Finding Curvature of Vector Function

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In summary, the goal is to find the curvature of a curve using the arc length parameter. The Frenet-Serret formulae and chain rule can be used, without the need for integration. The choice of the lower limit of the integral in the arc length function is arbitrary, usually set to the starting point of the curve, but can be kept in the expression without affecting the solution.
  • #1
Bashyboy
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Homework Statement


Find the curvature K of the curve, where s is the arc length parameter:

[itex]\vec{r}(t) = \langle 2 \cos t , 2 \sin t, t \rangle[/itex]

Homework Equations



[itex]s(t) = \int_a ^t ||\vec{r}'(u)||du[/itex]

The Attempt at a Solution



I know I need to find the arc length function, in order to find the curvature function; however, I am unsure as to what I should choose a to be for the lower limit of the integral.
 
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  • #2
You need to use the Frenet-Serret formulae and the chain rule.

You should not need to perform any integrations.
 
Last edited:
  • #3
Bashyboy said:

Homework Statement


Find the curvature K of the curve, where s is the arc length parameter:

[itex]\vec{r}(t) = \langle 2 \cos t , 2 \sin t, t \rangle[/itex]




Homework Equations



[itex]s(t) = \int_a ^t ||\vec{r}'(u)||du[/itex]

The Attempt at a Solution



I know I need to find the arc length function, in order to find the curvature function; however, I am unsure as to what I should choose a to be for the lower limit of the integral.

Choose it so that s(0)=0.
 
  • #4
So, the choice is arbitrary? If so, why?
 
  • #5
Bashyboy said:
So, the choice is arbitrary? If so, why?

Why not? Just as you can start time at any instant, you can measure an arc length from any point on a line. Usually the arc length is connected to the trajectory of an object if time is involved, that is why I suggested s(0)=0. But you also can keep "a" in the expression s(t). Solve the problem and you will see that"a" cancels.

ehild
 

1. What is the definition of curvature in a vector function?

The curvature of a vector function is the measure of how much the direction of the function changes as we move along its curve. In other words, it is a measure of the rate of change of the tangent vector to the curve.

2. How do you find the curvature of a vector function?

To find the curvature of a vector function, we use the formula K = ||T'(t)|| / ||r'(t)||, where T'(t) is the derivative of the tangent vector and r'(t) is the derivative of the position vector. This gives us the magnitude of the curvature at a specific point on the curve.

3. What is the significance of finding the curvature of a vector function?

The curvature of a vector function is important in many scientific and mathematical applications. It helps us understand the shape, smoothness, and behavior of curves and surfaces in space. It is also used in fields like physics, engineering, and computer graphics to model and analyze the motion of objects.

4. Can the curvature of a vector function be negative?

Yes, the curvature of a vector function can be negative. This occurs when the curve is bending in the opposite direction of the tangent vector at a given point. In other words, the curve is curving inwards instead of outwards.

5. Are there any practical applications of finding the curvature of a vector function?

Yes, there are many practical applications of finding the curvature of a vector function. It is used in fields like robotics, computer-aided design, and computer vision to analyze and manipulate curves and surfaces. It is also used in medical imaging to study and diagnose the shape of organs and tissues in the human body.

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