work out the total number of moles (45 of air + 41 of He) = 86 mol
And then work out the total volume, by adding the 2 volumes, I can't remember what that was. Then you used pv=nRT with T=293 those values to get the pressure. which was 1.5x10^5
Oh ok. So I've lost three marks there. But I did add the volumes, do you see that getting a mark?
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rabirabbit
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#1417
That moment you realise you talked about air resistance on the space ship in space... :facepalm:
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Pholl
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#1418
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#1418
For the last pressure question, did anyone else think that because it mentioned earlier in the question that a new molecule was "formed", the number of moles doesn't change? Went into chemistry mode for that one...
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alanconnel
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(Original post by FummyJr)
I got s = -(2sinθcosθ)u^2/a
So s=u^2 x -(2sinθcosθ)/a
oh yeah i think i got that but for a i put 9.81
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gothmog827
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first graph: negative constant gradient through origin
second: still sinusoidal but decrease in amplitude and slight increase in time period (not sure if this second point is necessary)
third: basic resonance graph, with peak at 8Hz
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