HSC Physics Question Thread

[Zainbow]

For extended responses, if you opt to answer in dot points how exactly would you do that? How can I make sure it's clear enough and that there is flow to my answer? I've always answered in full sentences, and although I still prefer to do that in a few cases, there are some questions where dot points would be easier and favourable but I don't know the best method to approach that kind of response.

[Savas_P]

Hey! Great catch, that looks like an error! That working should be:



So your final answer should in fact be the answer given, divided by 5 -> 24.5 metres per second sorry for the error! First one I know of in those tests, I'll make sure it is fixed in the future

as pointed out on another forum, i am not sure if this is the final answer

delta x = Ux * t
1240 = Ux *(5)
Ux = 248 m/s

delta y = Uy*t - 1/2 *gt^2
0 = 5Uy - 1/2 * 9.8*25
Uy=24.5 m/s as jamon has said

but U = sqrt (Uy^2 + Ux^2)
which means the FINAL answer is U = 249.2072.. m/s @ 5°37'

hope this is right

[johnk21]

For extended responses, if you opt to answer in dot points how exactly would you do that? How can I make sure it's clear enough and that there is flow to my answer? I've always answered in full sentences, and although I still prefer to do that in a few cases, there are some questions where dot points would be easier and favourable but I don't know the best method to approach that kind of response.

To be honest, its completely fine to always write in dotpoint form; however its NOT okay to do what they call an 'info dump'.
Here is an example how dotpoints could be used in say the BCS theory:
Conditions for BCS Theory to work:
- Must be a Type I superconductor
- Temperature must be below critical temperature where lattice vibrations are at a minimum
Once these set conditions are achieved, the BCS Theory is accountable for superconductivity.
- Firstly an electron causes the positive lattice to be distorted -> creates a net positive region
- Another electron is attracted to this region
- A phonon is released due to the lattice distortion, and is absorbed by the electron to overcome electrostatic force of other electron
- Both electrons form a cooper pair, allowing for zero resistance as it is unimpeded

Note: Not saying dotpoints are desirable in this specific question (i personally wouldnt), but dotpoints are good for even 6 and 7 markers such as quantum theory ones were you want to briefly talk about planck and einstein, and show their relation as well as providing a judgement.
Hope i helped

[winstondarmawan]

Would appreciate help with the following MCs:
13. https://scontent-syd2-1.xx.fbcdn.net/v/t34.0-12/22414729_1347448845380635_323509929_n.jpg?oh=134c4ab9f911a5324356ef6198cfc21c&oe=59DFE736
https://scontent-syd2-1.xx.fbcdn.net/v/t34.0-12/22386637_1347448898713963_942589714_n.jpg?oh=2ea0b0e92ae1cdc8e1af5165ca2a0c3c&oe=59DFB08E
14. https://scontent-syd2-1.xx.fbcdn.net/v/t34.0-12/22447103_1347448998713953_512491506_n.jpg?oh=356849cd6400b6bee39669ea6fc0fb11&oe=59E0A675
And also, can someone please tell me that this question is impossible (if not how do I do it):
https://scontent-syd2-1.xx.fbcdn.net/v/t34.0-12/22471704_1347448518714001_1038035986_n.jpg?oh=18c9c49a3b603443015d3a57eddae686&oe=59DFA088
Thanks in advance!

Bump

[jamonwindeyer]

as pointed out on another forum, i am not sure if this is the final answer

delta x = Ux * t
1240 = Ux *(5)
Ux = 248 m/s

delta y = Uy*t - 1/2 *gt^2
0 = 5Uy - 1/2 * 9.8*25
Uy=24.5 m/s as jamon has said

but U = sqrt (Uy^2 + Ux^2)
which means the FINAL answer is U = 249.2072.. m/s @ 5°37'

hope this is right

Yeah you've got it - The working he spotted the error in was an extract from the full solution in the Notes he referenced, but thanks for popping the full thing up!

[Iminschool]

Q13 Winston

[jamonwindeyer]

Bump

Q14: Consider the direction of holes first! They are moving into the page, the magnetic field is to the right, the resultant force is downwards.

Next, electrons. They are moving out of the page (opposite direction to current flow), magnetic field is to the right, the resultant force (negative charged particle) is also downwards by the right hand slap rule. So, they move in the same direction!

You might need to fiddle with the right hand slap rule (or similar) to make sense of this - Let me know if I can clarify!
For that other question, 33 right? Definitely possible, it looks like the method shown in your photo is correct! Energy of emitted photoelectron will be the energy per photon minus the work function, in other words:



Is this the question you meant? Any part of the solution in the image particularly giving you trouble?

[winstondarmawan]

Q13 Winston

Q14: Consider the direction of holes first! They are moving into the page, the magnetic field is to the right, the resultant force is downwards.

Next, electrons. They are moving out of the page (opposite direction to current flow), magnetic field is to the right, the resultant force (negative charged particle) is also downwards by the right hand slap rule. So, they move in the same direction!

You might need to fiddle with the right hand slap rule (or similar) to make sense of this - Let me know if I can clarify!
For that other question, 33 right? Definitely possible, it looks like the method shown in your photo is correct! Energy of emitted photoelectron will be the energy per photon minus the work function, in other words:



Is this the question you meant? Any part of the solution in the image particularly giving you trouble?

Thank you guys!
For 33, the resulting KE is negative, so I thought it was an error. Is it possible for KE to be negative?

[pikachu975]

Thank you guys!
For 33, the resulting KE is negative, so I thought it was an error. Is it possible for KE to be negative?

No since KE = 1/2 mv^2 and m is positive and v^2 is positive

[jamonwindeyer]

Thank you guys!
For 33, the resulting KE is negative, so I thought it was an error. Is it possible for KE to be negative?

No since KE = 1/2 mv^2 and m is positive and v^2 is positive

Ahhh didn't catch that, well if the answer ends up negative what that means is that you in fact don't have enough energy to free any electrons (indeed, can't have negative energy, it just means that nothing happens). So, the maximum kinetic energy is 0J - Trick question!

[bsdfjnlkasn]

Q14: Consider the direction of holes first! They are moving into the page, the magnetic field is to the right, the resultant force is downwards.

Next, electrons. They are moving out of the page (opposite direction to current flow), magnetic field is to the right, the resultant force (negative charged particle) is also downwards by the right hand slap rule. So, they move in the same direction!

You might need to fiddle with the right hand slap rule (or similar) to make sense of this - Let me know if I can clarify!
For that other question, 33 right? Definitely possible, it looks like the method shown in your photo is correct! Energy of emitted photoelectron will be the energy per photon minus the work function, in other words:



Is this the question you meant? Any part of the solution in the image particularly giving you trouble?

Hey there!

I was just wondering if for that 2 marker, you could find the energy of the photoelectrons emitted because you're given the wavelength? Then you can just plug it into E = hf? Then by comparing what the value of the emitted electrons are and what the minimum required is (Ek min), then you can deduce that because the calculated value is less than the minimum, that no photoelectrons will be emitted?

[jamonwindeyer]

Hey there!

I was just wondering if for that 2 marker, you could find the energy of the photoelectrons emitted because you're given the wavelength? Then you can just plug it into E = hf? Then by comparing what the value of the emitted electrons are and what the minimum required is (Ek min), then you can deduce that because the calculated value is less than the minimum, that no photoelectrons will be emitted?

Yeah absolutely, that would be the approach! I suppose it is just that a HSC exam would never throw you a trick question like that, but still very easy to deduce that you won't get any photoelectrons

[itssona]

hiii question about the pendulum prac (and all prac tho);
in the conclusion of the prac report, should we include how we can minimise errors and improve our method?

also im confused,
we always learnt that reliability is associated with repetition, so how come all answers to questions about reliability, associate with accuracy?  why do they all overlap :/

thank you

[arunasva]

hiii question about the pendulum prac (and all prac tho);
in the conclusion of the prac report, should we include how we can minimise errors and improve our method?

also im confused,
we always learnt that reliability is associated with repetition, so how come all answers to questions about reliability, associate with accuracy?  why do they all overlap :/

thank you

Yes, you should mention how you avoided error which includes taking precise mearuerments and from the centre each time (accuracy). Ensure only the variable you are testing gets changed WHICH IS LENGTH OF THE STRING and angle of displacement on each side is constant. (validity) and doing more repetitions to see if the result is reproducible (reliability). Reliability and accuracy both are two separate things that need to be maintained in a dataset hence they are asked together but separately. Its like find the area of a triangle  and find the length of all its sides. two separate things.

[itssona]

Yes, you should mention how you avoided error which includes taking precise mearuerments and from the centre each time (accuracy). Ensure only the variable you are testing gets changed WHICH IS LENGTH OF THE STRING and angle of displacement on each side is constant. (validity) and doing more repetitions to see if the result is reproducible (reliability). Reliability and accuracy both are two separate things that need to be maintained in a dataset hence they are asked together but separately. Its like find the area of a triangle  and find the length of all its sides. two separate things.

Omg thank you!!!