PHYA5 ~ 20th June 2013 ~ A2 Physics

Reply 1440

AWithers95

Original post by mrwho

I thought it was gamma rays, emitted in discrete packets when the nuclei return to their ground states.

I wrote that, but I had no idea if that was actually true or not.. :wink:

Reply 1441

Infinity1

Applied physics (5C)

what did people write for why fuel is injected early?

i said it was so that the fuel could mix with the oxygen to get more complete combustion, but was pure guess work

Reply 1442

mrwho

Original post by Jam Jam24

Whats the deifiniton of an atomic mass unit? We weren't taught about it. I just put the mass of a proton, which equates to 1.67x10^-27 but had no idea!!

We weren't taught it either. Sorry to tell you though, but the Atomic Mass Unit is u (the thing you multiply by for mass defects), which is 1.661*10^something, not the mass of a proton. I had no idea how to define it; if I'm extremely my poorly explained mathematical definition will get the marks, but I highly doubt it.

We also weren't taught what happens to the neutrons in a moderator when they are colliding elastically. Can't even remember reading about that in the book. Oh well.

Reply 1443

George_

2

Original post by Snedss

put 15 and B+ decay which i think could be wrong
Got 8.4 for temp of water
0.016kg for mass of ice
around 130 mol for first amount of gas
3.5 mol for when its open
size of lense was 46cm (meant to about 50 so seemed right)
age of universe got 14.1b
about all i can remember

It asked for the mass when it was open, not the number of moles. I got something like 0.17kg.

I also got 46cm, 0.017kg of ice (your is right, I was just using Q=ml instead of both), and 8.51 for the temp of cola.

Reply 1444

Snedss

1

Original post by mrwho

I thought it was gamma rays, emitted in discrete packets when the nuclei return to their ground states.

I also put that, also related it to e=hf

Reply 1445

Pinkhead

14

Original post by blahblahh

I put that they release photons which is gamma radiation ?
And i put that debrolgies hypothesis is that if waves can have particle like nature then particles can have wave like nature ?

Anyone know if this is right ?

It's to do with wave particle duality so if you mentioned matter particles exhibiting wave properties like diffraction, you'd get at least 1 mark.

Reply 1446

Snedss

1

Original post by George_

It asked for the mass when it was open, not the number of moles. I got something like 0.17kg.

I also got 46cm, 0.017kg of ice (your is right, I was just using Q=ml instead of both), and 8.51 for the temp of cola.

ahh, yes, i did convert it to moles which got around 3.3?

Reply 1447

mrwho

Original post by Infinity1

Applied physics (5C)

what did people write for why fuel is injected early?

i said it was so that the fuel could mix with the oxygen to get more complete combustion, but was pure guess work

That's what I said too. It seems like the most logical answer, doesn't it?

Reply 1448

AWithers95

Original post by George_

It asked for the mass when it was open, not the number of moles. I got something like 0.17kg.

I also got 46cm, 0.017kg of ice (your is right, I was just using Q=ml instead of both), and 8.51 for the temp of cola.

I got 8.4 as the temperature and 0.016kg - probably rounding differences in here.

Reply 1449

bugsuper

8

Original post by mrwho

We weren't taught it either. Sorry to tell you though, but the Atomic Mass Unit is u (the thing you multiply by for mass defects), which is 1.661*10^something, not the mass of a proton. I had no idea how to define it; if I'm extremely my poorly explained mathematical definition will get the marks, but I highly doubt it.

We also weren't taught what happens to the neutrons in a moderator when they are colliding elastically. Can't even remember reading about that in the book. Oh well.

An atomic mass unit is 1/12th the mass of a nucleus of carbon-12 - pretty sure that's the official definition

Reply 1450

mrwho

Original post by bugsuper

An atomic mass unit is 1/12th the mass of a nucleus of carbon-12 - pretty sure that's the official definition

If only I'd know that before! I actually wrote something about carbon 12, but then I thought that was related to Avogradro's constant instead and crossed it out. Oh well.

Reply 1451

Dslash

Atomic mass unit from the book: "1/12th of the mass of an atom of the carbon isotope C-12."

Feel happy that I would never have thought of that

Reply 1452

Jam Jam24

8

On the first question did anyone put : A hydrogen atom/ Proton?

on the equation cos it said a proton is relased. A positron or an electon couldn't work cos the masses didnt add up

(edited 10 years ago)

Reply 1453

grimly

After this exam i think i will get a low overall grade <D. There goes my uni place because of one exam, any ideas what i can start looking for now seeing as i will probably not get a place anywhere for engineering?

Reply 1454

Snedss

1

Original post by mrwho

If only I'd know that before! I actually wrote something about carbon 12, but then I thought that was related to Avogradro's constant instead and crossed it out. Oh well.

http://en.wikipedia.org/wiki/Atomic_mass_unit
Third line, i also wrote 1/12 the mass of a atom on C12

Reply 1455

grimly

After this exam i think i will get a low overall grade <D. There goes my uni place because of one exam, any ideas what i can start looking for now seeing as i will probably not get a place anywhere for engineering?