Ocr A Ffe And Unifying Concepts

Scroll to see replies

I got a straight line for the half life question, and a half life of 60 hours.

I didn't think Unifying Concepts was so bad...but FFE was terrible!

Reply 21

chats

sarah12345

for the last question on ffe how would u work out the energy of the radiation? also for the first question how did u work out the final speed?

FFE was hard, last question didnt have a clue.

For speed used v=u+at

Reply 22

Asian cutie

i wasnt sure i wrote stuff about puttin the radiation in a magnetic field and measurin its deflectiion, but i dont c how that would work. im glad lots of people have got straight lines intercepting around 60.

Reply 23

chats

hopefully its 10/60 for an A in Unifying, and 25/90 in FFE

Reply 24

Asian cutie

chats

hopefully its 10/60 for an A in Unifying, and 25/90 in FFE

that would be so good. i couldnt even do some of the show questions. did anyone fet the one on fffe about showing that g=40nkg^-2? i couldnt do it

Reply 25

MrsJones

chats

hopefully its 10/60 for an A in Unifying, and 25/90 in FFE

looking at a "B" then?

Reply 26

chats

Asian cutie

that would be so good. i couldnt even do some of the show questions. did anyone fet the one on fffe about showing that g=40nkg^-2? i couldnt do it

couldnt do it

MrsJones

looking at a "B" then?

Would be more than happy with a B

Reply 27

gangstarr

guys i feel so dissapointed about that exam .. the uc was horrible - but i found FFE ok and not too bad - last question on FFE i just put how to find nature of the radiation - and that was by putting different materials in front of geiger

(ya standard aluminium ... lead and air etc)

Reply 28

simonj

For the fridge one I thought that for all the air that is cooled the same amount is heated (thats why the back of a fridge is hot - the heat is being exchanged)

Reply 29

drw25

Energy is always conserved, hence the fridge can't remove heat: all it does is take the thermal energy that's inside it and kick it out the back. If it's open, the thermal energy just goes out the back of the fridge and comes back in the front, hence the best you can expect is no net change in the temperature of the room; however, the cooling mechanism of the fridge is unlikely to be 100% efficient, so the room will get colder.

I spoke about the fire using up oxygen, and that resulting in the drop in pressure that produced the winds, rather than convection currents, which I think is a more significant effect. So I've lost marks on that one.

For the shoe, I basically said that although macroscopically, it seems the same surface is shiny and black, on a microscopic level there are different bits (that I named "shiny" particles and "black" particles) which have these properties. Again, this seems a less than ideal answer.

Got the X-ray diffraction completely wrong: I thought 0.1mm was comparable to the wavelength of an x-ray, which it isn't, so the only reason it didn't diffract was that the material surrounding the slit was transparent to X-rays.

Tension in the string was because the bob was changing its vertical velocity, so there must be an upwards acceleration hence resultant force. I wasn't sure if it was SHM or circular motion, so I didn't say either way!

I wasn't quite sure what they were asking for on the second to last part of the last question: "explain how you would experimentally find the initial activity of nuclide X". I ended up saying some rubbish about isolating it then using a Geiger-Muller tube.

All in all, not a desparately nice paper, but I think I have the marks I need - I'm well-placed because of how I did at AS and in January.

Reply 30

Asian cutie

i blabed on about convectional currents what did everyone write for the question about the forest fire

Reply 31

supersun123

wut do everyone reckon the boundry??? 40-42 for A, 35 for B, 30 for C???

Reply 32

morpheus

i didn't understand the
"explain how you would experimentally find the initial activity of nuclide X". as well

Reply 33

SamuraiJack

after doing this paper and FFE i wanted to die :frown:

Reply 34

led_zep

Both papers were tricky, not very nice overall unfortunately.

The string bob was undergoing both shm and circular motion but i think the force associated with circular motion is the one the answer was concerned with. You needed acceleration towards the centre of the circle (even though it never completes a full orbit) therefore you need a tension which is larger than the weight alone to gain a net force towards the centre.

Reply 35

apotoftea

i too found both papers hard. The synoptic was laughable.

and i also used v=u + at for the speed!

Reply 36

FlamingTelepath

I thought unifying concepts was annoying and tricky. Electricity question I think I got all wrong because of that damn generator *and* battery. We've never seen examples like that.

Forces, Fields & Energy was a piece of proverbial :biggrin:

You know the post-exam syndrome, where everyone comes out and says 'what did you put for that? oh sh*t, I forgot that equation!! etc...'? For the first time, I was the one going 'you use so-and-so equation, you fools'.

I even managed to remember that the force on an electron in an orbit is equal to a centripetal force BQV = MV²/R
Hurrah!

Reply 37

moojoo

For the electricity question, did you have to use the voltage fromt he generator as well as the emf to get the current and power of the lamps??? I got 72W but apparently thats wrong...