Why is the Vector (Cross) Product pxq Perpendicular to a Plane?

In summary, the conversation discusses the relationship between two vectors p and q, and the vector (cross) product pxq. It is noted that the cross product is perpendicular to the plane containing p and q, but there may be different ways to explain this concept. Some resources, such as online introductions to multivariable calculus and demonstrations by Greg Egan, relate the algebraic expression for the components of a cross product to the property of perpendicularity.
  • #1
matqkks
285
5
Given two vectors p and q, why is the vector (cross) product pxq perpendicular to the plane containing these vectors?
Is there a geometric or physical way of explaining why?
Are there any real life examples we can draw from?
 
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  • #2
Well, what is your definition of cross product? Sometimes this (perpendicularity) is part of the definition.
 
  • #3
Two links posted recently in these forums are online introductions to multivariable calculus which each contain a chapter relating the algebraic expression for the components of a cross product to the property of being perpendicular to its factors:

http://synechism.org/drupal/cfsv/
http://www.owlnet.rice.edu/~fjones/

Greg Egan used to have a nice demonstration of the correspondence between geometric and componentwise definitions of the dot product (which is taken as the starting point by the links above), but I can't seem to find it now. Never mind, Google knows lots more. You can shop around for the one that makes most sense to you.
 

1. Why is the vector (cross) product perpendicular to a plane?

The vector (cross) product, also known as the cross product, is a mathematical operation that takes two vectors as input and produces a third vector that is perpendicular to both of the original vectors. This means that the resulting vector is also perpendicular to the plane that contains the two input vectors. This property of the cross product is a result of the mathematical definition of the operation and can be proven using vector algebra.

2. How is the direction of the cross product determined?

The direction of the cross product is determined by the right-hand rule, which states that if the fingers of your right hand are curled in the direction of the first vector and then rotated towards the second vector, the direction of the resulting vector will be perpendicular to the plane formed by the two input vectors. This rule is a convention that is used to consistently determine the direction of the cross product.

3. Can the cross product be used in 2-dimensional space?

No, the cross product is only defined for vectors in 3-dimensional space. This is because the cross product requires the existence of a third dimension in order to produce a vector that is perpendicular to the plane formed by the two input vectors. In 2-dimensional space, there is no third dimension for the resulting vector to be perpendicular to.

4. What are the applications of the cross product?

The cross product has many applications in physics, engineering, and computer graphics. Some examples include calculating the torque of a force, determining the direction of magnetic fields, and creating 3D graphics in computer programs. It is also useful in solving problems involving 3-dimensional motion and rotation.

5. How is the cross product related to the dot product?

The cross product and dot product are both mathematical operations that involve vectors. While the cross product produces a vector as a result, the dot product produces a scalar. The cross product is used to determine the perpendicular component of two vectors, while the dot product is used to determine the parallel component. Additionally, the cross product is only defined for 3-dimensional vectors, while the dot product can be used for vectors in any dimension.

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