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Author Topic: dejan91's questions  (Read 17079 times)  Share 

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TonyHem

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Re: dejan91's questions
« Reply #75 on: October 31, 2009, 10:03:55 pm »
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How do you work out H? are u meant to assume that since the graph touches the y-axis at pi/4, it "makes a funnel" there?
Nvm stupid question

If I sub in h = pi/4 into my equation I get
So nope, I haven't got it :/

edit: forget that top as well lol, i took out the 1/2 before squaring it.
« Last Edit: October 31, 2009, 10:13:51 pm by TonyHem »
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Damo17

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Re: dejan91's questions
« Reply #76 on: October 31, 2009, 10:10:19 pm »
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Quote from: dejan91 on October 31, 2009, 09:34:40 pm
The curve formed by the graph of is rotated around the y-axis from to where is a real constant, , to form the shape of a funnel. and are measured in cm. Find,in exact terms, the volume of the funnel for .








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TrueTears

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Re: dejan91's questions
« Reply #77 on: October 31, 2009, 10:11:00 pm »
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Quote from: dejan91 on October 31, 2009, 09:34:40 pm
The curve formed by the graph of is rotated around the y-axis from to where is a real constant, , to form the shape of a funnel. and are measured in cm. Find,in exact terms, the volume of the funnel for .


Volume required

EDIT: damn I got beaten.

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Damo17

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Re: dejan91's questions
« Reply #78 on: October 31, 2009, 10:13:44 pm »
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Quote from: TonyHem on October 31, 2009, 10:03:55 pm
How do you work out H? are u meant to assume that since the graph touches the y-axis at pi/4, it "makes a funnel" there?
If I sub in h = pi/4 into my equation I get
So nope, I haven't got it :/

You most likely took out the from when setting up the integral for volume and forgetting to square it as well. So you would get out the front instead of .
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TonyHem

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Re: dejan91's questions
« Reply #79 on: October 31, 2009, 10:14:29 pm »
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Quote from: Damo17 on October 31, 2009, 10:13:44 pm
Quote from: TonyHem on October 31, 2009, 10:03:55 pm
How do you work out H? are u meant to assume that since the graph touches the y-axis at pi/4, it "makes a funnel" there?
If I sub in h = pi/4 into my equation I get
So nope, I haven't got it :/

You most likely took out the from when setting up the integral for volume and forgetting to square it as well. So you would get out the front instead of .

haha just noticed after msging u
oh wells ;{
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dejan91

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Re: dejan91's questions
« Reply #80 on: October 31, 2009, 10:14:59 pm »
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Why do you let though?
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dejan91

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Re: dejan91's questions
« Reply #81 on: October 31, 2009, 10:16:17 pm »
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Do you just assume that h is at it's maximum value?
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TonyHem

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Re: dejan91's questions
« Reply #82 on: October 31, 2009, 10:17:09 pm »
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It wants the volume for h<pi/4, and h> 0, so the volume from 0 to pi/4
My guess is that you're thinking that it's saying find the volume for some random h that is lower than pi/4
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TrueTears

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Re: dejan91's questions
« Reply #83 on: October 31, 2009, 10:17:11 pm »
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Quote from: dejan91 on October 31, 2009, 10:14:59 pm
Why do you let though?
The question is very very badly worded, look it should really be when

When it says you could actually put any value for h

so yes stupid question. Which exam was this? I remember this question slightly...
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TrueTears

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Re: dejan91's questions
« Reply #84 on: October 31, 2009, 10:17:50 pm »
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Quote from: TonyHem on October 31, 2009, 10:17:09 pm
It wants the volume for h<pi/4, and h> 0, so the volume from 0 to pi/4
My guess is that you're thinking h is an unknown value between 0 to pi/4
When it says find the volume for h < pi/4 , technically you can put any value for h between 0<h<pi/4
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GerrySly

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Re: dejan91's questions
« Reply #85 on: October 31, 2009, 10:18:53 pm »
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Quote from: dejan91 on October 31, 2009, 10:16:17 pm
Do you just assume that h is at it's maximum value?
It's asking for the total volume of the funnel, so the highest height the funnel can be is , therefore the volume of the funnel is achieved when

That's the way I saw it anyway...
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TonyHem

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Re: dejan91's questions
« Reply #86 on: October 31, 2009, 10:21:59 pm »
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Quote from: TrueTears on October 31, 2009, 10:17:50 pm
Quote from: TonyHem on October 31, 2009, 10:17:09 pm
It wants the volume for h<pi/4, and h> 0, so the volume from 0 to pi/4
My guess is that you're thinking h is an unknown value between 0 to pi/4
When it says find the volume for h < pi/4 , technically you can put any value for h between 0<h<pi/4

Hmm... yeah now i'm getting confused.
If I imagine it said h = pi/4, then I would of integrated from 0 to pi/4.
But when I saw that question originally, I was thinking it'll be in terms of H, so when he showed the solution, I was thinking maybe it just means everything under pi/4
:S
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dejan91

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Re: dejan91's questions
« Reply #87 on: October 31, 2009, 10:22:38 pm »
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This was MAV 2008 Exam 2. Yeah It was pretty dodgy wording (I shortened some parts for the forum though). So then if you can technically put in any number under , does that mean there is more than one solution? VCAA wouldn't do that would they?
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TrueTears

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Re: dejan91's questions
« Reply #88 on: October 31, 2009, 10:23:52 pm »
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Quote from: dejan91 on October 31, 2009, 10:22:38 pm
This was MAV 2008 Exam 2. Yeah It was pretty dodgy wording (I shortened some parts for the forum though). So then if you can technically put in any number under , does that mean there is more than one solution? VCAA wouldn't do that would they?
VCAA wouldn't be this ambiguous, MAV is just being a retard. They could have easily said "find the volume of the funnel when h = pi/4" but no...
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dejan91

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Re: dejan91's questions
« Reply #89 on: October 31, 2009, 10:41:11 pm »
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Bastards!

Another one: when a question says "A force of magnitude 10 kg-wt", what does the "kg-wt" mean/stand for?
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