LinuxQuestions.org
Help answer threads with 0 replies.
Go Back   LinuxQuestions.org > Forums > Non-*NIX Forums > General
User Name
Password
General This forum is for non-technical general discussion which can include both Linux and non-Linux topics. Have fun!

Notices

Reply
 
Search this Thread
Old 11-11-2004, 08:10 AM   #1
Mathiasdm
LQ Newbie
 
Registered: Aug 2004
Distribution: Ubuntu Gutsy Gibbon
Posts: 25

Rep: Reputation: 15
And some maths :-P


Well, I'm sorry to bother you all with this exercise, but I can't seem to find the solution.

First of all: no, this is NOT a homework, it's just an exercise in our book, and I'm curious as to what the solution is. I've been trying to find it for over an hour straight, and I just can't figure it out.


A man starts to walk in point P and walks around a circular lake (radius: 3.2 km) with a constant speed of 4.8 km/hour. The position of the man is R.
How fast does the length of the cord PR change, when PR = 60?

Oh, and we saw this exercise with Derivatives, just mentioning ;-)
Anyone care to try?
 
Old 11-11-2004, 08:56 AM   #2
vharishankar
Senior Member
 
Registered: Dec 2003
Posts: 3,142
Blog Entries: 4

Rep: Reputation: 121Reputation: 121
Can you post a link to a diagram of this problem, if possible?
 
Old 11-11-2004, 09:08 AM   #3
Andrew Benton
Senior Member
 
Registered: Aug 2003
Location: Birkenhead/Britain
Distribution: Linux From Scratch
Posts: 2,073

Rep: Reputation: 64
Or you could tell us where is. The angle PR is meaningless if you don't define . If is the centre of the lake the length of the cord PR changes at 4.8*sin60=4.157km/hour when PR = 60

Last edited by Andrew Benton; 11-11-2004 at 09:09 AM.
 
Old 11-11-2004, 09:27 AM   #4
Mathiasdm
LQ Newbie
 
Registered: Aug 2004
Distribution: Ubuntu Gutsy Gibbon
Posts: 25

Original Poster
Rep: Reputation: 15
Oh, oops.
Yes, is the centre of the lake.
Sorry!
Could you explain your answer too?
 
Old 11-11-2004, 09:43 AM   #5
kees-jan
Member
 
Registered: Sep 2004
Distribution: Debian, Ubuntu, BeatrIX, OpenWRT
Posts: 273

Rep: Reputation: 30
Explaining the answer would either involve a bunch of formulas (if you want calculus and derivatives used in the explanation) or a bunch of drawings (if you want an explanation using vector analysis), both of which are most easily provided by sitting at a desk with you.

Maybe you can make our lives a little easier by explaining what you are trying to do and how far you've got?

Thanks!

Groetjes,

Kees-Jan
 
Old 11-11-2004, 09:57 AM   #6
Mathiasdm
LQ Newbie
 
Registered: Aug 2004
Distribution: Ubuntu Gutsy Gibbon
Posts: 25

Original Poster
Rep: Reputation: 15
Well, I'm trying to calculate it using calculus and derivatives.
I'm sorry for bothering you all with this, and I feel rather stupid asking this question (normally, I don't have any problems calculating derivatives).

Here's a picture:
http://img.photobucket.com/albums/v1...ol/picture.jpg
 
Old 11-11-2004, 10:16 AM   #7
kees-jan
Member
 
Registered: Sep 2004
Distribution: Debian, Ubuntu, BeatrIX, OpenWRT
Posts: 273

Rep: Reputation: 30
Well, then. The length of a can be found using the cosine rule (using the angle POR). POR itself is a function of radus r, velocity v and time t.

You can then compute the derivative of a using the chain rule (twice, I think).

Where exactly do you get stuck?

Groetjes,

Kees-Jan

PS. You are pushing "general" to its limit, aren't you :-)
 
Old 11-11-2004, 03:48 PM   #8
Mathiasdm
LQ Newbie
 
Registered: Aug 2004
Distribution: Ubuntu Gutsy Gibbon
Posts: 25

Original Poster
Rep: Reputation: 15
Silly me! I didn't think about the cosine rule ops:
I understand it now :-)
Thanks!

PS. Yes, I know :-P
 
  


Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is Off
HTML code is Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
childrens learning ie maths master Linux - General 2 07-09-2005 02:43 PM
Suggestions for Maths Software andrewlkho Linux - Software 3 04-11-2005 09:44 PM
please help me do maths :) darkRoom General 36 04-11-2005 01:03 PM
problem with maths redduck666 General 7 02-12-2005 02:33 PM
java + maths problem craddy Programming 2 03-04-2004 02:23 PM


All times are GMT -5. The time now is 06:14 PM.

Main Menu
My LQ
Write for LQ
LinuxQuestions.org is looking for people interested in writing Editorials, Articles, Reviews, and more. If you'd like to contribute content, let us know.
Main Menu
Syndicate
RSS1  Latest Threads
RSS1  LQ News
Twitter: @linuxquestions
identi.ca: @linuxquestions
Facebook: linuxquestions Google+: linuxquestions
Open Source Consulting | Domain Registration