VCE Specialist 3/4 Question Thread!

[M_BONG]

Has anyone done MAV Exam 2, 2011?

Thoughts? Because I got absolutely wrecked. 10/10 difficulty. Hardest exam I have done so far, lol MC took me 40 minutes (avg 25 mins) alone.

[Zealous]

Find all roots of the equation in the form a + bi

Can someone please help me with this question?

Then solve each equation for z and you'll get four solutions for z. If you were to do it by hand, you'd convert it to polar, take the square roots then convert it back to cartesian; however the numbers are pretty messy so if its a CAS question you're better off solving from here on the CAS (or even at the beginning =p).

Has anyone done MAV Exam 2, 2011?

Soon... I did MAV 2010 like last week. I'll get back to you once I've done it.

[psyxwar]

Has anyone done MAV Exam 2, 2011?

Thoughts? Because I got absolutely wrecked. 10/10 difficulty. Hardest exam I have done so far, lol MC took me 40 minutes (avg 25 mins) alone.

MC takes you 25 min? O___O crap I'm taking too long then, I usually spend like 35min on MC @__@

[M_BONG]

Guys, I really suck at Mechanics because I have no background knowledge, so I might be asking a really basic question.

In a mass, when you are finding the resultant force, do you take into account the tension or not?

Ie. If you have the forces, and you have the total mass and you need to find acceleration, is tension in the string connected to the two particles a variable in resultant force?

I did this question and they didn't include tension in the strings as part of the resultant force?

MC takes you 25 min? O___O crap I'm taking too long then, I usually spend like 35min on MC @__@

Yeah but I have been doing the less challenging exams up until now (ie. Heffernan, TSSM, Insight) but they're still pretty hard. When I get to 25 mins, I just stop doing MC (usually only have one or two left) and move on and come back if I have time.

But I think I am taking too fast because if you divide total mark on paper 2 by total time, you should be spending 33 minutes on MC.

Soon... I did MAV 2010 like last week. I'll get back to you once I've done it.

How'd did you find MAV 2010? I am also moving up by years with MAV, and did it yesterday.  I found it to be on VCAA standard (not ridiculously difficult or anything).

[lzxnl]

MC takes you 25 min? O___O crap I'm taking too long then, I usually spend like 35min on MC @__@

Yeah 35 min is a bit long. I normally aimed to have them done by about 20-25 min too.

35-40 min is how long it took me to do MC sections in Kilbaha exams LOL

This is what you do for mechanics questions. If the force affects the object's movement, you count it as part of the resultant force. Tension normally does that. Sometimes, they say the string is 'loose', in which the tension is zero.

[allstar]

a; convert to polar form, then take the root, then convert back to cartesian form.

b;i)use discriminant = b^2-4ac
ii) I think this is just the quadratic formula? It seems like the term in the discriminant is what you got in part a), so using part a you can find out the expression for the sqrt(discriminant) in Cartesian form which lets you solve the equation nicely for the roots.

what did you mean by take the square root of the polar form?

[psyxwar]

Yeah 35 min is a bit long. I normally aimed to have them done by about 20-25 min too.

35-40 min is how long it took me to do MC sections in Kilbaha exams LOL

This is what you do for mechanics questions. If the force affects the object's movement, you count it as part of the resultant force. Tension normally does that. Sometimes, they say the string is 'loose', in which the tension is zero.

ohh maybe cuz the last one I did was Kilbaha and that threw my timing off lol. I still take about 30 min I reckon so I'll try and cut down on that

Can someone have a look and see if I'm showing enough working? The question is worth 6 marks (from Kilbaha Exam 2 2009) and they provided a whole page. My answers are right but I'm not sure if I should show more working? The mass of the particle is 9kg btw.

what did you mean by take the square root of the polar form?

Find the polar form of the thing underneath the sqrt, then using demoivre's theorem find what the square root is.

[M_BONG]

Yeah 35 min is a bit long. I normally aimed to have them done by about 20-25 min too.

35-40 min is how long it took me to do MC sections in Kilbaha exams LOL

This is what you do for mechanics questions. If the force affects the object's movement, you count it as part of the resultant force. Tension normally does that. Sometimes, they say the string is 'loose', in which the tension is zero.

It didn't say loose, but it said "light inextensible string" = same thing?

But after they didn't consider tension in the resultant force equation. They made me find the magnitude of tension? Why do that?

Actually here's part of the question.

[nhmn0301]

Can someone have a look and see if I'm showing enough working? The question is worth 6 marks (from Kilbaha Exam 2 2009) and they provided a whole page. My answers are right but I'm not sure if I should show more working? The mass of the particle is 9kg btw.

Maybe try to see the mark allocation in the answer to figure out where they will give you the mark? Otherwise I think just jot down a few lines of where you get the forces from (i.e in the i direction or j direction), show the steps of adding the equations or any necessary transposition .

It didn't say loose, but it said "light inextensible string" = same thing?

But after they didn't consider tension in the resultant force equation. They made me find the magnitude of tension? Why do that?

Actually here's part of the question.

I think "light inextensible string" here doesn't mean there is no tension, it means that "light = weight of the string is negligible", "inextensible= this string is not stretchy". Since if a string is stretchy, the tension might be different according its stretchiness and as far as I'm aware, stretchy string is not examinable so they might tell you the string cannot be stretched or in the case of pulleys, they will tell you the pulley is smooth (assuming no friction).
They do consider the tension in the resultant equation, it's just that they cannel out each other (since given we have the same string, the tension force on both car and truck shall be the same but just in opposite direction).
Truck: 4000 - 1200 - T = 2200a  => T = 2800 - 2200a
Car:  T - 600 = 1000a   => T = 1000a + 600.
T is the same for both particles, and you can see tension is taken into account from there.
My Physics knowledge is very limited so please correct me if I'm wrong....

[lzxnl]

The reason why they say 'inextensible' is, as nhmn0301 points out, because the tension of a stretched string depends on how much it is stretched and that would be a dodgy question to ask VCE students. VCE only deals with light inextensible strings.

[LiquidPaperz]

how disadvantaged will i be when doing spesh 3/4 next year without physics?

is it something that will take me long to grasp?

[psyxwar]

how disadvantaged will i be when doing spesh 3/4 next year without physics?

is it something that will take me long to grasp?

You'll be fine, the physics in specialist is pretty basic (though arguably, the physics in VCE physics is pretty basic...). It might take you a bit longer than the physics kids to grasp the concepts at the start, but yeah it's not a huge issue. I didn't do physics either.

[lzxnl]

You'll be fine, the physics in specialist is pretty basic (though arguably, the physics in VCE physics is pretty basic...). It might take you a bit longer than the physics kids to grasp the concepts at the start, but yeah it's not a huge issue. I didn't do physics either.

I learnt spesh before I did any physics and the mechanics bit made the least sense by far. It'll certainly be a bit of a struggle but it's quite doable.

[silverpixeli]

how disadvantaged will i be when doing spesh 3/4 next year without physics?

is it something that will take me long to grasp?

Disclaimer: I did physics before studying mechanics in spesh

I think it's doable without physics background, you'll just have a few concepts to get your head around first (mainly newton's laws and how they apply to situations, and the relationship between displacement/velocity/accel. ) which physics students would already be familiar with

Not that it assumes background, but the textbook doesn't spend much time on these physics concepts because it's not the focus of the chapter (the focus is the spesh stuff, i.e. the applications), there's nothing stopping you from consulting khanacademy or another free resource that covers the foundational physics concepts of motion and forces, it shouldnt take much extra time and will set you up to understand the mechanics sections a little better going into them

[keltingmeith]

I did not do physics.
I nearly failed year 12 level physics at uni last semester.
I got full marks on the mechanics section of my exam.

You'll be absolutely fine for specialist without physics, you just need to put in an extra effort compared to those who are doing/done physics.