HSC Physics Question Thread

[jamonwindeyer]

2. Can you explain the changing acceleration of a rocket during launch in terms of the Law of Conservation of Momentum? (straight from the dot point haha) What are we expected to know for this?

Thanks

In addition to the above great answer, let me link you to this guide on rocket launches! It goes into a few bits of info that will help with that dot point

[limtou]

In addition to the above great answer, let me link you to this guide on rocket launches! It goes into a few bits of info that will help with that dot point

Thanks Jamon!
Just another query, I have attached below the sample answer for a past school question on rocket launch and the momentum involved... and it states that the rocket is continually gaining momentum? Is this correct? I thought the rocket has a constant momentum so that with decreasing mass, there is increasing velocity.
Please explain, thanks!

[limtou]

Have a few more questions,
Could you explain how to draw the loops of flux for a)? I don't particularly understand the marking criteria.
And please explain the answer for q5 multiple choice

Thank you~

[Aaron12038488]

im so nervous that in 1 more term im in year 12!. My weakest subject by far is Physics. Looking at the schedule of assessments (2016) it says I have a practical which is worth 15%. My teacher said it was on MOtors and Generators. Its held on Term 1 week 4 and it states 5% is based on knowledge and understanding, and 10% on skills in planning and conducting investigations, however 0 in Skills in communicating information, scientific thinking, problem solving and working as an individual/teamwork.
What will the prac likely be on, ahha sorry if this post is queer. thx.

[jakesilove]

Thanks Jamon!
Just another query, I have attached below the sample answer for a past school question on rocket launch and the momentum involved... and it states that the rocket is continually gaining momentum? Is this correct? I thought the rocket has a constant momentum so that with decreasing mass, there is increasing velocity.
Please explain, thanks!

Hey! 'Gaining' momentum is definitely a silly way to put it; however, it does get the point across, and is correct. Basically, there are two separate things going on here.

Firstly, remember that momentum must always be conserved. The gas has mass, and is moving at some velocity downwards. Therefore, the fuel has a momentum in the downwards direction (let's call this negative). By conservation of momentum, there must also be some sort of momentum UPWARDS to cancel out this downwards push. Therefore, the rocket accelerates upwards, and 'gains' momentum. Net change in momentum is zero; gas goes down, rocket goes up.

The second principle is the one you've described. As the rocket goes upwards, it loses mass, and thus increases its velocity.

But yeah, Rocket definitely increases its total momentum as fuel gets pushed out the bottom

[jamonwindeyer]

Have a few more questions,
Could you explain how to draw the loops of flux for a)? I don't particularly understand the marking criteria.
And please explain the answer for q5 multiple choice

Thank you~

Hey! You need to draw two loops, both circles going through the core and the bar. They cannot cross (magnetic field lines produced by a field in this fashion never do). They should also stay roughly the same distance apart as they travel around the coil, through the bar, back into the coil and to the end of the loop

For the multiple choice - When we do work putting something into orbit, that work is converted to two types of energy (neglecting losses). Kinetic energy (getting the object moving), and potential energy (raising the object in the field). In other words:

[jamonwindeyer]

im so nervous that in 1 more term im in year 12!. My weakest subject by far is Physics. Looking at the schedule of assessments (2016) it says I have a practical which is worth 15%. My teacher said it was on MOtors and Generators. Its held on Term 1 week 4 and it states 5% is based on knowledge and understanding, and 10% on skills in planning and conducting investigations, however 0 in Skills in communicating information, scientific thinking, problem solving and working as an individual/teamwork.
What will the prac likely be on, ahha sorry if this post is queer. thx.

Chances are it will be based on electromagnetic induction - At least, that is what makes the most sense in my head don't stress about it yet though! You don't know the content yet, and you've got Prelim exams before that - You seriously shouldn't be preparing for any Year 12 assessments just yet

[left right gn]

I have an upcoming assignment requires me to perform an investigation to model the behaviour of semiconductors, including the creation of a hole or positive charge on the atom that has lost the electron and the movement of electrons and holes in opposite directions when an electric field is applied across the semiconductor.

Any suggestions on the model?

[winstondarmawan]

I have an upcoming assignment requires me to perform an investigation to model the behaviour of semiconductors, including the creation of a hole or positive charge on the atom that has lost the electron and the movement of electrons and holes in opposite directions when an electric field is applied across the semiconductor.

Any suggestions on the model?

Try students in a classroom. N-type you can have an extra student who does not require seats to move around, and p-type you can have an extra vacant seat.

[left right gn]

Try students in a classroom. N-type you can have an extra student who does not require seats to move around, and p-type you can have an extra vacant seat.

Any other ideas that do not require students as a part of my model?

[seventeenboi]

HIHI
dumbass me is still struggling to understand the inconsistencies of the classical theory's interpretation of blackbody radiation and the UV catastrophe so far i know that they thought that emission was dependent on frequency, and that energy is absorbed is continuous ( that is, can occur at any amount and increases as wavelength becomes shorter except this true, but only applies to longer wavelengths)

could someone directly pinpoint and outline specifically ALL the things that were wrong with it?

cheers

[winstondarmawan]

Hello! Need help with the following Q, TIA.
https://scontent-syd2-1.xx.fbcdn.net/v/t34.0-12/19668099_1262289940563193_1371043497_n.png?oh=465b02f227d5f6f6ed9bc5344f18bb25&oe=595E44A2

[pikachu975]

Hello! Need help with the following Q, TIA.
https://scontent-syd2-1.xx.fbcdn.net/v/t34.0-12/19668099_1262289940563193_1371043497_n.png?oh=465b02f227d5f6f6ed9bc5344f18bb25&oe=595E44A2

The particle model of light states that light is carried in photons which are quantised packets of energy with E = hf. You'd contrast them by saying they have different frequencies which means different energies by E = hf. You have to use the stimulus given so probably reference that they would have the same brightness because brightness of a light can be measured by Watts. This is because they give that they have the same intensity so Intensity = Wm^-2 and m^-2 and Intensity would be equal, so Watts are equal. That should be enough for 2 marks!

[JeffChiang]

What exactly is magnetic flux and magnetic flux density?
Still remain somewhat confused from this dot point.
From my understanding, magnetic flux= number of magnetic field lines
                                       magnetic flux density= number of magnetic field lines per unit area
So, if you were given a question to compare two coils in a magnetic field, would you literally count the amount of lines that run through the coil?
Is magnetic flux density the same as the strength of a magnetic field?
Thanks

[jamonwindeyer]

Any other ideas that do not require students as a part of my model?

You could perhaps do the same thing with a drawn grid and counters? The basic principle could probably be modelled in many ways (students, cars and parking spaces, counters/markers, etc)