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March 29, 2024, 03:33:56 pm

Author Topic: 3U Maths Question Thread  (Read 1230515 times)  Share 

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amandali

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Re: 3U Maths Question Thread
« Reply #195 on: June 12, 2016, 02:49:28 am »
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for part c ii)  i dont get how the last constant becomes (pCp)(qCp)

RuiAce

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Re: 3U Maths Question Thread
« Reply #196 on: June 12, 2016, 08:08:01 am »
+3
(Image removed from quote.)(Image removed from quote.)

for part c ii)  i dont get how the last constant becomes (pCp)(qCp)

This is because you stopped at the wrong term in the last term.

You stopped at pCp (xp) * qCq (1/x)q

But this is not a constant term. This results in xp-q which doesn't necessarily equal to xp-p!


Because p≤q, you must stop at pCp (xp) * qCp (1/x)p = (pCp)(qCp)x0
(as you don't know if p<q or p=q)

To view this, consider a simple example where p=2 and q=3. Clearly, when p=2 and q=3, the last term is not a constant term
« Last Edit: June 12, 2016, 08:10:01 am by RuiAce »

amandali

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Re: 3U Maths Question Thread
« Reply #197 on: June 12, 2016, 03:15:00 pm »
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for part b)   what is the reason that the velocity is negative

i dont understand part c)iii)   ive attached the answer it below


RuiAce

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Re: 3U Maths Question Thread
« Reply #198 on: June 12, 2016, 03:24:11 pm »
+1
for part b)   what is the reason that the velocity is negative

i dont understand part c)iii)   ive attached the answer it below





That is the reason. To satisfy v=1, not v=-1.

RuiAce

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Re: 3U Maths Question Thread
« Reply #199 on: June 12, 2016, 03:40:52 pm »
+4
for part b)   what is the reason that the velocity is negative

i dont understand part c)iii)   ive attached the answer it below









This was a nice question. I recalled it from the 2015 paper, because I remember asking my colleagues how they went. This is my first time actually doing the question though.

Tell me if something makes no sense.
« Last Edit: June 12, 2016, 03:45:41 pm by RuiAce »

IkeaandOfficeworks

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Re: 3U Maths Question Thread
« Reply #200 on: June 13, 2016, 03:44:47 pm »
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Hey guys! can you help me with these motion questions?  Thank you!


RuiAce

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Re: 3U Maths Question Thread
« Reply #201 on: June 13, 2016, 03:54:13 pm »
+1
Hey guys! can you help me with these motion questions?  Thank you!



RuiAce

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Re: 3U Maths Question Thread
« Reply #202 on: June 13, 2016, 03:59:24 pm »
+1
Hey guys! can you help me with these motion questions?  Thank you!





amandali

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Re: 3U Maths Question Thread
« Reply #203 on: June 13, 2016, 04:37:54 pm »
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i did integration and got stucked

jakesilove

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Re: 3U Maths Question Thread
« Reply #204 on: June 13, 2016, 05:11:16 pm »
+1
i did integration and got stucked

Hey Amandali!

I've attached the solution before. Using a method like this is pretty standard, however usually in the 3U course they lead your through it a bit more. Still, if you ever get a question like this, just think about what you are TRYING to prove and basically brute-force your way there!

Sorry that it's hand written; Rui and Jamon still haven't taught me LaTeX.



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RuiAce

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Re: 3U Maths Question Thread
« Reply #205 on: June 13, 2016, 05:12:41 pm »
+1
i did integration and got stucked



If you're interested in why it's mathematically incorrect, it's because well an assumption is being made that the sum goes to infinity.




Oops: Got a message saying that a reply was already posted. So I'll leave this working out here and leave the remainder of the question for you to try out

RuiAce

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Re: 3U Maths Question Thread
« Reply #206 on: June 13, 2016, 05:14:07 pm »
+1

Sorry that it's hand written; Rui and Jamon still haven't taught me LaTeX.


Oi. I read this :P


jakesilove

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Re: 3U Maths Question Thread
« Reply #207 on: June 13, 2016, 05:17:13 pm »
+1
Oi. I read this :P

That was the idea  ;)
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RuiAce

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Re: 3U Maths Question Thread
« Reply #208 on: June 13, 2016, 05:17:39 pm »
+2
That was the idea  ;)

Well it's not my fault that we all have exams :P

RuiAce

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Re: 3U Maths Question Thread
« Reply #209 on: June 13, 2016, 06:27:08 pm »
+1
Hey Amandali!

I've attached the solution before. Using a method like this is pretty standard, however usually in the 3U course they lead your through it a bit more. Still, if you ever get a question like this, just think about what you are TRYING to prove and basically brute-force your way there!

Sorry that it's hand written; Rui and Jamon still haven't taught me LaTeX.

(Image removed from quote.)

Jake

Oh wait, slight correction after looking at this again

You forgot the (annoying) +C when integrating

(The final answer is unaffected though because when you subtract the two resultant equations, the C cancels out)