Does a circle have a constant rate of change of it self that defines

Click For Summary

Discussion Overview

The discussion revolves around the concept of whether a circle has a constant rate of change that defines its geometric properties. Participants explore the relationship between a line segment and its transformation into a circle, considering aspects of curvature and parameterization.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant questions if a circle has a constant rate of change that defines it, suggesting that every circle is the same regardless of radius, and inquires about the folding of a line segment to form a circle.
  • Another participant mentions that the curvature of a circle of radius r is constant at r-1.
  • A different perspective from differential geometry suggests that while a circle can be traced at constant speed, there are infinitely many parameterizations, some of which may not maintain constant speed or smoothness.
  • A participant reiterates the initial question about the rate of change needed for a line segment to fold into a circle and introduces a polar coordinate definition of a circle where the radius does not change with respect to the angle.
  • Another participant notes that defining a circle requires specifying its radius and center point, providing the standard equation of a circle.

Areas of Agreement / Disagreement

Participants express varying interpretations of the concept of constant rate of change in relation to circles. There is no consensus on whether a circle can be defined by a constant rate of change, and multiple perspectives on parameterization and curvature are presented.

Contextual Notes

Some discussions involve assumptions about the definitions of curvature and parameterization, and the implications of these definitions on the characterization of circles. The exploration of polar coordinates introduces additional complexity to the discussion.

MotoPayton
Messages
96
Reaction score
0
Does a circle have a constant rate of change of it self that defines it as a circle.
I have never heard of such a thing but I am curious. It must right??

Since every circle is the same no matter the radius(the arch will change by some constant amount per radian)

If that doesn't make sense.. I am asking by how much does some line segment need to fold onto itself to form a perfect circle. What will be the rate of change of that line segment to form a perfect circle and with respect to what variable??
 
Physics news on Phys.org


I'm not quite sure what you're asking, but the curvature of a circle of radius r is the constant r-1.
 


A differential geometry perspective.

Sooo... I'm not entirely sure if this will help, but I think that the answer to the "constant speed question" is not necesarily. Idealy we could make the circle be traced out at constant speed.

Here is how i think of it.
C:[0,1] --> S1
S1 will be the circle as a subset of the plane.
We can make
C=(cos(t),sin(t))

this takes the first point of the line, and then puts it at the (1,0) point on the circle. Every other point is then curled to follow the tangent vector (-sin(t), cos(t) ).
that gives us a "constant rate".

Now it may be shown that there are probably infinitely many other paramaterizations of a circle, and some analytic geometry will show that you could define circles that don't have constant speed paramaterizations, in fact you could paramaterize it to not be "smooth".

I hope this helps, but I now think maybe you were asking if there is a way to characterize the circle as a "curling" of the line?
 


MotoPayton said:
Does a circle have a constant rate of change of it self that defines it as a circle.
I have never heard of such a thing but I am curious. It must right??

Since every circle is the same no matter the radius(the arch will change by some constant amount per radian)

If that doesn't make sense.. I am asking by how much does some line segment need to fold onto itself to form a perfect circle. What will be the rate of change of that line segment to form a perfect circle and with respect to what variable??

You can define a circle in polar coordinates by

[tex]\frac{dr(\theta)}{d\theta} = 0[/tex]
with [itex]r(\theta_0) = R \neq 0[/itex]. i.e., the radius of the curve does not change with theta, and you know that r for some value of theta is a non-zero number.
 


To get the equation of the circle, requirements are radius and center point right..??
(x-h)^2-(y-k)^2=r^2
 

Similar threads

  • · Replies 9 ·
Replies
9
Views
1K
  • · Replies 5 ·
Replies
5
Views
8K
  • · Replies 21 ·
Replies
21
Views
12K
Replies
1
Views
6K
  • · Replies 13 ·
Replies
13
Views
2K
  • · Replies 7 ·
Replies
7
Views
3K
  • · Replies 6 ·
Replies
6
Views
3K
  • · Replies 2 ·
Replies
2
Views
4K
  • · Replies 36 ·
2
Replies
36
Views
4K
Replies
60
Views
5K