HSC Physics Question Thread

[jamonwindeyer]

My teacher didn't specify, he won't even give us any hints haha.
So far my class has only done Motors/Generators, Ideas and Quanta. However my teacher did say that the prac will be on something we haven't done yet

Considering the entire class will need to do it I'm guessing it will have to involve a prac where alot of people can take part in it. So circuits? Motion pracs involving weights and retort stands?

Rats! Very strange - It could even be a Space prac with formulas given! You might be getting the pendulum experiment

In any case, try and read up on the following:

- The theory, if you can, but for you this is difficult because no hints!
- Accuracy, validity, reliability
- Variables (independent, dependent, controlled)
- Graphing and lines of best fit
- Discussions (what to include, how it is structured, etc)

There's not much else you can do unfortunately, especially with so little to go on! It might be worth seeing if there are any prac exams on THSC that you can use as a guide

[Maraos]

Rats! Very strange - It could even be a Space prac with formulas given! You might be getting the pendulum experiment

In any case, try and read up on the following:

- The theory, if you can, but for you this is difficult because no hints!
- Accuracy, validity, reliability
- Variables (independent, dependent, controlled)
- Graphing and lines of best fit
- Discussions (what to include, how it is structured, etc)

There's not much else you can do unfortunately, especially with so little to go on! It might be worth seeing if there are any prac exams on THSC that you can use as a guide

Thanks for the advice and quick reply!

I'll check out that site, also I'll see if i can squeeze anything out of my teacher this week haha

[johnk21]

Can someone please explain to me what Planck and Einsteins contribution are to the black body radiation curve? Thanks in advance

[winstondarmawan]

Hello!
1. Can someone please explain Pauli's exclusion principle and electron's quantum numbers clearly? We went over it but I don't really understand it properly.
2. What are the things to look out for and include in a Prac Exam discussion? I lost many marks there and I'd like to avoid it in the future.
TIA

[jamonwindeyer]

Can someone please explain to me what Planck and Einsteins contribution are to the black body radiation curve? Thanks in advance

Hey John! I've written a couple of guides that cover this general topic area, see them here and here Hope they help!

[Maraos]

Hi!
I've got a question regarding the Pendulum experiment (when you are altering the mass to determine the acceleration due to gravity).

How would you improve the validity of this experiment?

My solution would be to ensure that the controlled variables are kept constant (even more constant then what they currently are).
ie: using a digital measuring gauge to ensure that the angular displacement (theta) of the pendulum is kept constant (as opposed to using a protractor which would increase the chances of human reading error).

Would this answer be fine? Also what else what you include to improve the validity of this particular experiment? And is my understanding of validity even correct? 

Any help would be greatly appreciated 

Thanks 

[beau77bro]

Hello!
1. Can someone please explain Pauli's exclusion principle and electron's quantum numbers clearly? We went over it but I don't really understand it properly.
2. What are the things to look out for and include in a Prac Exam discussion? I lost many marks there and I'd like to avoid it in the future.
TIA

Is this in ideas for superconductors? If so this is very very far from what you need to know. From what I understand of it- two electrons can't spin in the same state inside a quantum system - cooper pairs don't follow this and spin in the same state. This along with the lattice structure vibrating so little at the critical temperatures means these pairs can form. - I think. Quantum numbers I do not know and I look forward to a better explanation from the moderators.

Hope this helps a lil

[winstondarmawan]

Is this in ideas for superconductors? If so this is very very far from what you need to know. From what I understand of it- two electrons can't spin in the same state inside a quantum system - cooper pairs don't follow this and spin in the same state. This along with the lattice structure vibrating so little at the critical temperatures means these pairs can form. - I think. Quantum numbers I do not know and I look forward to a better explanation from the moderators.

Hope this helps a lil

No, this is for Quanta to Quarks (option topic). However, the help is appreciated.

[kiwiberry]

Hello!
1. Can someone please explain Pauli's exclusion principle and electron's quantum numbers clearly? We went over it but I don't really understand it properly.
2. What are the things to look out for and include in a Prac Exam discussion? I lost many marks there and I'd like to avoid it in the future.
TIA

Not 100% confident with this, but I'll give it a shot
The four quantum numbers are:
- Principal quantum number (n) - describes the energy shells and the electron's distance from the nucleus
- Angular momentum quantum number (L) - describes the shape of orbit
- Magnetic quantum number (m_l) - describes the orientation of the electrons
- 'Spin' quantum number (m_s) - describes the spin axis of the electrons
Pauli's exclusion principle states that no two electrons can have the same 4 quantum numbers. This provided the reason for the maximum number of electrons in each shell, thus explaining the position of elements on the periodic table.

For prac discussions, the main things to talk about are reliability, accuracy, validity, and any improvements you could make. Hope that helped

[johnk21]

Can someone please help me with this HSC question for med physics.
Explain the difference in the relaxation times of hydrogen in water and the relaxation time of hydrogen in other molecules. (3 marks)

[winstondarmawan]

Hello! Can someone please help me understand this question, I have the answer but I do not understand it.
Question:
https://scontent-syd2-1.xx.fbcdn.net/v/t34.0-12/19433791_1250773725048148_1099258653_n.jpg?oh=d51a25252a0cfc50107a2c6784586cd9&oe=59508E20
https://scontent-syd2-1.xx.fbcdn.net/v/t34.0-12/19441301_1250773908381463_404155012_n.jpg?oh=95f7190931fa49c04e37e18e47b22826&oe=5950836F
Answer:
https://scontent-syd2-1.xx.fbcdn.net/v/t34.0-12/19244049_1250774138381440_1719650737_n.jpg?oh=5abcee2c34e5f38fd9843fa7176ddb7b&oe=5950D4BD

[Jyrgal]

Hello!

I just need to get my head around length contraction & time dilation haha, unfortunately alot of past papers/questions get this wrong and im extremely confused on whether my thinking is right

So let's say from a stationary frame of reference, someone views a planet of length L. When this someone climbs into a spaceship and flies at 0.8C, he sees the L get contracted, while time also decreases (not legit but an example: 1 second on spaceship=2seconds on the stationary reference). They should both decrease in proportion as C(speed of light)=Distance/Time is constant

Is this correct?

Thanks

[jakesilove]

Can someone please help me with this HSC question for med physics.
Explain the difference in the relaxation times of hydrogen in water and the relaxation time of hydrogen in other molecules. (3 marks)

Hey! Hydrogen ions in water have a very long relaxation time (T1 is about 4000 ms, T2 is about 2000 ms). However, Hydrogen ions in other substances have a much shorter relaxation time. This makes testing for water concentration very easy, as the 'signature' of water is very distinct!

[jakesilove]

Hello! Can someone please help me understand this question, I have the answer but I do not understand it.
Question:
https://scontent-syd2-1.xx.fbcdn.net/v/t34.0-12/19433791_1250773725048148_1099258653_n.jpg?oh=d51a25252a0cfc50107a2c6784586cd9&oe=59508E20
https://scontent-syd2-1.xx.fbcdn.net/v/t34.0-12/19441301_1250773908381463_404155012_n.jpg?oh=95f7190931fa49c04e37e18e47b22826&oe=5950836F
Answer:
https://scontent-syd2-1.xx.fbcdn.net/v/t34.0-12/19244049_1250774138381440_1719650737_n.jpg?oh=5abcee2c34e5f38fd9843fa7176ddb7b&oe=5950D4BD

Hey! I can't really read the question or the answer based on that link, but I THINK you're talking about how we tell how much to shift a graph by, when a stopping voltage has initially been applied, and then taken away?

So, the stopping voltage was originally 4.1V. When it is removed, we can calculate exactly how many 'extra' energy the electrons will have (remember, stopping voltage is energy used to 'restrain' electrons to the nucleus. Thus, if you remove the stopping voltage, the electrons will be able to fire off more easily!). Convert 4.1V to energy (I think the method is on the formula sheet). Then, set that equal to hf, and find the new 'threshold frequency'. Finally, make sure the graph has a gradient of 'h', and you're done!

Sorry that this isn't more comprehensive, I've got an exam tomorrow

[jakesilove]

Hello!

I just need to get my head around length contraction & time dilation haha, unfortunately alot of past papers/questions get this wrong and im extremely confused on whether my thinking is right

So let's say from a stationary frame of reference, someone views a planet of length L. When this someone climbs into a spaceship and flies at 0.8C, he sees the L get contracted, while time also decreases (not legit but an example: 1 second on spaceship=2seconds on the stationary reference). They should both decrease in proportion as C(speed of light)=Distance/Time is constant

Is this correct?

Thanks

Hey! Pretty much everything you've said above is correct! Sounds like you have a good understanding of the Space topic area However, I don't think that the ratio of length to time is always constant. The formulas just don't indicate as much. You've set the speed of light as velocity; in the frame of the light particle, then yes length over time is always constant. However, I'm not certain that this is the case for an observer travelling at less than the speed of light.

Basically, it doesn't matter, there's no point knowing/talking about this because it is outside the curriculum. Just focus on being able to use the formulas, and explain the principle.