***2015 LC Physics - June 15th***

The_N4sir

Lovely paper. Section A was very nice as was Section B. Managed to do an extra question aswell. Hopefully that is an A in the bag

Troxck

That went terribly for me. I did worse than I did in the mocks, I really wanted a high B or even an A but after that, a C is more likely (if even that).

A change of the CAO is in order now

Jammysticks

Tin-whistle length was .579 divided by 2, wasn't it?

2345

Jammysticks wrote: »

Tin-whistle length was .579 divided by 2, wasn't it?

Yep 28.5 cm

Chickennuggets

Section a was easy , section b was terrible , was hoping for an A1 . A bit more like a low B or a high C now

Jammysticks

SI unit of temperature is Kelvin, not degrees C?

And frequency of string is increased by 1.5 times when tension changes from 36N to 81N?

2345

Jammysticks wrote: »

SI unit of temperature is Kelvin, not degrees C?

And frequency of string is increased by 1.5 times when tension changes from 36N to 81N?

yeah thats what i got.
What about why a pipe at open at only one end has half the harmonics?

qweerty

In case anyone's interested: news report.

Benm123

Hopefully I'm not the only one that the polystyrene cup threw! I included it in the equation with SHC 1, no idea why, was sure they had an error in paper with not giving it's shc! Silly me, do you think I'll lose many marks for it? Like I didn't include it in the assumption and then had the error in the calculations, everything went grand I'm sect A but I'm worried that'll take me down a good chunk!

anera

how did it go for everyone??

Jammysticks

2345 wrote: »

yeah thats what i got.
What about why a pipe at open at only one end has half the harmonics?

Just draw the diagrams for the first and second harmonics of open and closed pipes, which show that closed pipes produce odd harmonics while open pipes produce all harmonics.

Barry1000

WE NEED A UV LIGHT #physicsbanter

The_N4sir

Benm123 wrote: »

Hopefully I'm not the only one that the polystyrene cup threw! I included it in the equation with SHC 1, no idea why, was sure they had an error in paper with not giving it's shc! Silly me, do you think I'll lose many marks for it? Like I didn't include it in the assumption and then had the error in the calculations, everything went grand I'm sect A but I'm worried that'll take me down a good chunk!

It threw me off aswell but I assumed no heat was transferred to the cup from the water since there was no SHC given. I got close to the value of SLHV so should be okay hopefully

Guys you all probably did better than you think aswell

Jammysticks

In the experiments question 4, what was the circuit diagram that had to be drawn?

And are 2 other leptons the Tau and the Muon? neutrino is subject to the strong n. force?

OMGeary

Didn't like the paper, was very different

2345

Jammysticks wrote: »

In the experiments question 4, what was the circuit diagram that had to be drawn?

And are 2 other leptons the Tau and the Muon? neutrino is subject to the strong n. force?

yep tau and muon that was in the tables

AMDD

Jammysticks wrote: »

In the experiments question 4, what was the circuit diagram that had to be drawn?

And are 2 other leptons the Tau and the Muon? neutrino is subject to the strong n. force?

Pretty sure there's a page in the table that gives examples of Leptons. Tau and the muon are included in this list.

3w4

What did people get for the velocity of an electron and what was the minimum wavelength of the x-ray?

blue_velvet

3w4 wrote: »

What did people get for the velocity of an electron and what was the minimum wavelength of the x-ray?

for velocity I got one point something ×10^8 by using formula QV=1/2mv^2 . And for wavelength I think it was something ×10^-11 and I used hf=1/2mv^2 to get f and then subbed f into c=f×wavelength to get wavelength

SteveZissou

For the particle physics, did anyone get an energy value of around 0.87MeV?

Chickennuggets

SteveZissou wrote: »

For the particle physics, did anyone get an energy value of around 0.87MeV?

I got .79Mev

What did people. Get for the latent heat of vaporisation in q 2 ?

2345

anyone get 2x10^7 m for radius in Q6

Chickennuggets wrote: »

What did people. Get for the latent heat of vaporisation in q 2 ?

it is meant to be 2.3x10^6 from book

Chickennuggets

For Q1 Boyle law what was the pressure at 250 cm ? I got something like 105 kpa

Fiona G

very sly mixing in electromagnetism with particle physics...

Chickennuggets wrote:

For Q1 Boyle law what was the pressure at 250 cm ? I got something like 105 kpa

I think I got 106 kPa, same ball park

Chocolalla

For heat question what's the equation and sub ins ?

AMDD

Chocolalla wrote: »

For heat question what's the equation and sub ins ?

Heat Lost = Heat Gained
MC(change in temp) steam + ML for steam = MC(change in temp) water + MC(change in temp)cup
I neglected the cup as I said c for it is =0.

Chocolalla

AMDD wrote: »

Heat Lost = Heat Gained
MC(change in temp) steam + ML for steam = MC(change in temp) water + MC(change in temp)cupt
I neglected the cup as I said c for it is =0.

Ok I got the equation but I was contemplating what to write for capacity of polystyrene cup

AMDD

Chocolalla wrote: »

Ok I got the equation but I was contemplating what to write for capacity of polystyrene cup

I'm almost sure you'll get the marks if you state in the assumptions that the student assumed the specific heat capacity was x.

Chickennuggets

What was the answer for q5 (a)

AMDD

Chickennuggets wrote: »

What was the answer for q5 (a)

I did 41cos30 x 3

Benm123

Chickennuggets wrote: »

I got .79Mev

I also got an answer like that but then went back and realised I forgot to sqaure the speed of light! I them re did it and squared the speed of like and got 511MeV which seemed like a much nicer answer

Chocolalla

Anyone do question eleven?

AMDD

Chocolalla wrote: »

Anyone do question eleven?

Yep

Chocolalla

AMDD wrote: »

Yep

Lol Answers pls

blue_velvet

Chocolalla wrote: »

Anyone do question eleven?

I did! How did you define the Tesla?

AMDD

Chocolalla wrote: »

Lol Answers pls

(a) Tesla I wasn't too sure. I just used the formula saying it's the ratio of the work function to the area.
(b) A.C I believe is a sin wave and D.C I believe is the same except you don't include beneath 0.
(c) Electromagnetic induction I said is when an EMF is induced due to the change in magnetic field linking a circuit.
(d) I believe this is to do with inducing an EMF which D.C wouldn't do. Wasn't too sure on this.
(e) I said with low voltage this means there's a smaller current according to Ohm's Law which means there is less charge per second.
(f) Subbed into formula
(g) Just said A.C is constantly changing so you need an RMS value to compare.
(h) Advantage: Environmentally friendly
Disadvantage: Expensive

Looking back, I actually think I answered this question pretty badly, haha, at least it was an extra question.

Chocolalla

AMDD wrote: »

(a) Tesla I wasn't too sure. I just used the formula saying it's the ratio of the work function to the area.
(b) A.C I believe is a sin wave and D.C I believe is the same except you don't include beneath 0.
(c) Electromagnetic induction I said is when an EMF is induced due to the change in magnetic field linking a circuit.
(d) I believe this is to do with inducing an EMF which D.C wouldn't do. Wasn't too sure on this.
(e) I said with low voltage this means there's a smaller current according to Ohm's Law which means there is less charge per second.
(f) Subbed into formula
(g) Just said A.C is constantly changing so you need an RMS value to compare.
(h) Advantage: Environmentally friendly
Disadvantage: Expensive

Looking back, I actually think I answered this question pretty badly, haha, at least it was an extra question.

No I think your answers are good , for tealsa since it said magnetic flux I just gave the def I don't think I'm right thou

Chocolalla

blue_velvet wrote: »

I did! How did you define the Tesla?

I just gave the def for magnetic flux, u?

blue_velvet

AMDD wrote: »

(a) Tesla I wasn't too sure. I just used the formula saying it's the ratio of the work function to the area.
(b) A.C I believe is a sin wave and D.C I believe is the same except you don't include beneath 0.
(c) Electromagnetic induction I said is when an EMF is induced due to the change in magnetic field linking a circuit.
(d) I believe this is to do with inducing an EMF which D.C wouldn't do. Wasn't too sure on this.
(e) I said with low voltage this means there's a smaller current according to Ohm's Law which means there is less charge per second.
(f) Subbed into formula
(g) Just said A.C is constantly changing so you need an RMS value to compare.
(h) Advantage: Environmentally friendly
Disadvantage: Expensive

Looking back, I actually think I answered this question pretty badly, haha, at least it was an extra question.

for (e) I said low voltage means larger current which leads to greater power loss and then I explained with reference to Joule's Law P=I^2R and P=VI

AMDD

Chocolalla wrote: »

No I think your answers are good , for tealsa since it said magnetic flux I just gave the def I don't think I'm right thou

I think I may have snuck in the definition for that also since I just decided to write all that I knew, don't think they will mark me down for having extra, even if it isn't right.

AMDD

blue_velvet wrote: »

for (e) I said low voltage means larger current which leads to greater power loss and then I explained with reference to Joule's Law P=I^2R and P=VI

Hmm, that sounds better, I thought I should have fit in Joule's Law in there somewhere.

SteveZissou

Chickennuggets wrote: »

I got .79Mev

Actually I think I got that as well, couldn't remember! Thanks:)

blue_velvet

AMDD wrote: »

Hmm, that sounds better, I thought I should have fit in Joule's Law in there somewhere.

I was unsure as to whether to make reference to the written text above in some of my answers or not??

AMDD

blue_velvet wrote: »

I was unsure as to whether to make reference to the written text above in some of my answers or not??

Oh ****, I just realised that I didn't even look at that, that's so dodge haha.

Chickennuggets

Benm123 wrote: »

I also got an answer like that but then went back and realised I forgot to sqaure the speed of light! I them re did it and squared the speed of like and got 511MeV which seemed like a much nicer answer

Im 90% I squared the speed

blue_velvet

Chocolalla wrote: »

I just gave the def for magnetic flux, u?

Is Tesla not the unit for magnetic flux density? I said magnetic flux÷Area=magnetic flux density and then drew a diagram showing area and magnetic field lines..I think I said something about the magnetic flux density being the number of magnetic field lines falling perpendicularly??

Benm123

Chickennuggets wrote: »

Im 90% I squared the speed

Hmm.. This is confusing me.
I did
E=Mc^2
Taking m as mass of electron
And c as speed of light
Then put my value for over eV.

I got 510.99 MeV then which rounded to a nice 511, which seemed like a more suitable answer than them asking for mega electron volts and then having a 0.something answer.
But I'm doubting myself now that others have said they also got 0.something MeV

Also, coming out of the exam my friend who usually gets A1's said he got 0.something but then I asked did he square the speed of light and he said ohhhh **** no he didn't.
What did anyone else get?

blue_velvet

For the resistance of a metallic conductor experiement what did people say was the rate of change of resistance?was it just the slope?

AMDD

blue_velvet wrote: »

For the resistance of a metallic conductor experiement what did people say was the rate of change of resistance?was it just the slope?

Didn't do it but pretty sure that's right.

uzpuz

I put in 4180 for specific heat capacity for polystyrene but I knew it was wrong.
However I ended up getting 2.3 by 10 to power 6 which is the latent heat of vaporisation as stated in previous marking schemes

Chocolalla

blue_velvet wrote: »

Is Tesla not the unit for magnetic flux density? I said magnetic flux÷Area=magnetic flux density and then drew a diagram showing area and magnetic field lines..I think I said something about the magnetic flux density being the number of magnetic field lines falling perpendicularly??

I just thought of the magnetic flux def which is magnetic flux density by area i think will get attempt marks hopefully

uzpuz wrote: »

I put in 4180 for specific heat capacity for polystyrene but I knew it was wrong.
However I ended up getting 2.3 by 10 to power 6 which is the latent heat of vaporisation as stated in previous marking schemes

I think I did that as well