Moment of inertia of Sierpinski carpet

Click For Summary

Homework Help Overview

The discussion revolves around calculating the moment of inertia of a Sierpinski carpet around its center point. The original poster expresses difficulty with the problem and seeks assistance in understanding the relevant concepts and equations.

Discussion Character

  • Exploratory, Assumption checking, Conceptual clarification

Approaches and Questions Raised

  • Participants discuss the use of integrals and analysis methods for solving the problem. There are questions about the specifics of the figure and the implications of the competition rules on discussing solutions. Some participants also share their understanding of the moment of inertia and related equations.

Discussion Status

The conversation includes various interpretations of the problem and the constraints imposed by the competition. Some participants provide insights into the calculations and relationships between different components of the Sierpinski carpet, while others clarify the rules regarding solution sharing.

Contextual Notes

There is mention of a competition, "Olimpiada Fizyczna," which imposes restrictions on discussing solutions publicly before a deadline. Participants are navigating these rules while attempting to understand the problem better.

player1_1_1
Messages
112
Reaction score
0

Homework Statement


Hello
sorry for my english, i know its bad.
The problem i have is to count the moment of inertia of Sierpinski carpet around the point lying in middle of this figure. I would be very thanks to you for solving my problem :)


Homework Equations


i don't know what it mean in english..


The Attempt at a Solution


to use integrals, limes, other analysis methods
 
Physics news on Phys.org
up up
 
what figure?
 
If you are writing "Olimpiada Fizyczna", you shouldn't ask for solution there. If you are not I'll show you the answer in 2 days.
 
what i am writing?
can be in two days, not a problem...
 
but what is a difference if you answer now or in 2 days? :bugeye:
 
I suppose that's the deadline for submitting answers - rules prohibit pariticipants from discussing questions and solutions on public forums earlier.
 
Borek is right.
I don't know English good, so please forgive me mistakes.
"Olimpiada Fizyczna" is some kind of competition in Poland.

If we have big carpet with size 3r and bulk 8m (not 9, because middle of carpet is empty), x is a factor in moment eguation (I don't know how to name it)
I- moment of small carpet (r,m)
I=x*m*r^2
Ic-moment of big carpet 8m,3r
Ic=x*8m*(3r)^2 //I can't prove it, but i know taht it works (from simulation in Excel...)
From Steiner: (http://en.wikipedia.org/wiki/Parallel_axis_theorem)
Ic=4(I+mr^2)+4(I+m(r*2^0,5)^2) //r*2^0,5 is distance from the middle of big carpet to middle of small carpet in corner.
Everything in 4, because we have 4 small carpets next to centre of empty carpet and 4 in corners
first Ic=Ic sceond and for I in second Ic equation we substitute x*m*r^2
and finally we get
x=3/16
 
  • #10
ununbium said:
"Olimpiada Fizyczna" is some kind of competition in Poland.

Physics Olympiad, national level.

equation we substitute x*m*r^2 and finally we get

So once you have explained that I am right you have posted solution two days before the deadline? Am I missing something?

Edit: looks like the deadline was yesterday:

http://www.kgof.edu.pl/

"Termin wysyłania części I" means "deadline to submit 1st part".

So far link to solutions is inactive, perhaps they will be pubslihed on Monday.
 
  • #11
interesting... it is a coincidence anyway :P
thanks for solving this, it took a long time for me to solve it :)
 
  • #12
I wrote 2 days 2 days ago.
Deadline was 15.10.2009 (I am sure), so I think, that i could post the solution.
Am i right?
 
  • #13
Yep, seems everything is OK - hence my edit, I checked details after posting.

Startujesz czy kibicujesz?
 
  • #14
Startuję
 
  • #15
Powodzenia :smile:

Just before Mentors will ban us both - I have asked ununbium if s/he starts or just follows the competition. "Startuję" means "I take part", "powodzenia" means "good luck". That's probably enough Polish for October.
 

Similar threads

  • · Replies 11 ·
Replies
11
Views
1K
  • · Replies 13 ·
Replies
13
Views
3K
Replies
25
Views
2K
  • · Replies 9 ·
Replies
9
Views
3K
  • · Replies 12 ·
Replies
12
Views
2K
  • · Replies 27 ·
Replies
27
Views
5K
  • · Replies 16 ·
Replies
16
Views
2K
  • · Replies 4 ·
Replies
4
Views
4K
  • · Replies 1 ·
Replies
1
Views
1K
  • · Replies 9 ·
Replies
9
Views
2K