Login | Register
FREE Head Start Lectures this January - book now! HSC: register here | QCE: register here | VCE: register here

Welcome, Guest. Please login or register.

January 25, 2020, 08:28:51 pm

### AuthorTopic: QCE Physics Questions Thread  (Read 683 times)

0 Members and 1 Guest are viewing this topic.

#### Joseph41

• Administrator
• Great Wonder of ATAR Notes
• Posts: 10031
• Oxford comma and Avett Brothers enthusiast.
• Respect: +6663
##### QCE Physics Questions Thread
« on: January 30, 2019, 03:38:39 pm »
+6
QCE PHYSICS Q&A THREAD

What is this thread for?
If you have general questions about the QCE Physics course (both Units 1&2 and 3&4) or how to improve in certain areas, this is the place to ask! 👌

Who can/will answer questions?
Everyone is welcome to contribute; even if you're unsure of yourself, providing different perspectives is incredibly valuable.

Please don't be dissuaded by the fact that you haven't finished Year 12, or didn't score as highly as others, or your advice contradicts something else you've seen on this thread, or whatever; none of this disqualifies you from helping others. And if you're worried you do have some sort of misconception, put it out there and someone else can clarify and modify your understanding!

There'll be a whole bunch of other high-scoring students with their own wealths of wisdom to share with you, so you may even get multiple answers from different people offering their insights - very cool.

To ask a question or make a post, you will first need an ATAR Notes account. You probably already have one, but if you don't, it takes about four seconds to sign up - and completely free!

#### K.Smithy

• QLD MVP - 2019
• Trendsetter
• Posts: 155
• Yes, that is a lizard on my head.
• Respect: +150
##### Re: QCE Physics Questions Thread
« Reply #1 on: October 06, 2019, 12:03:23 am »
0
Hi!

I'm currently doing some work on calculating forces in 2-dimensions (when given the distance between charged particles and the charge of the particles), and there is this one worked example that I just don't understand.

I've attached photos of the question, the first photo should be the one that contains "worked example 6.1C" - I understand all of this, it is just attached for context for "worked example 6.1D". I don't understand W.E. 6.1D - what is X? Why do we need X? Why are we multiplying 90 by 1/2? How does using the first method get the same answer as using cosine rule?... I just don't get this question.

Cheers
QCE 2020: Physics || Psychology || Biology || Mathematical Methods || General English || Study of Religion

#### K.Smithy

• QLD MVP - 2019
• Trendsetter
• Posts: 155
• Yes, that is a lizard on my head.
• Respect: +150
##### Re: QCE Physics Questions Thread
« Reply #2 on: October 06, 2019, 12:04:26 am »
0
Here is the second image (the one with the question I am struggling with). I couldn't attach both to one post, sorry.
QCE 2020: Physics || Psychology || Biology || Mathematical Methods || General English || Study of Religion

#### DrDusk

• NSW MVP - 2019
• Forum Obsessive
• Posts: 492
• I exist in the fourth dimension
• Respect: +121
##### Re: QCE Physics Questions Thread
« Reply #3 on: October 06, 2019, 12:20:16 am »
+2
Here is the second image (the one with the question I am struggling with). I couldn't attach both to one post, sorry.
I already don't like this textbook.. lol

Okay so basically what they've done with the whole X thing is create a right angled triangle with the angle theta in the little diagram being 90 degrees, because this would mean

$\cos\bigg(\dfrac{\pi}{4}\bigg) = \dfrac{XB}{90} \Rightarrow XB^2 = \dfrac{1}{2}\times 90^2$

This is just so that with a right angled triangle you can use your standard sin and cos stuff.

If I were you, just use the cosine rule. It's much less tedious
« Last Edit: October 06, 2019, 12:56:06 am by DrDusk »
HSC/Prelim Physics tutor
BSc(Advanced)(Hons Adv Physics)/BSc(Computer Science) in Cyber-Security @ UNSW 2019

#### K.Smithy

• QLD MVP - 2019
• Trendsetter
• Posts: 155
• Yes, that is a lizard on my head.
• Respect: +150
##### Re: QCE Physics Questions Thread
« Reply #4 on: October 06, 2019, 02:39:19 pm »
+2
I already don't like this textbook.. lol

Oml this textbook is a godsend compared to my Unit 1 & 2 textbook.

Okay so basically what they've done with the whole X thing is create a right angled triangle with the angle theta in the little diagram being 90 degrees, because this would mean

$\cos\bigg(\dfrac{\pi}{4}\bigg) = \dfrac{XB}{90} \Rightarrow XB^2 = \dfrac{1}{2}\times 90^2$

This is just so that with a right angled triangle you can use your standard sin and cos stuff.

Oh... duh... wow, I should have got that.... welp

If I were you, just use the cosine rule. It's much less tedious

Aha yeah, I much prefer cosine rule.

Thank you so much!!!
QCE 2020: Physics || Psychology || Biology || Mathematical Methods || General English || Study of Religion

#### alphabeta

• Adventurer
• Posts: 17
• Class of 2020
• Respect: 0
##### Re: QCE Physics Questions Thread
« Reply #5 on: December 29, 2019, 10:11:09 pm »
0
Hi everyone!

I am trying to figure out the inclined planes part of the QLD syllabus. I decided to try a QCAA question and couldn't solve it. Can someone explain how to do Q28 on paper 1 of the sample external exam for physics. I also need some great advice in general with this section, especially solving problems. Thanks!!
QCE 2020:

Literature [], Chemistry [], Physics [], Methods [], Specialist []

#### RuiAce

• ATAR Notes Lecturer
• Honorary Moderator
• Great Wonder of ATAR Notes
• Posts: 8706
• "All models are wrong, but some are useful."
• Respect: +2490
##### Re: QCE Physics Questions Thread
« Reply #6 on: December 29, 2019, 10:40:03 pm »
+7
Hi everyone!

I am trying to figure out the inclined planes part of the QLD syllabus. I decided to try a QCAA question and couldn't solve it. Can someone explain how to do Q28 on paper 1 of the sample external exam for physics. I also need some great advice in general with this section, especially solving problems. Thanks!!

There were a few steps required in this question. Let me know if there's anything you wish for me to elaborate more on.
« Last Edit: December 29, 2019, 10:49:13 pm by RuiAce »

#### alphabeta

• Adventurer
• Posts: 17
• Class of 2020
• Respect: 0
##### Re: QCE Physics Questions Thread
« Reply #7 on: December 30, 2019, 11:16:31 am »
+1
Thanks Rui!

That makes sense now!. I was aware of all the steps, except didn't realise to treat the upwards applied force as friction. Thanks so much!
QCE 2020:

Literature [], Chemistry [], Physics [], Methods [], Specialist []

#### alphabeta

• Adventurer
• Posts: 17
• Class of 2020
• Respect: 0
##### Re: QCE Physics Questions Thread
« Reply #8 on: January 02, 2020, 11:42:36 am »
0
Hi everyone! Me again.

I just wanted to check that I have done Q2 of the Physics practice external exam (paper 2) correctly.

So, what I have done is found the magnitude, which I got:

$4*10^-5$

And for direction, I said into the page. This is the part I'm a little unsure about, as I don't quite know how much my fingers should bend. Could someone please check if what I have done is right lol?

Thanks, everyone!
QCE 2020:

Literature [], Chemistry [], Physics [], Methods [], Specialist []

#### RuiAce

• ATAR Notes Lecturer
• Honorary Moderator
• Great Wonder of ATAR Notes
• Posts: 8706
• "All models are wrong, but some are useful."
• Respect: +2490
##### Re: QCE Physics Questions Thread
« Reply #9 on: January 02, 2020, 12:08:55 pm »
+3
Hi everyone! Me again.

I just wanted to check that I have done Q2 of the Physics practice external exam (paper 2) correctly.

So, what I have done is found the magnitude, which I got:

$4*10^-5$

And for direction, I said into the page. This is the part I'm a little unsure about, as I don't quite know how much my fingers should bend. Could someone please check if what I have done is right lol?

Thanks, everyone!

It’s definitely into the page.

Your thumb points in the direction of the current (which presumably you go urged yourself). Then curl up your fingers all the way. On the right of the wire, the fingers curl into the page.

(I wouldn’t actually know how the magnitude works - was never taught it. Will let someone else check your value haha)

#### blasonduo

• MOTM: OCT 17
• HSC Moderator
• Forum Obsessive
• Posts: 386
• Schrodinger waved while Heisenberg didn't?
• Respect: +301
##### Re: QCE Physics Questions Thread
« Reply #10 on: January 02, 2020, 12:27:26 pm »
+3
Hi everyone! Me again.

I just wanted to check that I have done Q2 of the Physics practice external exam (paper 2) correctly.

So, what I have done is found the magnitude, which I got:

$4*10^-5$

And for direction, I said into the page. This is the part I'm a little unsure about, as I don't quite know how much my fingers should bend. Could someone please check if what I have done is right lol?

Thanks, everyone!

Hey! By doing the question, I do get the same answer as you Just remember to always give units.

As Rui said, you use the right-hand grip rule
HSC 2017 l Physics (medical) l Chemistry (forensic) l Biology (communication) l Maths 2u l Maths 3u l standard english

2018: UNSW B science (physics)/B education

Lol, no one cares about my uni courses.

Want to join the werewolf hunt? Click here!

HSC Physics Topics 1 & 2 Exam!

#### alphabeta

• Adventurer
• Posts: 17
• Class of 2020
• Respect: 0
##### Re: QCE Physics Questions Thread
« Reply #11 on: January 02, 2020, 01:57:15 pm »
+2
Quote
It’s definitely into the page.

Your thumb points in the direction of the current (which presumably you go urged yourself). Then curl up your fingers all the way. On the right of the wire, the fingers curl into the page.

(I wouldn’t actually know how the magnitude works - was never taught it. Will let someone else check your value haha)
Thanks for clearing that up Rui! I wasn't sure to curl my fingers up completely, but now I know. Thanks.

Quote
Hey! By doing the question, I do get the same answer as you Just remember to always give units.

As Rui said, you use the right-hand grip rule
Yay! Thanks blasonduo! And thanks for the reminder too, I'll remember the 'T' next time.
QCE 2020:

Literature [], Chemistry [], Physics [], Methods [], Specialist []