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OCR Physics A Breadth of Physics (24th May 2016) Discussion

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Original post by Rectum_resizer
Pretty sure it was momentum time graph because the gradient was Ft, which is change in momentum(impulse), so a momentum time graph would have the same gradient.



Correct that's what I did
Density was 7500 and I said acceleration since f=ma
not it was 750


Well I forgot to do it myself because I spent so much time trying to figure out the units for u^2/m^2s^-2 cos I'm stoopid.
Did anyone get 16 for elastic potential ratio?
Original post by sddsfsdafs
not it was 750


So metal is less dense than water?
you forgot to divide the mass my 9.81, lots of people got 750 buddy
Original post by Oooskar
For the multiple choice potential divider question can someone explain how this method is wrong? The pd across the resistor in parallel with the circuit AB is 9*(3000/4000)=6.75V (emf=9V, this resistor=3000 ohms, other resistor=1000 ohms). The current in the circuit AB is 1mA so the power in the circuit AB is P=IV=6.75mW, I ended up putting 6mW which apparently is the correct answer anyway but I would just like to know where the flaw is in my method.

Posted from TSR Mobile


They gave you the current going into the first resistor (1000ohm), 3mA, so the voltage across it was 3x10^-3*1000=3v, so the voltage across the second resistor was 6v. so the second circuit had a voltage of 6v and a current of 1mA (given), so 6 *1x10^-3 is 6mW. ratio method doesn't work in this case, no idea why
Original post by Parhomus
Density was 7500 and I said acceleration since f=ma


Yh i got 7500 too

I did like this:
9-7.8 = 1.2
1.2 is upthrust

Upthrust = Volume of water * density of water * 9.81

Rearrange to find volume of water

Volume of water = volume of cylinder
Mass of cylinder = 9 / 9.81
Therefore density = mass/volume
= 7500
Original post by sddsfsdafs
Did anyone get 16 for elastic potential ratio?


Think so
Original post by viktorh
I used the weight of the cylinder/9.81=mass of the cyclinder

then I took the difference between the two newton meter readings = the upthrust on the cylider = Apgh

deduced h from that. Used H and A to find the volume

Mass/Volume = density.

Anyone else do it like this? answer I got was around 750


What question no. was this?
Original post by sddsfsdafs
Did anyone get 16 for elastic potential ratio?


i got 0.2/0.8=0.25 :s-smilie:
Something like 1.3 x10^-4 I think.
Original post by viktorh
got 6.8 m/s for the speed of the carbon atom after the collision with the hydrogen atom. Seemed a little small to me but the carbon atom is massive in comparison so Im hoping that's right


I got 78.2 m/s
Original post by rafiuddin
i got 0.2/0.8=0.25 :s-smilie:


I got that but now I'm starting to doubt it because it seemed too easy
Original post by suhaylpatel786
Yh i got 7500 too

I did like this:
9-7.8 = 1.2
1.2 is upthrust

Upthrust = Volume of water * density of water * 9.81

Rearrange to find volume of water

Volume of water = volume of cylinder
Mass of cylinder = 9 / 9.81
Therefore density = mass/volume
= 7500


I just used the fact that upthrust=weight of water displaced but yeah same working pretty much.
do you think that depth will be as hard as todays paper?
Original post by WhizzKidhehe:)
I got 78.2 m/s


I got 79.1
(edited 7 years ago)
Reply 299
how did did you do the density question can someone explain please?

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