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AQA Core 4 - Monday 10th June 2013 (AM) - Official Thread

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For i, you just need to differentiate the expression at the start and replace your function of t for N.

For ii, you just need to find d/dN(dN/dt) and set it equal to zero, solve for N, then solve for t using the original equation.

Thank you

I just have a small question, what happens to the 4000N at the bottom for 7bii)?

Reply 301

rwallace918

Does anyone know where I could find extra questions on vectors because it is the topic I am least confident on?

Reply 302

littleangel9914

Original post by smarties94

Thank you

I just have a small question, what happens to the 4000N at the bottom for 7bii)?

Once you equal dN/dt = 0

you can times both sides by 4000 which will cause the 1/4000 to disappear this is done before you differentiate again

(edited 10 years ago)

Reply 303

Jordn

I Have always thought intergration by inspection was

1/x = ln|x|+c so 1/2x = 2ln|2x| + c

or 3/x = 1/3ln|x| +c

but this mark scheme is telling me differently
have i been taught wrong?

Reply 304

Bord3r

Original post by rwallace918

Does anyone know where I could find extra questions on vectors because it is the topic I am least confident on?

Have you looked at the old spec papers which are basically the same? They have a number of vector questions. They can be found here.

Reply 305

bugsuper

PRSOM for Bord3r - why that got negged is unfathomable

Reply 306

bugsuper

Original post by Jordn

I Have always thought intergration by inspection was

1/x = ln|x|+c so 1/2x = 2ln|2x| + c

or 3/x = 1/3ln|x| +c

but this mark scheme is telling me differently
have i been taught wrong?

I don't think this is quite correct.

When you integrate 1/kx, where k is some constant, the reason you have to put a coefficient in front of your answer is so that, when you integrate it, it's in the form f'(x) / f(x)

for example, integrating 1/2x = integrating 1/2 * 2/2x

2/2x is of the form f'(x) / f(x) - i.e differentiate the denominator and you have the numerator

This means you can use the ln (f(x)) rule on that, so integral of 2/2x = ln 2x

1/2x = 1/2 * integral of 2/2x = 1/2 ln2x

integral of 3/x, as you say, is the same as 3 integral 1/x
so 3lnx

hope it helps

Reply 307

GeorgeL3

Original post by Jordn

I Have always thought intergration by inspection was

1/x = ln|x|+c so 1/2x = 2ln|2x| + c

or 3/x = 1/3ln|x| +c

but this mark scheme is telling me differently
have i been taught wrong?

You can use this as a formula that always works.
Integrating ln.png

Basically whatever is on the bottom goes inside the ln and you divide by it's derivative. If there is a constant there on top it remains as it was.

Reply 308

Bord3r

Original post by bugsuper

PRSOM for Bord3r - why that got negged is unfathomable

Haha thanks but I'm not too bothered. :smile:

Reply 309

FishyTim

Not sure if it has been posted before, but is there anyway I could get my hands on the January 2013 Core 4 paper?

Only teachers can access it from the AQA website, and I wanted to look at it before tomorrow..

Reply 310

Bord3r

Original post by FishyTim

See page 2 of this thread, comment 23. GeneralOJB posted it.

Reply 311

kevloui

Original post by FishyTim

The paper was just bad. It would discourage you.

(edited 10 years ago)

Reply 312

FishyTim

Original post by Bord3r

See page 2 of this thread, comment 23. GeneralOJB posted it.

Thanks so much, (and obviously thanks to GeneralOJB as well)!

Reply 313

stephieg24

does anyone have any tips on forming differential equations from information given? also the grade boundaries for the last two summer c4s have been 51 and 53 which is very low, hopefully this years paper will be similar as i got an a when doing these two papers, also vectors are complete bs to me i just cant visualise them =[

Reply 314

Enginerd.

Can someone tell me the two hardest C4 papers? I want to do them today for last minute practice!

Reply 315

Bord3r

Original post by kevloui

The paper was just bad. It would discourage you.

It was really, really bad. I just did June 07 and it was ridiculously straight forward compared to it. Anyone who says exams have got easier hasn't seen recent AQA maths papers.

Reply 316

bugsuper

The plus side to this is that as the papers have got steadily harder, the grade boundaries have declined.

I don't think this entirely compensates for the increased difficulty of the papers - if you literally don't know how to do a big question, you're going to have problems regardless of how low the grade boundaries are - but it's a little helpful.

Reply 317

The H

Original post by Enginerd.

Can someone tell me the two hardest C4 papers? I want to do them today for last minute practice!

It's personal opinion really but I'd say Jun 12 and Jan 13, but Jun 11 could be up there too

Reply 318

kevloui

Original post by Bord3r

It was really, really bad. I just did June 07 and it was ridiculously straight forward compared to it. Anyone who says exams have got easier hasn't seen recent AQA maths papers.