Curvature in terms of the tangent vector

In summary, the conversation discusses two different equations for curvature, one involving the unit tangent vector T and the other involving the position vector R. The speaker is questioning the validity of the first equation and how it is derived. However, they believe that both equations are equivalent and can be derived from the basic definition of curvature as the angle turned over curve length traveled. They also suggest checking a website for further clarification.
  • #1
jaejoon89
195
0
My teacher wrote an alternative equation on the board for curvature, and I am wondering how it is true:

k = | dT/dt / |dR/dt| |

where T is the unit tangent vector.

I know k = |R' x R''| / |R'|^3 = |dT/ds|
but I am not sure about the formula in question. How is it true/derived?
 
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  • #2
i think these are equivalent, i think the basic definition of curvature is |dT|/ds,meaning the angle turned over curve length traveled, indeed you can find |dT| is angle turned if T is unit tangent vector,and ds=|dR| where R is the position vector, and all the mentioned formulas can be derived.
 
  • #3
Check out this website for clarification.

http://www.usd.edu/~jflores/MultiCalc02/WebBook/Chapter_14/Graphics/Chapter14_3/Html14_3/14.3%20Arc%20Length%20and%20Curvature.htm
 
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Related to Curvature in terms of the tangent vector

1. What is curvature in terms of the tangent vector?

Curvature in terms of the tangent vector refers to the rate of change of the direction of the tangent vector along a curve. It is a measure of how quickly the tangent vector is rotating as it moves along the curve.

2. How is the curvature in terms of the tangent vector calculated?

The curvature in terms of the tangent vector is typically calculated using the formula k=|dT/ds|, where k is the curvature, dT/ds is the rate of change of the tangent vector, and | | represents the magnitude. This formula can also be written as k=|dθ/ds|, where θ is the angle between the tangent vector and a fixed direction.

3. What is the relationship between curvature and the radius of curvature?

The radius of curvature is the radius of the circle that best approximates a curve at a particular point. The curvature is inversely proportional to the radius of curvature, meaning that as the curvature increases, the radius of curvature decreases. This relationship can be seen in the formula k=1/r, where r is the radius of curvature.

4. How does the tangent vector change as the curvature increases?

As the curvature increases, the tangent vector changes more rapidly, meaning that it rotates at a faster rate. This is because the tangent vector is always perpendicular to the curve, and as the curve becomes more curved, the direction of the tangent vector changes more rapidly.

5. Can the curvature in terms of the tangent vector be negative?

Yes, the curvature in terms of the tangent vector can be negative. This typically occurs when the curve is concave, meaning that it bends inward. In this case, the tangent vector rotates in the opposite direction as the curve, resulting in a negative curvature value.

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