Howdy! Could someone please help me out with this question:
The period of revolution of the planet Saturn around the Sun is 30 times that of Earth. Determine how many times further Saturn is from the Sun than Earth.
A) 3.1
B) 5.5
C) 9.7
D) 30
The answer is C but I have not clue how they got there. The marking scheme stated the T2/r3 = 4pi2/GM formula.
-jinx_58
jinx_58
Hey jinx_58,
The marking scheme is somewhat right in using T2/r3 = 4pi2/GM because I think it uses Kepler's third law which is the ratio T2/r3 = T2/r3. To start, I am going to let:
Thus, the ratio is: TE2/rE3 = TS2/rS3. So assume the PoR of Earth is 1. So, the ratio is: 12/rE3=302/rS3 (because PoR of Saturn is 30 times of Earth). Rearranging that,
rS3/rE3=302/12
rS3/rE3=900
rS/rE = ∛900=9.65=9.7
Hope that helped. Feel free to ask any more questions.
For VCE we get to take in an A3 notes page - idk about u guys interstate tho.
Would strongly suggest putting the rearranged formulas down if you can. SAVES SO MUCH TIME.
God
Hey God,
Unfortunately I wasn't allowed to take in anything except for writing utensils, a water bottle and a calculator, according to QCAA and I believe they haven't changed that rule for this year. But I really wish we could do that.
God
Yeah, we get a formula sheet, but if we don't know how to use the formulas, we're screwed. And the formula sheet is clean and given to us with our exam paper. And it still hasn't changed from what @PhytoPlankton experienced. We can take in a clear plastic water bottle, QCAA-approved calculator and 2B pencils, blue and black pens. No whiteout or rub-out pens.
It'd be pretty awesome if we did have an A3 page of notes though. But yet again, Queensland is quite new to the whole ATAR situation.
-jinx_58
Yikes. That’s a lot painful algebra
Howdy again, I need help with solving this blackbody radiation question.
Edit: also how do we calculate stopping voltage?
Thank you,
-jinx_58
jinx_58
Hey jinx_58,
For the blackbody radiation question, you just use Wien's displacement formula which is λmax=b/T (where b=2.898x10-3). So, the answer should be T=257600K (I could be wrong tho).
As for stopping voltage, I don't think you actually need to know that for U3&4 (hence, why its not seen in the syllabus) but I believe you would use this formula: eV0= hc/λ - W to work it out.
Hope that helped.
PhytoPlankton
Thank you PhytoPlankton!
-jinx_58
Howdy again 
If anyone could explain these multiple choice questions on the 2020 Physics paper, it would be greatly appreciated:
Q 4, 8, 15, 18, 20
The link to it is below:
https://www.qcaa.qld.edu.au/downloads/senior-qce/sciences/snr_physics_20_ea_p1_mc_question.pdf
Thank you,
-jinx_58
jinx_58
Hey jinx_58,
Here are all the solutions to the above questions you wanted help with: https://imgur.com/a/GCXkeel
Hope that helps and good luck for tomorrow!
PhytoPlankton
Thank you PhytoPlankton.
However, for question 8, the QCAA answers state it was Answer C, 190m. But for paper 2, QCAA has the wrong numbers subbed in for Question 9 so it could be a QCAA mistake.
Thanks again,
-jinx_58
jinx_58
I could be wrong but I just checked the marking guide and it says its answer A for question 8 in P1 multiple choice. Let me know if I just read that wrong.
PhytoPlankton
Lol I can't read haha. Sorry about that
Also, are we supposed to know the wavelength of waves on the electromagnetic spectrum?
-jinx_58
jinx_58
Haha that's all good.
As far as I know, I don't think you need to know the wavelength of waves on the EM spectrum. If they ask you for something like that, they should give you the spectrum or that information.
Howdy (again)
I did question 19 on the 2021 Paper 1 (multi-choice) and I got A. The answers however say its B. I feel like I did it wrong but the length given is the length at rest, which L_0. You would get B as the answer if you let L (contracted length) equal 125. Moreover, doesn't the length measured by an observer at rest need to be greater than someone in a moving reference frame?
Please correct me if I'm wrong and I messed up reading the question.
Edit: Could someone also please show the working out for Q13, 8, and 4
Link to the paper is below:
https://www.qcaa.qld.edu.au/downloads/senior-qce/sciences/snr_physics_21_ea_p1_mc_question.pdf
Thank you,
-jinx_58
jinx_58
Hello again jinx_58,
So L0 is the proper length which is the length at rest which is also the length measured by the moving observer (person on the spaceship) because to the observer on the spaceship, the spaceship is at rest (just like when you're in a car). L is the contracted length which is 125m because the stationary observer will see it moving at 0.3c and thus, the length will contract for them. You can watch this Crash Course video which explains length contraction: https://www.youtube.com/watch?v=AInCqm5nCzw.
Hope that helps!
