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Type: Posts; User: bleakarcher

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1. ## Thread: HSC 2013 4U Marathon

by bleakarcher
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1,663
Views
47,619

### Re: HSC 2013 4U Marathon

lol, there's something else wrong with my attempt.
2. ## Thread: HSC 2013 4U Marathon

by bleakarcher
Replies
1,663
Views
47,619

### Re: HSC 2013 4U Marathon

Well, at the time that I wrote the solution I rushed and thought that too. On second thought, how could f '(x+f(x))=[1+f '(x)]*f '(x+f(x) and f '(x+f(x))=f '(x)?
3. ## Thread: HSC 2013 4U Marathon

by bleakarcher
Replies
1,663
Views
47,619

### Re: HSC 2013 4U Marathon

Yeah, that's why I wasn't sure about it. Pretty sure it's wrong now.
4. ## Thread: HSC 2013 4U Marathon

by bleakarcher
Replies
1,663
Views
47,619

### Re: HSC 2013 4U Marathon

Think it works dude, nice. I'm not so sure about my method though:

f(x)=f(x+f(x))
f '(x)=[1+f '(x)]*f '(x+f(x))=[1+f '(x)]*f '(x) => f '(x)=0 for all x. Since f(x) is continuous and...
5. ## Thread: HSC 2013 4U Marathon

by bleakarcher
Replies
1,663
Views
47,619

### Re: HSC 2013 4U Marathon

Hey guys, here's a question from last year's UNSW maths competition. Let f(x) denote a strictly positive continuous function defined on all real numbers with the property that f(2012)=2012 and...
6. ## Thread: HSC 2013 4U Marathon

by bleakarcher
Replies
1,663
Views
47,619

### Re: HSC 2013 4U Marathon

Did it. ^ That happened.
7. ## Thread: HSC 2013 4U Marathon

by bleakarcher
Replies
1,663
Views
47,619

\int x^3
8. ## Thread: HSC 2013 4U Marathon

by bleakarcher
Replies
1,663
Views
47,619

### Re: HSC 2013 4U Marathon

1) [(1/a)-(1/b)]^2 + [(1/a)-(1/c)]^2 + [(1/b)-(1/c)]^2 >=0 (equality occurs iff a=b=c)
2/a^2 + 2/b^2 + 2/c^2 -2[(1/ab)+(1/bc)+(1/ac)] >=0
=> (1/a)^2 + (1/b)^2 + (1/c)^2 >= 1/bc + 1/ac + 1/ab for...

by bleakarcher
Replies
742
Views
19,350

### Important:Re: Year 12 2013 Chit Chat Thread

It's fine lol.

by bleakarcher
Replies
742
Views
19,350

### Important:Re: Year 12 2013 Chit Chat Thread

How so?

by bleakarcher
Replies
742
Views
19,350

### Important:Re: Year 12 2013 Chit Chat Thread

Was that in an exam bro? I think you mean (-1/4) not (-1/8).
12. ## Thread: MX2 Integration Marathon

by bleakarcher
Replies
525
Views
13,217

13. ## Thread: 2013 Half Yearlies?

by bleakarcher
Replies
39
Views
1,645

### Re: 2013 Half Yearlies?

3U Maths - 99% (1st)
4U Maths - 99% (1st)
Physics - 83% (2nd, highest was 87%)
Chemistry - 97% (1st)
English - Haven't gotten my final mark yet
14. ## Thread: HSC Physics Marathon

by bleakarcher
Replies
93
Views
2,811

### Important:Re: HSC Physics Marathon

When the motor of an electric drill is experiencing a load, its rotational speed lowers which in turn lowers the back EMF of the motor. Net EMF = Supply EMF - Back EMF. If the back EMF is decreased,...

by bleakarcher
Replies
54
Views
1,213

Thanks for that man, appreciate it. Just one final thing, what's wrong with this? There must be something wrong with the direction of the induced magnetic field but it's not clear to me.

28045
16. ## Thread: HSC 2013 4U Marathon

by bleakarcher
Replies
1,663
Views
47,619

### Re: HSC 2013 4U Marathon

By symmetry, it's just pi*r^2*H/4

by bleakarcher
Replies
54
Views
1,213

I get what you're saying man but do you mind explaining how you could deduce it using the right hand grip rule? I tried using that and got a result that violated the law of conservation of energy lol.

by bleakarcher
Replies
54
Views
1,213

Here's what I was thinking. Since when t=0, V=0, the plane would initially be perpendicular to the direction of the magnetic field. If you turned it clockwise or anti-clockwise, the induced current...

by bleakarcher
Replies
54
Views
1,213

So that means current flows in the opposite direction if turned anti-clockwise, right?

by bleakarcher
Replies
54
Views
1,213

Yes, I agree but DC in the external circuit. The question says 'Which graph below best represents the EMF induced in the coils after the changes were made?', not the external circuit. The current...

by bleakarcher
Replies
7
Views
435

### Curious.

If someone in second place is behind first by about 2% by the time all internal assessments are over and this person performs better externally than the person ranked first, who gets the better final...

by bleakarcher
Replies
54
Views
1,213

Thinking about it again actually, I think it's A (call me crazy). I don't think either changes would cause a change in the V-t graph.

by bleakarcher
Replies
54
Views
1,213

With q11), since it says the EMF induced in the coils, wouldn't the correct answer be B? I'm thinking it would be D if you're talking about the EMF in the external circuit.

by bleakarcher
Replies
8
Views
242

### Re: Permutation help!!!

The balls have to be in different colours though i.e. one must be white, one must be yellow and one must be purple. So wouldn't it be 3!=6?
25. ## Thread: HSC 2013 4U Marathon

by bleakarcher
Replies
1,663
Views
47,619

### Re: HSC 2013 4U Marathon

Yeah, both are correct expressions for the primitive.
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