Dot products in spherical or cylindrical coordinates

In summary, the conversation is about how to calculate the dot product of two vectors in spherical coordinates. The vectors in question have only an r component and it is discussed whether or not you can simply multiply the r components. The conversation then moves on to discuss how to determine if the vectors are parallel and if the dot product of parallel vectors is just the product of their magnitudes. It is suggested to check the definition of dot product for clarification.
  • #1
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Homework Statement


I'm doing a question that requires me to take the dot product of 2 vectors in spherical coordinates. Both vectors have only an r component, can I just multiply the r components?

Homework Equations

The Attempt at a Solution

 
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  • #2
Sketch the vectors and see.
Do they both point in the same direction?
What does a dot product do?
 
  • #3
Sorry probably should have been more specific. The 2 vectors are actually an electric field and electric displacement. Both have only an r component. Based on what you have said I assume that if they are parallel you can just multiply the components together. Since both the electric field and displacement have only an r component I assume that they are parrallel at all points and thus the dot product is equal to the product of the r components. Does this make sense?
 
  • #4
You can check by sketching the vectors and looking... are they parallel? You should be able to see.
The next question is if the dot product of parallel vectors is just the product of their magnitudes... you should not have to assume anything here: check the definition of dot product and you will know.
 

Related to Dot products in spherical or cylindrical coordinates

What is a dot product?

A dot product, also known as a scalar product, is a mathematical operation that takes two vectors and returns a single number. It is calculated by multiplying the corresponding components of the two vectors and then summing the results.

How is a dot product calculated in spherical coordinates?

In spherical coordinates, the dot product is calculated by taking the cosine of the angle between the two vectors and multiplying it by the magnitude of the first vector and the magnitude of the projection of the second vector onto the plane perpendicular to the first vector.

Why is the dot product useful in physics and engineering?

The dot product is useful in physics and engineering because it can be used to determine the angle between two vectors, the projection of one vector onto another, and the work done by a force along a given direction. It also has applications in areas such as mechanics, electromagnetism, and computer graphics.

How is a dot product calculated in cylindrical coordinates?

In cylindrical coordinates, the dot product is calculated by taking the cosine of the angle between the two vectors and multiplying it by the magnitude of the first vector and the magnitude of the component of the second vector in the direction of the first vector.

What are some real-world examples of using dot products in spherical or cylindrical coordinates?

One example of using dot products in spherical coordinates is in calculating the gravitational potential energy between two objects, such as planets. In cylindrical coordinates, dot products are used in calculating the moment of inertia of a rotating object and in determining the torque exerted by a force on a rotating object.

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