What is the Direction of A X B Using the Right Hand Rule?

In summary, for the given cases, the direction of A X B can be determined using the right hand rule. A points east and B points south results in a vector pointing into the page. A points east and B points straight down also results in a vector pointing into the page. A points straight up and B points north results in a vector pointing into the page. A points straight up and B points straight down results in a vector pointing into the page. It is important to differentiate between south and straight down, as they are not in the same direction. The right hand rule can be visualized by imagining a jar with a right-hand screw lid and observing the direction of the cap movement when rotating one vector into the other.
  • #1
belvol16
9
0

Homework Statement


The direction of vectors A and B are given below for several cases. For each case, state the direction of A X B.
a) A points east, B points south.
b) A points east, B points straight down.
c) A points straight up, B points north.
d) A points straight up, B points straight down.

Homework Equations


Using the right hand rule.

The Attempt at a Solution


So, I've tried to use the right hand rule but I am not sure if I am using it properly. (I haven't taken multivariable calculus yet so I struggle with dot products and vector cross products). I used my pointer finger as my x-axis, middle finger as my y-axis, and thumb as my z-axis.
a) I found that the vector points into the page. I put my index finger towards the east and middle finger south and found that my thumb pointed into my page.
b) I guess I'm not sure if pointing straight down is different than pointing south. If pointing straight down is the same as south, then b) points into the page as well.
c) I'm a little bit confused. I took both my index finger and middle finger and pointed them up and found the resultant vector points into the page.
d) I stuck my pointer finger up and middle finger down and found that the resultant vector points into the page.
I guess I don't quite understand how all of these vectors point into the page or if I'm doing something wrong. I've watched a few other tutorials using a method where you curl your fingers, but I didn't quite understand how those worked.
Any help is greatly appreciated.
 
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  • #2
I think you should view it as a map laying on a table. So there are three orthogonal axes - (1) east - west, (2) north-south, (3) up-down. So down is not in the same direction as south. So I would use up-down instead of into and out of the page, because it is less confusing.
 
  • #3
I agree with phyzguy. Imagine that you are standing outside on level ground. N, S, E, and W would be directions parallel to the ground. "Straight up" would be vertically upward, perpendicular to the ground. "Straight down" would be vertically downward, perpendicular to the ground.
 
  • #4
I never used my fingers on the right hand rule for a vector cross-product. Instead, I envision a jar with a lid with a right-hand screw (right-hand is standard on all jars), and which way the cap moves (up or down) when you rotate it=e.g. rotating one vector into the other.
 

1. What is a vector cross product?

A vector cross product is a mathematical operation that takes two vectors and produces a third vector that is perpendicular to both of the original vectors. It is also known as a vector product or a cross multiplication.

2. How is a vector cross product calculated?

The vector cross product is calculated using the formula a x b = |a||b|sinθn, where a and b are the two vectors, θ is the angle between them, and n is the unit vector perpendicular to both a and b. The result is a vector in the direction of n with a magnitude equal to |a||b|sinθ.

3. What is the significance of the magnitude and direction of a vector cross product?

The magnitude of a vector cross product represents the area of the parallelogram formed by the two original vectors. The direction of the vector is perpendicular to both a and b, and follows the right-hand rule, where the thumb points in the direction of a and the index finger points in the direction of b, then the middle finger points in the direction of the resulting vector.

4. In what situations is a vector cross product commonly used?

Vector cross products are commonly used in physics and engineering, particularly in the fields of mechanics, electromagnetism, and fluid dynamics. They are also used in 3D computer graphics and computer vision algorithms.

5. What is the difference between a vector cross product and a scalar cross product?

A vector cross product produces a vector as its result, while a scalar cross product produces a scalar (a number) as its result. The scalar cross product is calculated using the formula a x b = |a||b|sinθ, without the unit vector n. The scalar cross product represents the magnitude of the vector cross product.

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