HSC Physics Question Thread

[jamonwindeyer]

Hi!
Can you please help with this question (from AC generators)?

Sketch graphs to show the relationship between:
(a) The flux through the coil and the induced
voltage.
(b) The torque acting on the coil and the induced voltage.

The answers show a sine relationship for (a), and a cosine relationship for (b) - but I can't seem to reason as to why. I thought that, for (a) - as flux increases to some maximum value, induced emf would decrease - and for (b) some sort of direct (not necessarily directly proportional) relationship would occur. Also, I'm a bit confused as to how both flux and torque can be on the x-axis (in the suggested answers) when, in a generator, they don't increase indefinitely?

Thank you in advance for your assistance!

Hello! I think there might be some issue with your question here, because you certainly shouldn't have a sinusoidal relationship between flux and voltage. Really, drawing a graph linking flux and induced emf is a faulty exercise, because induced emf depends on rate of change of flux. So you can't draw any sort of direct relationship between flux and emf.

Could you perhaps attach a picture of the graphs? Or a Dropbox link to an image or similar? Maybe I'm interpreting it incorrectly, but I'd tend to agree more with your points

[jamonwindeyer]

Hi I'm in Year 11,

I am having trouble understanding the topic area of distance and displacement on horizontal planes, in particular the maths side of questions and formulas. Any guidance/ links to resources will be greatly appreciated.

Kind Regards,

Coolmate 

Hey Coolmate!! Tough stuff for sure! the general approach to any of these questions is roughly the same:

- Break/resolve any given vector into two perpendicular pieces (ie - horizontal/vertical, north-south/east-west, etc)
- Perform your kinematics calculations on each direction separately, yielding one 'result' in each direction
- Recombine your two results into a single vector using trigonometry

If you attach an example of a question you are having trouble with, we'd be happy to step through it for you

[Jefferson]

Hi all,
Could someone show me how to solve this relative velocity problem using relative velocity vectors.

Angelica is inside train A moving at 80km/h South and sees Bob inside car B moving at 100 km/h at 300° T.
What is Bob's velocity relative to the ground?

Answers are 92km/h and 251° T.

Attachment below is what I did.

[louisaaa01]

Hello! I think there might be some issue with your question here, because you certainly shouldn't have a sinusoidal relationship between flux and voltage. Really, drawing a graph linking flux and induced emf is a faulty exercise, because induced emf depends on rate of change of flux. So you can't draw any sort of direct relationship between flux and emf.

Could you perhaps attach a picture of the graphs? Or a Dropbox link to an image or similar? Maybe I'm interpreting it incorrectly, but I'd tend to agree more with your points

I've attached the question and provided answer

[david.wang28]

Hi all,
Could someone show me how to solve this relative velocity problem using relative velocity vectors.

Angelica is inside train A moving at 80km/h South and sees Bob inside car B moving at 100 km/h at 300° T.
What is Bob's velocity relative to the ground?

Answers are 92km/h and 251° T.

Attachment below is what I did.

Your working out is fine. Don't need to worry about relative velocity vectors.

[david.wang28]

Hello,
I am stuck on all of the multiple choice questions and Q 2.1 b) in the link below. Can anyone please help me out? Thanks

[_Himani_]

Hey,
I was just wondering how I should prepare for a Processing and Data Analysis In-Class Assessment on modules 5 and 6. Where can I find questions to attempt? Would the general examples from the In Focus textbook be enough?
As always,
Thank You Very Much.

[jamonwindeyer]

Hello,
I am stuck on all of the multiple choice questions and Q 2.1 b) in the link below. Can anyone please help me out? Thanks

Sure thing David!

- 1.1 is (D), because all the others have nonsense words with nothing to do with anything
- 1.2 you are right with (D)
- 1.3 is (B), the energy of an emitted photoelectron is \(E=hf-\phi\). It has nothing to do with intensity, only the frequency of light and the work function of the metal.
- 1.3 is C), because that's just how it was

As for the last one, remember that the energy of emitted photoelectrons is always \(E=hf-\phi\). Again, intensity has nothing to do with that - Intensity only releases MORE photoelectrons, it doesn't change their individual energies. Therefore, if the light doesn't have a high enough frequency, you won't get a photocurrent no matter how intense your light is

[david.wang28]

Hey,
I was just wondering how I should prepare for a Processing and Data Analysis In-Class Assessment on modules 5 and 6. Where can I find questions to attempt? Would the general examples from the In Focus textbook be enough?
As always,
Thank You Very Much.

You can buy the topic tests from atarnotes of course

[david.wang28]

Sure thing David!

- 1.1 is (D), because all the others have nonsense words with nothing to do with anything
- 1.2 you are right with (D)
- 1.3 is (B), the energy of an emitted photoelectron is \(E=hf-\phi\). It has nothing to do with intensity, only the frequency of light and the work function of the metal.
- 1.3 is C), because that's just how it was

As for the last one, remember that the energy of emitted photoelectrons is always \(E=hf-\phi\). Again, intensity has nothing to do with that - Intensity only releases MORE photoelectrons, it doesn't change their individual energies. Therefore, if the light doesn't have a high enough frequency, you won't get a photocurrent no matter how intense your light is

Thanks Jamon!

[jamonwindeyer]

Hey,
I was just wondering how I should prepare for a Processing and Data Analysis In-Class Assessment on modules 5 and 6. Where can I find questions to attempt? Would the general examples from the In Focus textbook be enough?
As always,
Thank You Very Much.

These are hard to prepare for!! It's really just about building your general understanding of the topics. As David so kindly mentions above, you can buy the AN Topic Tests for that purpose but of course, Physics In Focus or anything you already have will do just fine as well!!

On top of that, make sure you practice experiment skills. Validity/accuracy/reliability, graphing skills, variables, sources of error, that sort of stuff if you needed any of that clarified let us know!

[jamonwindeyer]

Thanks Jamon!

You're welcome! Happy to help

[david.wang28]

Hello,
I have trouble with all of Q 2.3 in the attachment below. Can anyone please help me out? Thanks

[Dillan]

Hey everyone,

Got a physics depth study due soon on motors in particular DC ones.

Was just after a few ideas of an inquiry question to base my depth study on.

Also if anyone has any tips and tricks on writing writing a band 6 depth study, would be greatly appreciated if you can send it my way

Cheers

[jamonwindeyer]

Hello,
I have trouble with all of Q 2.3 in the attachment below. Can anyone please help me out? Thanks

Hey David! How did you end up going with this? If you are struggling with an entire worksheet of questions on a topic it is probably worth going back to the notes/textbook on the topic, watching some YouTube videos, etc. It will be better for you than just having the answers served to you by someone else!! I'd also wager that wanting 10 questions worth of answers is probably why you didn't get much of a response to this post - You'll get help much faster if you work with us a bit and show us what understanding you do have and where your confusions lie