Vector function, position and tangent vectors

In summary, the conversation discusses how to show that a curve lies on a sphere with center at the origin if the position vector is always perpendicular to the tangent vector. This is achieved by differentiating the dot product of the position vector and showing that it equals 0, indicating a constant magnitude and therefore a sphere with center at the origin.
  • #1
Maianbarian
3
0

Homework Statement


If a curve has the property that the position vector r(t) is always perpendicular to the tangent vector r'(t) show that the curve lies on a sphere with center at the origin


Homework Equations



The Attempt at a Solution



I have no idea how to even approach this problem, if somebody could give me a nudge in the right direction it would be much appreciated.
 
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  • #2
Differentiate r(t).r(t) (the dot product).
 
  • #3
Ah, I get it now.

We know that r(t).r(t)=|r(t)|^2. Differentiating the dot product we get:

d/dt [r(t).r(t)]= 2r'(t).r(t) = 0 (as r'(t) is orthogonal to r(t))

thus |r(t)|^2 is constant, and so |r(t)| is constant, which corresponds to a sphere with the centre at the origin.

Thanks Dick :)
 

1. What is a vector function?

A vector function is a mathematical function that maps a set of input values to a set of output values, where both the input and output are vectors. In other words, it is a function that takes in multiple variables and returns a vector as the output.

2. How is position related to vector function?

In the context of vector functions, position refers to the location of a point in space. Vector functions can be used to describe the position of a point in space by using vectors to represent the coordinates of the point.

3. What is a tangent vector?

A tangent vector is a vector that is tangent to a curve at a specific point. It represents the direction and rate of change of the curve at that point. Tangent vectors are often used in calculus to calculate the slope of a curve at a given point.

4. How do you find the tangent vector of a vector function?

The tangent vector of a vector function can be found by taking the derivative of the function with respect to the independent variable. This will give a new vector function that represents the rate of change of the original function at each point.

5. What is the significance of tangent vectors in physics?

In physics, tangent vectors are used to represent the velocity and acceleration of an object in motion. By using tangent vectors, we can analyze the direction and magnitude of an object's motion at a specific point in time. This is crucial in understanding the dynamics of physical systems.

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