VCE Specialist 3/4 Question Thread!

[Shadowxo]

Would really appreciate it if someone could explain how to find the range of the following functions by hand: 

f(x)=(1/3)^2x-x2
f(x)=(1/3)^x2-2x

Thanks in advance!

For the first one:
as x-> infinity and x-> negative infinity, 2x-x² -> negative infinity
As  2x-x² -> negative infinity, f(x)-> infinity (as 1/3 is less than 1)
maximum value of 2x-x² occurs when d/dx(2x-x²)=0
2-2x=0, x=1
So minimum value of f(x)=1/3¹
Range: [1/3 , infinity)

Similar method for the second question

[peterpiper]

Can someone help me on question 4d) -- I tried using the vector formula (|a||b|cos(theta) = a.b) but couldn't put it in terms of pi. Is there another way to approach this question?

Thanks!

[VanillaRice]

Can someone help me on question 4d) -- I tried using the vector formula (|a||b|cos(theta) = a.b) but couldn't put it in terms of pi. Is there another way to approach this question?

Thanks!

I would say that your approach is the way I would go about it. So when using the vector formula you mentioned (assuming you can use your calc):

Spoiler

Solve for theta in degrees (calc):



Convert to radians:

[peterpiper]

I would say that your approach is the way I would go about it. So when using the vector formula you mentioned (assuming you can use your calc):

Spoiler

Solve for theta in degrees (calc):



Convert to radians:

Thank you! :^)

Also (sorry again): I'm having trouble working out what is required of me for question (b) and (c). Like how do I work out my Friction if my N value is kinda dependent on the T value? Much confusion. Any help would be great!

Thanks again guys!

[Shadowxo]

Thank you! :^)

Also (sorry again): I'm having trouble working out what is required of me for question (b) and (c). Like how do I work out my Friction if my N value is kinda dependent on the T value? Much confusion. Any help would be great!

Thanks again guys!

Hi
So for b) you know that N+Tsin30=W (as net force=0). So the maximum T value for the crate to not be lifted from the floor occurs when N=0 (ie all the upwards force is being applied by the tension). From there should be easy
c) So N=W-Tsin30. Fr=uN=u(W-Tsin30). Weight is constant so now you should be able to solve for T
Hope this helps

[peanut]

Can someone please explain the answers for question b and c? Why is the slope field only graphed for x = -2? I have a feeling that these solutions are completely wrong...

[Sine]

Can someone please explain the answers for question b and c? Why is the slope field only graphed for x = -2? I have a feeling that these solutions are completely wrong...

from what I see the solutions are completely wrong

for part c you will need to use the slope field that should've been generated in part b) to help you sketch it

[Jovan Vales]

do you have to do spesh 12 to do spesh 34, or methods 34 enough. trying to work out a vce plan

[Sine]

do you have to do spesh 12 to do spesh 34, or methods 34 enough. trying to work out a vce plan

According to the study design these are the possible combinations (see attatchment)

I still think you can do 3/4 stuff without actually doing the 1/2 units although it would take extra work outside of school.

[Shadowxo]

do you have to do spesh 12 to do spesh 34, or methods 34 enough. trying to work out a vce plan

If you want to do spesh 3/4 without 1/2, you could certainly do it but I would strongly recommend you do plenty of extra work during holidays / term time before starting 3/4. I found when I did it, it had quite different content to methods (spesh had complex/imaginary numbers, vectors and other things not present in methods). 3/4 Also did draw on a lot of 1/2 knowledge so you'd need to get familiar with the basics and be willing to put in the extra work for 3/4. Maybe contact a spesh teacher and see if you could get some worksheets / questions / tests for 1/2 content relevant for 3/4 to get familiar with it.

If you're in year 10 trying to figure out a plan for year 11 and 12, I would strongly recommend doing 1/2 spesh if you intend on 3/4. It is a subject that requires you to have a reasonable amount of experience with the 1/2 content before you start 3/4 (in my opinion). Some other subjects don't rely on earlier content as much and so I'd recommend going straight to 3/4 for one of these subjects instead.

Tl;dr you can do 3/4 it without 1/2 but you'll have to put in the extra work.

Good luck in your choices and feel free to ask for any more advice

[Gogo14]

Someone give me a really challenging question that can be done with vce knowledge!

[MightyBeh]

Someone give me a really challenging question that can be done with vce knowledge!

This thread has some that are worth a try even if they are a bit old.

[smiley123]

For the acceleration-time graph that I have attached, how do I calculate the final displacement using: Method1- constant acceleration rules and Method 2-intergration? Initial position and velocity are 12m and 3m/s respectively.

[keltingmeith]

For the acceleration-time graph that I have attached, how do I calculate the final displacement using: Method1- constant acceleration rules and Method 2-intergration? Initial position and velocity are 12m and 3m/s respectively.

For both methods, you're going to need to split it up into three parts - the first positive bit, the negative bit, and the second positive bit. Remember that displacement is a vector quantity, and then add them all up in the end. Let us know what answer you get/how you got it if, after trying that, you arrive at the wrong answer.

[smiley123]

For both methods, you're going to need to split it up into three parts - the first positive bit, the negative bit, and the second positive bit. Remember that displacement is a vector quantity, and then add them all up in the end. Let us know what answer you get/how you got it if, after trying that, you arrive at the wrong answer.

I've tried both methods but keep getting the wrong answer. For method 1 I used s=ut+1/2at^2 to find each displacement. I used the final velocity of the previous part as the initial velocity of the next.
For method 2 I think I am subbing in the wrong values. For the integration of second part velocity function I subbed t=0 and v=7 into v=-t+c.