Vector Cross Product Homework: Solving AxB with B values of 8i+16j and -8i-16j

In summary, the question asks to evaluate AxB with different values of B. The solution can be found without computation as long as the vectors have the same or opposite direction, as their cross product will result in 0. This is because the vectors are parallel or colinear, and are scalar multiples of the same unit vector.
  • #1
noeinstein
14
0

Homework Statement



Given that A = 2i + 4j, evaluate each of the following. (Hint: This question can be answered without computation.)

(a) What is AxB when B = 8i + 16j?

(b) What is AxB when B = -8i - 16j?

Homework Equations



AxB=(Axi + Ayj) x (Bxi +Byj)
=(AxBx)(i x i) + (AxBy)(i x j) + (AyBx)(j x i) + (AyBy)(j x j)
AxB=(AxBy - AyBx)k

The Attempt at a Solution



AxB= (2 x 16)k - (4 x 8)k= 0k
 
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  • #2
Indeed.

Can you see the relation between A and B that makes the zero result trivial, i.e you can solve it "without" computation?
 
  • #3
They have the same/opposite direction?
 
  • #4
Geeze no kidding! dahh. Thanks
 
  • #5
noeinstein said:
They have the same/opposite direction?

Indeed.
The vectors involved are parallell. Therefore, their cross product must be 0.
 
  • #6
Try parallel or colinear. They are scalar multiples of the same unit vector.
 

Related to Vector Cross Product Homework: Solving AxB with B values of 8i+16j and -8i-16j

What is the definition of vector cross product?

The vector cross product, also known as the vector or cross product, is a mathematical operation that takes two vectors as input and produces a third vector that is perpendicular to both of the input vectors.

What is the formula for calculating the vector cross product?

The formula for calculating the vector cross product is:

a x b = |a||b| sin θ n

where a and b are the two input vectors, |a| and |b| are their magnitudes, θ is the angle between them, and n is a unit vector perpendicular to both a and b.

What are the properties of vector cross product?

The vector cross product has the following properties:

- It is not commutative: a x b ≠ b x a
- It is distributive: a x (b + c) = a x b + a x c
- It follows the right-hand rule: the direction of the resulting vector is perpendicular to both a and b, and is determined by curling the fingers of your right hand from a to b
- The magnitude of the resulting vector is equal to |a||b| sin θ, where θ is the angle between a and b.

What are some real-life applications of vector cross product?

The vector cross product has many real-life applications, including:

- Calculating the torque on a rotating object
- Finding the direction of magnetic fields
- Determining the angular momentum of a spinning object
- Solving problems in fluid mechanics
- Creating 3D graphics in computer programming

How is the vector cross product related to the dot product?

The vector cross product and the dot product are two different mathematical operations involving vectors. While the vector cross product produces a third vector, the dot product produces a scalar (a number). They are related in the sense that the dot product of two perpendicular vectors is equal to 0, and the cross product of two parallel vectors is also equal to 0.

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