Physics Predictions/Thoughts (5 Viewers)

[Arrowshaft]

It's actually a great movie, also it goes through Ramanugans struggles with getting people to believe his work because he had no proofs. It shows his struggle to learn how to prove his formulae etc. Eventually most turned out to be correct lol.


Good luck with that lol. It's much harder than the Olympiads and most people who take it are olympians from MIT Harvard etc. Yet the average score is 1%

Have you tried it?

 

[Drdusk]

Have you tried it?

I'm a Physics major, not a math major I'll leave that type of math for the math geniuses to try. I just bother with doing Contest Physics.

As for have I looked at the questions. Yes. Do I understand how to even start proving it. Hell no .

 

[Husky]

What did you guys write for the transformer question part (a) ?

 

[Arrowshaft]

What did you guys write for the transformer question part (a) ?

Hence in accordance with conservation of energy as electrical energy is transformed into heat energy and other forms of energy. And some other stuff

 

[Husky]

Hence in accordance with conservation of energy as electrical energy is transformed into heat energy and other forms of energy. And some other stuff

Okay awesome I did the same thing was just double checking

 

[Balajanovski]

@Arrowshaft for the 9 marker, to calculate power, what did you do?
I used the inverse square law.



Rearranged to calculate for luminosity (L) which is the power output.

 

[Arrowshaft]

@Arrowshaft for the 9 marker, to calculate power, what did you do?
I used the inverse square law.



Rearranged to calculate for luminosity (L) which is the power output.

I wasted a lot of time on q33 (or whatever the circ. motion q was because i kept misreading) so I rushed that bit and said that the power was intensity times radius squared like an idiot . So i scuffed the calculations for that one as I did it last minute, other than that i talked about p-p chain and how the sun doesnt rely on the CNO cycle (accounting for only 2% of energy production) because it is not hot enough. i did the wien’s law calculation for surface temperature correctly though and then I just briefly mentioned inverse square law and the dissipation of energy spherically by 4pir^2. In retrospect it was a very easy calculation that I stupidly rushed.

 

[Arrowshaft]

So due to poor exam technique by me not reading the question properly, I think I’d lose around 5 marks for that question unfortunately

 

[Balajanovski]

I wasted a lot of time on q33 (or whatever the circ. motion q was because i kept misreading) so I rushed that bit and said that the power was intensity times radius squared like an idiot . So i scuffed the calculations for that one as I did it last minute, other than that i talked about p-p chain and how the sun doesnt rely on the CNO cycle (accounting for only 2% of energy production) because it is not hot enough. i did the wien’s law calculation for surface temperature correctly though and then I just briefly mentioned inverse square law and the dissipation of energy spherically by 4pir^2. In retrospect it was a very easy calculation that I stupidly rushed.

One thing which I'm a bit worried about is that the inverse square law is not given on the formula sheet.
Would I be penalised for using it?
Is it even valid to use it?

 

[Arrowshaft]

One thing which I'm a bit worried about is that the inverse square law is not given on the formula sheet.
Would I be penalised for using it?
Is it even valid to use it?

It is given. There is
I1r1^2 = I2r2^2

 

[Arrowshaft]

What else did you talk about for that question. I’m trying to gauge exactly how much I’d lose for that question since I rushed it

 

[Arrowshaft]

I also talked about equipartioning theorem and quantum oscillators for black bodies to explain the presence of all the wavelengths in the curve, however I just ran out of time to show that the probability for the smaller vibrational modes would be low due to higher thermal energy gaps.

Gosh I hope I don’t lose too many marks for that question.

 

[Balajanovski]

I also talked about equipartioning theorem and quantum oscillators for black bodies to explain the presence of all the wavelengths in the curve, however I just ran out of time to show that the probability for the smaller vibrational modes would be low due to higher thermal energy gaps.

Gosh I hope I don’t lose too many marks for that question.

Probably irrelevant to talk about equipartitioning theorem (this is not a theory question on Planck so why should you talk about Rayleigh-Jeans).

Here was my thought process / structure condensed:
1. Sun yellow main sequences -> proton-proton chain -> Not massive enough to provide pressure & temp for CNO cycle
2. Proton proton chain releases energy from the mass defect of the reaction -> Link Einstein's mass-energy equivalence
3. This energy is transformed into two forms. Light energy for the gamma photons released. Majority however is in the kinetic energies of the product atoms.
4. Macroscopically, the produced kinetic energy by the sun's fusion results in an increase in temperature (kinetic energy of particles relates to temp).
5. Atoms in the surface of the sun release electromagnetic energy in quantised packets E = hf from transitions between quantised thermal energy states. (Link Planck's hypothesis) Acts as a black body, irradiating away the energy it produced from fusion.
6. Sun is not a perfect black body as it is not an entirely perfect emitter. However, the sun radiates away much more light than it reflects, making the approximation valid. Furthermore, approximation of black body can be referred from intensity vs. wavelength graph of sun by its characteristic shape (given in question). It has a peak and little emission in the UV region.
7. Using approximation of sun as black body, the sun's surface temperature can be calculated via Wien's displacement law (Insert calculation).
8. Furthermore, with the data provided, the total power output of the sun (its luminosity), can be determined via the inverse square law (Insert calculation).
9. Conclusion (Which is summary of what was said)

 

[Balajanovski]

@Arrowshaft My worry about the inverse square law is that the form I used is not the form on the sheet.

 

[Arrowshaft]

Probably irrelevant to talk about equipartitioning theorem (this is not a theory question on Planck so why should you talk about Rayleigh-Jeans).

Here was my thought process / structure condensed:
1. Sun yellow main sequences -> proton-proton chain -> Not massive enough to provide pressure & temp for CNO cycle
2. Proton proton chain releases energy from the mass defect of the reaction -> Link Einstein's mass-energy equivalence
3. This energy is transformed into two forms. Light energy for the gamma photons released. Majority however is in the kinetic energies of the product atoms.
4. Macroscopically, the produced kinetic energy by the sun's fusion results in an increase in temperature (kinetic energy of particles relates to temp).
5. Atoms in the surface of the sun release electromagnetic energy in quantised packets E = hf from transitions between quantised thermal energy states. (Link Planck's hypothesis) Acts as a black body, irradiating away the energy it produced from fusion.
6. Sun is not a perfect black body as it is not an entirely perfect emitter. However, the sun radiates away much more light than it reflects, making the approximation valid. Furthermore, approximation of black body can be referred from intensity vs. wavelength graph of sun by its characteristic shape (given in question). It has a peak and little emission in the UV region.
7. Using approximation of sun as black body, the sun's surface temperature can be calculated via Wien's displacement law (Insert calculation).
8. Furthermore, with the data provided, the total power output of the sun (its luminosity), can be determined via the inverse square law (Insert calculation).
9. Conclusion (Which is summary of what was said)

Seems good, but just a correction; though equipartioning theorem was developed by Rayleigh Jean using classical thermodynamics, Planck didn’t dismiss it, in fact all he did was limit the shortest possible wavelength of the standing waves being able to be emitted and received by the walls of the cavity, thus eliminating the high probability of intensity approaching infinity toward infinitesimally small wavelengths

 

[Arrowshaft]

@Arrowshaft My worry about the inverse square law is that the form I used is not the form on the sheet.

Yeah, I don’t know tbh. They could penalise you or not dependent on the marker but I doubt it

 

[Arrowshaft]

I just didn’t have enough time to write all that stuff down. What I ended up mentioning was:
- blackbody cavity and shape of graph.
- proton proton chain and CNO cycle releasing energy through nuclear fusion. Described the net equation for the proton proton chain with positrons, gamma rays and neutrinos
- this energy is dissipated in accordance to the inverse square law, with the power output inversely proportional to the radius of the emission.
- operation of a blackbody and the nature of quantum oscillators.
- calculation, albeit wrong, for inverse square law.
- wien’s formula and surface temperature of the sun.
Again I rushed it, so couldn’t include as many points as I wanted to.
How many do you think that would get me?

 

[Balajanovski]

Gosh I hope I don’t lose too

Seems good, but just a correction; though equipartioning theorem was developed by Rayleigh Jean using classical thermodynamics, Planck didn’t dismiss it, in fact all he did was limit the shortest possible wavelength of the standing waves being able to be emitted and received by the walls of the cavity, thus eliminating the high probability of intensity approaching infinity toward infinitesimally small wavelengths

You have an excellent understanding in Planck. Sucks that you weren't able to show it.

 

[Arrowshaft]

You have an excellent understanding in Planck. Sucks that you weren't able to show it.

Poor exam technique

 

[Balajanovski]

I just didn’t have enough time to write all that stuff down. What I ended up mentioning was:
- blackbody cavity and shape of graph.
- proton proton chain and CNO cycle releasing energy through nuclear fusion. Described the net equation for the proton proton chain with positrons, gamma rays and neutrinos
- this energy is dissipated in accordance to the inverse square law, with the power output inversely proportional to the radius of the emission.
- operation of a blackbody and the nature of quantum oscillators.
- calculation, albeit wrong, for inverse square law.
- wien’s formula and surface temperature of the sun.
Again I rushed it, so couldn’t include as many points as I wanted to.
How many do you think that would get me?

Uhhh I don't know. I have terrible estimation for long responses. However, assuming that you wrote a substantial amount on each, I'd say 5-6. The main problem is it doesn't have much continuity.