VCE Specialist 3/4 Question Thread!

[allstar]

help with the VCAA 2011 exam 2 q5e)
why did they take the limits between 0 - 10, when the graph is drawn in the previous part? the volume has been continually increasin until t = 8.3 thats when it starts to drop so if i wanna find the amount of chemical FLOWED OUT shouldn't i be taking the limits between 8.3 and 10?

thank you

[Soon]

help with the VCAA 2011 exam 2 q5e)
why did they take the limits between 0 - 10, when the graph is drawn in the previous part? the volume has been continually increasin until t = 8.3 thats when it starts to drop so if i wanna find the amount of chemical FLOWED OUT shouldn't i be taking the limits between 8.3 and 10?

thank you

I think it's because for any time t>0, there is chemical flowing both in and out. So even though the amount of chemical in the tank after t=8.3 is decreasing, there is still chemical flowing out represented by x/(1+t) in part b) if that makes sense!

[Mieow]

Can someone please help me with question 3 and 4.

For question 4 i tried drawing triangles and using the double-angle formula but it got too messy. 

[lucas.vang]

I started with the the sec (pi/5)
I have no clue how to use the maths symbols so bare with me.

sec(pi/5) = 1/cos(pi/5)

1/cos(pi/5) can be written as 1/cos(2 x pi/10)

* cos (2 x pi/10) ~ Cos (2 theta) .... so cos (2 x pi/10) can equal 1 - 2 sin^2 (pi/10)

given the rule cos(2 theta) = 1 - 2sin^2(theta)

therefore 1/cos(2 x pi/5) = 1/(1-2sin^2(pi/10))   and then you have sin(pi/10) so sub it in.

[allstar]

thank you soon!

another vcaa question?
VCAA 2012 exam 1 q4b?
how did they get T = 100g - 2N?

[eagles]

VCAA 2011 Exam 1- question 7.

Why is the highlighted method incorrect?

[bts]

HELLO!!!!

with graphs of hyperbolas, how do you know whether its both branches or only one branch that needs to be drawn, when no domain is given?

[allstar]

where did the 2N come from?

[chrae9]

HELLO!!!!

with graphs of hyperbolas, how do you know whether its both branches or only one branch that needs to be drawn, when no domain is given?

It will be both branches drawn if there is no domain.
However in most cases if it's parametric equations x(t) and y(t) the domain will be limited by the domain of (t).
In this case:
- the domain = range of x(t) over domain of t
- the range = range of y(t) over domain of t

hope this helps

[chickenfries]

i have a antidif question:

how would I solve that? to find v in terms of x?

d[(1/2)v^2)]/dx = 4v^3 +2v^2 - 3

[yang_dong]

part b please?

[eagles]

part b please?

See attached.

(Factorise the 1/4 out from the surd)


- Can someone explain when to use 'N' and when to use 'R' on force diagrams? Thanks.

[lzxnl]

i have a antidif question:

how would I solve that? to find v in terms of x?

d[(1/2)v^2)]/dx = 4v^3 +2v^2 - 3

You wouldn't deal with that actually.
Rather, you have d(1/2 ^2)/dx = v dv/dx = 4v^3 + 2v^2 - 3
dv/dx = (4v^3 + 2v^2 - 3)/v
dx/dv = v/(4v^3 + 2v^2 - 3)
And here, I can only say...good luck integrating this as you can't actually factor the bottom.

[Bestie]

can someone please help me here:

to prove that ABCD is a parallelogram, what else do i need to prove besides from mag AB = mag DC and mag AD = mag BC something about the diagonals bisect at right angles, but then that wouldn't nesscarily be a parallegram its a rhombus?

how come the ans says i just need to prove vector AB = DC? but they are supposed to be at diffrent positions, so they can be the same vector, instead should have the same mag?

thank you

[lolalol]

can someone please help me here:

to prove that ABCD is a parallelogram, what else do i need to prove besides from mag AB = mag DC and mag AD = mag BC something about the diagonals bisect at right angles, but then that wouldn't nesscarily be a parallegram its a rhombus?

how come the ans says i just need to prove vector AB = DC? but they are supposed to be at diffrent positions, so they can be the same vector, instead should have the same mag?

thank you

By proving AB=DC you're basically showing that they're not only the same length but they're parallel

EDIT: Also they wouldn't be the same vector in the same place if they've given you the coordinates of A, B, C, and D and A and D are in different places.