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November 29, 2021, 01:19:55 am

Author Topic: 2 questions about the physics exam  (Read 1046 times)  Share 

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Samueliscool223

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2 questions about the physics exam
« on: October 16, 2021, 08:43:58 pm »
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1) Why do they not allow you to use calculus in the exam when they expect you to know stuff like how the EMF-time function doubles in amplitude and halves in period when you double the rotation speed? stuff like that requires knowledge of the chain rule which is not mentioned in the book whatsoever. Additionally, I remember seeing a question that requires you to know the area under the graph of a velocity-time function gives the distance travelled. that requires knowledge of integrational calculus, and is not mentioned in the study design.

Also, how do you know how many significant figures/decimal places youre supposed to round to when they dont specify?

ashmi

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Re: 2 questions about the physics exam
« Reply #1 on: October 16, 2021, 09:33:57 pm »
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1) Why do they not allow you to use calculus in the exam when they expect you to know stuff like how the EMF-time function doubles in amplitude and halves in period when you double the rotation speed? stuff like that requires knowledge of the chain rule which is not mentioned in the book whatsoever. Additionally, I remember seeing a question that requires you to know the area under the graph of a velocity-time function gives the distance travelled. that requires knowledge of integrational calculus, and is not mentioned in the study design.

Also, how do you know how many significant figures/decimal places youre supposed to round to when they dont specify?

1. VCE Physics is made to be accessible for any student regardless if they are doing a VCE Maths or not. The exam questions are made such that people who do not take a maths subject beyond year 10 can still do the exam. There are no prerequisites to doing VCE Physics maths wise so it is expected that you have at least a strong Year 10 Mathematics background, hence calculus is generally not used. This, however, does not stop you from using your knowledge of calculus to help you with some questions! Really, so long as you know what a gradient and area is, you are pretty much all set to go.

1a. For EMF-Time, being able to think qualitatively about what happens is far more important as this will eventually show you how to graphically represent it. So when you double the rotation speed what happens? Does the change in flux increase or decrease? Does this then change the EMF? If I double the rotation speed what will happen to my period?

1b. Alright so velocity-time graph. If I do velocity * time, you will notice that a unit of meters pops out. What do we associate meters to be? Usually some sort of displacement measurement.

Finding an area of a graph provided that is has a grid behind the 'line' definitely does not need integration calculus (in reference for a VCE Physics exam). At best you would be asked to approximately find the area of each 'box' then multiply by roughly how many boxes fill the area of the graph to get your desired measurement.

2. When not stated, use the sig figures in the question. They are not as picky as other subjects (E.g. Chemistry) provided that it is reasonable, however, when stated they mark extremely harshly in this area.

TLDR: They cannot assume everyone does a VCE Maths subject hence everything is based on a year 10 mathematics background. There are many ways to answer a physics question, however, some ways are far easier than others. Go with sig figs and be reasonable.

Samueliscool223

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Re: 2 questions about the physics exam
« Reply #2 on: October 16, 2021, 11:21:09 pm »
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yea nvm maybe that period one was a bad example, i guess u can think about it without needing calculus knowledge. but an example where you might need knowledge of calculus would be when they ask you to graph induced voltage-time graphs, when given flux-time graphs or information. because that requires knowledge of the instantaneous gradient at any given x point, aka the derivative. kids who dont know calculus are basically screwed, like if i only did further maths and i got asked that question i would be shitting myself. so it really disadvantages those who dont do methods/spesh, hence why i think its pretty stupid how they dont make any mention of differential calculus in the course or straight up allow you to use differentiation or integration in the exam.

also, your method of "deducing" displacement has something to do with the area is clearly arbitrary, and does not work when applying it to the area under a force-displacement graph, which is the work done; there is no obvious link between Newtons (the unit of force) and the work done. Thus, you simply cannot know the area under a velocity-time function is equal to the displacement, without it being explicitly told to you (which it is not in the study design nor in the textbooks), or without having some basic background calculus knowledge, and thus that question has a major flaw, in that it disadvantages those vcaa is trying NOT to disadvantage.
and i never said you need to use calculus for finding the actual area, just that you need calculus knowledge to understand what to do for that specific question.

do you now see why im confused about why they dont let you use calculus?

ashmi

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Re: 2 questions about the physics exam
« Reply #3 on: October 17, 2021, 09:38:42 am »
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yea nvm maybe that period one was a bad example, i guess u can think about it without needing calculus knowledge. but an example where you might need knowledge of calculus would be when they ask you to graph induced voltage-time graphs, when given flux-time graphs or information. because that requires knowledge of the instantaneous gradient at any given x point, aka the derivative. kids who dont know calculus are basically screwed, like if i only did further maths and i got asked that question i would be shitting myself. so it really disadvantages those who dont do methods/spesh, hence why i think its pretty stupid how they dont make any mention of differential calculus in the course or straight up allow you to use differentiation or integration in the exam.

also, your method of "deducing" displacement has something to do with the area is clearly arbitrary, and does not work when applying it to the area under a force-displacement graph, which is the work done; there is no obvious link between Newtons (the unit of force) and the work done. Thus, you simply cannot know the area under a velocity-time function is equal to the displacement, without it being explicitly told to you (which it is not in the study design nor in the textbooks), or without having some basic background calculus knowledge, and thus that question has a major flaw, in that it disadvantages those vcaa is trying NOT to disadvantage.
and i never said you need to use calculus for finding the actual area, just that you need calculus knowledge to understand what to do for that specific question.

do you now see why im confused about why they dont let you use calculus?

1. If you are given a flux-time graph and want to turn it into an emf-time graph, there is absolutely nothing stopping you from taking the negative derivative! Not too sure if it helps, but I had plenty of friends while doing 3/4 Physics that did no VCE Maths at all. What they have said regarding this particular question is just knowing what does it mean when the gradient is 0 and what it means when the gradient is steep then connect the dots. This type of stuff is taught in class (well my teacher did because he knew a lot of us didn't do a VCE Maths) and hopefully it is taught somewhat similar like that around at other schools. The reason why it isn't mentioned in the study design is simple, you don't need it. As in my last post, if you know what an area or a gradient is, you are good to go.

2. Alright so now we are moving onto a force-displacement graph. So for this one, in fact, the technique above does work, it is just you need to understand what the units it pops out to be is. It is like when you have impulse, there are two types of units you can use. Maybe have a go at trying to see what the unit you come out with is and seeing if there is an equivalent unit (you will need to understand the unit that pops out for you to be able to figure out what measurement it is referring to). Once again, a lot of my friends didn't do VCE Maths at all and they also have said that finding an area has been no problem. VCAA will always accept a range of answers for the area under a graph scenario, so don't stress! Also, I'm not too sure what textbook you are using, but I am pretty sure the one I used in year 12 stated it very clearly what the areas and gradients mean (I mean also doing a unit check is encouraged, especially if you do physics in university).

Hope that helps!

Samueliscool223

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Re: 2 questions about the physics exam
« Reply #4 on: October 23, 2021, 03:02:38 pm »
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yea nvm maybe that period one was a bad example, i guess u can think about it without needing calculus knowledge. but an example where you might need knowledge of calculus would be when they ask you to graph induced voltage-time graphs, when given flux-time graphs or information. because that requires knowledge of the instantaneous gradient at any given x point, aka the derivative. kids who dont know calculus are basically screwed, like if i only did further maths and i got asked that question i would be shitting myself. so it really disadvantages those who dont do methods/spesh, hence why i think its pretty stupid how they dont make any mention of differential calculus in the course or straight up allow you to use differentiation or integration in the exam.

also, your method of "deducing" displacement has something to do with the area is clearly arbitrary, and does not work when applying it to the area under a force-displacement graph, which is the work done; there is no obvious link between Newtons (the unit of force) and the work done. Thus, you simply cannot know the area under a velocity-time function is equal to the displacement, without it being explicitly told to you (which it is not in the study design nor in the textbooks), or without having some basic background calculus knowledge, and thus that question has a major flaw, in that it disadvantages those vcaa is trying NOT to disadvantage.
and i never said you need to use calculus for finding the actual area, just that you need calculus knowledge to understand what to do for that specific question.

do you now see why im confused about why they dont let you use calculus?

3 downvotes?! why yall booing me im right

mabajas76

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Re: 2 questions about the physics exam
« Reply #5 on: October 23, 2021, 03:41:24 pm »
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3 downvotes?! why yall booing me im right
A) Never respond to a comment where you have been downvoted and attack the people who downvoted you. It shows ur petty, only care about people agreeing with you and don't understand what ur arguing because your only response to disagreements is " im right"
B) Ashmi has given some very clear and kind replies, as she always does cause she is a legend, on why the course is structured as it is and has succesfully explained your problems. You are literally trying to mansplain physics to somebody doing uni physics and has succesfully completed 3/4 physics, and the stuff you are saying, whilst not neccesarily wrong, is not applicable to what is studied in VCE physics. Prehaps reread what has been said with the VCAA study design and your text book next to you, or maybe some past exams, and carfully consider what your saying, and what purpose it serves before mouthing off.
« Last Edit: October 23, 2021, 03:43:53 pm by mabajas76 »
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Chemistry-It sucks
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"Don't give up, and don't put too much effort into worthless garbage"-Albert Einstein, probably.

Samueliscool223

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Re: 2 questions about the physics exam
« Reply #6 on: October 24, 2021, 05:39:18 pm »
Click here to hide this post again.
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October 24, 2021, 05:39:18 pm - Hidden.
« Last Edit: October 24, 2021, 08:30:57 pm by ashmi »

mabajas76

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Re: 2 questions about the physics exam
« Reply #7 on: October 24, 2021, 10:56:51 pm »
0
Yeah nah bro, I probs know more about VCE physics than this dude, I've gotten 100% for every SAC I've done this year and have been averaging 97 overall practice exams I've done so far. I know my stuff and I know my arguments are correct.
Also, did you even read my comment? Because I never said calculus was directly "applicable" to the current course, I'm saying it SHOULD be because it is necessary to comprehend calculus to do some of the questions. I'm making an argument, not an assertion about the nature of the course.
IDK why I am even bothering to waste my resources trying to reason, so I am leaving. bye.

MOD EDIT: I have fixed your spelling in this post (Capital letters/punctuation to make the post easier to read). Also, a friendly reminder to refrain from trying to start an argument. Your language in the original post violates the rules of respect on the forums, and further posts of this nature will result in consequences.

On a side note, a bit more revision on your conceptual understanding would be ideal to ensure you achieve 97% on the real exam! ;D

(If this thread goes all over the place, it will be locked)


A) Ashmi is a girl and from memory did pretty well in VCE physics. Kinda meh to assume she is a guy just because she understands things better than you.
B) Dude...this website is filled with high achievers. Like...what happned to the other 3% dude? Getting 100% in physics is just...not as impressive as you may think. Obviously not everybody on here gets those grades but this is a safe place, free of judgement. Grades are not everything, they are not a measurment of intelligence nor are they something which should be held as verication that you are a superior person, also some people do things other than study, thats OK!
Honestly I would be more happy if you didn't reply and left your toxicity at the door, u r clearly abit too used to saying really...interesting (I mean stupid but its clear you have an ego) things and everyone just agreeing with you because they either don't get what ur saying(due to its ridiculousness) or don't want you to throw a tantrum. But that isn't going to work here, this isn't reddit. This is a fourm for students to come with actual questions and get answers and advice for anything pertaining to education in Australia.

Also:
You: " Because I never said calculus was directly "applicable" to the current course,"
Also you: " stuff like that requires knowledge of the chain rule "," that requires knowledge of integrational calculus", "requires knowledge of the instantaneous gradient at any given x point, aka the derivative. kids who dont know calculus are basically screwed"
Or in other words, why somebody needs calculus to do the course, which was wrong to begin with but these are your words. YOU are the one saying that calculus is vital to vce physics, and I assure you every VCAA assesor, examinor, 50 student, teacher, high achiever, would disagree with what your saying. Yes calculus is used in physics, but vce physics has not been designed like that.
"Because I never said calculus was directly "applicable" to the current course, I'm saying it SHOULD be because it is necessary to comprehend calculus to do some of the questions."
So essentially, you are saying calculus is directly appliable to the course...You can't say that calculus is neccesary to do the course, then say you are not saying that calculus is applicable to the course.

Anyway remember to thank the MOD for fixing ur spelling :)...also don't be a douche, some of the kids here are crazy smart!

TLDR: This isn't reddit, do your best to grow as a student or gtfo, or at the very elast know what your saying and grades aren't everything ya cocky, entitled bastard.
« Last Edit: October 24, 2021, 11:09:02 pm by mabajas76 »
1 of 2 spec students
Methods student contending with actual genius
Physics, but the comptetion is rather sad.
Chemistry-It sucks
Eng Lan-lol
Religion and Society- Harder than it has a right to be.
"Don't give up, and don't put too much effort into worthless garbage"-Albert Einstein, probably.

insanipi

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Re: 2 questions about the physics exam
« Reply #8 on: October 25, 2021, 09:35:27 am »
+4
A reminder to keep civil, and to refrain from being rude and condescending to users and the board moderator. Respect and kindness are needed, and is the former is clearly outlined in the forum rules which you can find here: https://atarnotes.com/forum/index.php?topic=170369.0

This thread will now be locked as I don't see any productive and/or positive conversation coming out from this thread from this point.
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