OCR Physics B G495 Field and Particle Pictures June 21st 2011 Exam Thread

If the bar bent - then wouldn't one side's length be shortened and one side's length be longer due to relative extension - that's what i put :s

That's what I said - the bottom part would be longer as it would be under tension, and the top would be shorter as it would be under compression.

Reply 961

Summerdays

10

Original post by rggregrgr

That's what I said - the bottom part would be longer as it would be under tension, and the top would be shorter as it would be under compression.

The overall length has shortened, but yes, the top would be under compression and the bottom would be under tension. That's what I said.

Reply 962

foxymoron

Original post by Summerdays

The overall length has shortened, but yes, the top would be under compression and the bottom would be under tension. That's what I said.

The point is that the length would be different depending on which side you measured - length variation would increase.

Reply 963

Summerdays

10

Original post by foxymoron

The point is that the length would be different depending on which side you measured - length variation would increase.

Hmm... the section C practice paper I did pretty much said what I wrote - but you could be right, actually. I didn't really have enough time to fully think about it.

Reply 964

5liam5

Original post by Summerdays

Hmm... the section C practice paper I did pretty much said what I wrote - but you could be right, actually. I didn't really have enough time to fully think about it.

Didn't the practice paper say it got shorter?

I think if you're measuring the along the metal what you're saying is true but if you're measuring just from one point to straight across to the other, the bar is getting shorter either way. Like if you bend a ruler the points are always going to get closer together.

Reply 965

Summerdays

10

Original post by 5liam5

Didn't the practice paper say it got shorter?

Yep, and that's what I wrote.

Reply 966

Pegasus2

16

Terrible exam, worst one i've taken at college. I din't prepare properly for it, also got a rather shallow sleep that night. Things I knew about I could not recall which was quite frustrating. Missed out quite a few marks reading from this thread on things I knew about arg! The magnetic field/electron spiral question, I said that the electrons velocity decreases and thats why the spiral increases. For the first part I even wrote the equasion r=mv/bq but it did not occur to me to say the field was working at right angles.

Reply 967

Summerdays

10

Let's hope for low grade boundaries :redface:

Reply 968

shadow12345

3

has any one uploaded the paper yet?

Reply 969

mr_spurfect

How many marks do you reckon I'll need for 50 UMS?

Reply 970

nth1992

Original post by Harry-AA

I got 5kg for for the mass or uranium :/ must have put it into my calculator wrong or something

i got 5kg too. i was pretty confident with my ans, cause 1000kg seems a lot. i dont think we have to x235 cause everything was per mole, not per nuclei

Reply 971

ChicharitoH

Original post by nth1992

i got 5kg too. i was pretty confident with my ans, cause 1000kg seems a lot. i dont think we have to x235 cause everything was per mole, not per nuclei

The way you gotta look at it is like this:

They gave you the Power and you know Power is Energy / Time so to get energy you times the power by the seconds in a year. This is the Total Energy

You also know the energy per fission from the previous querstion. So to get the number of fissions you divide the Total Energy by the Energy per fission.

The number of fissions is also equivalent to the number of U235 nuclei used so you now know the number of U235 nuclei.

They also gave you the value of 1 u which is about 1.7 x 10^-27 kg but in U235 there are 235 u. So the mass of one nuclei is 235(1.7 x 10^-27) kg

So to get the total mass you have to times the number of nuclei by the mass of one nuclei and this comes out to be about 1100 kg.

Hope this helps. :smile:

Reply 972

Jodin

2

Does anyone recall if there were any questions on fundamental particles or the like? Seems odd for them to not touch upon them even slightly and I can't recall anything relating to it, all I remember is the first question concerning some very basic properties.

Reply 973

tyyger

1

Original post by Summerdays

I pretty much said the same thing. For the last one I aid that the bar is more likely to sag under its own weight, and thu the length would tend to decrease.

If it sags under it's own weight, but still has to reach the two markers, surely the bar would have to longer, to reach them. As it's had more distance to cover,
that's what i put :s-smilie:

Reply 974

arianex

9

Original post by Jodin

Does anyone recall if there were any questions on fundamental particles or the like? Seems odd for them to not touch upon them even slightly and I can't recall anything relating to it, all I remember is the first question concerning some very basic properties.

Well, there was that Q at the start asking us to identify the fundamental particles that had the properties they were looking for - but in any case, you're right - there weren't that many Qs about fundamental particles themselves...though they did cover the whole binding energy+fission/fusion thing.

Reply 975

Summerdays

10

Original post by arianex

Well, there was that Q at the start asking us to identify the fundamental particles that had the properties they were looking for - but in any case, you're right - there weren't that many Qs about fundamental particles themselves...though they did cover the whole binding energy+fission/fusion thing.

I don't even remember that question :tongue:

Reply 976

Helsy

12

Hey everyone!! I just wondered how everyone did in the end.... I got an A overall in the A level, and I managed an A in the June exam.

Hope you've all got what you wanted/needed!! :smile:

Reply 977

Jodin

2

Yo, got an A in the end, was 3 marks off the A* which is a bit of a bugger (and the marks look suspicious to me!), but I'm into Warwick so no worries.