Vector Manipulation (Orthogonal and Parallel Vectors)

In summary, to determine vectors v and w such that a=v+w and v is parallel to b while w is orthogonal to b, we can use the fact that the dot product of two orthogonal vectors is zero and the cross product of two parallel vectors is zero. This means that v must be a scalar multiple of b, and w can be found by subtracting v from a. By setting the dot product of w and b to zero, we can solve for t and find the values of v and w.
  • #1
adam199
17
0
Consider the vectors a=<2,4,-3> and b=<4,-5,6>. Determine vectors v and w such that a=v+w and v is parallel to b while w is orthogonal to b.The dot product of two orthogonal vectors is zero and the cross product of two parallel vectors is zero. A parallel vector is a multiple of the chosen vector.I tried using multiples of b for v and then seeing if random vectors orthogonal to b can be added to v to give a. I'm lost here.
 
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  • #2
adam199 said:
Consider the vectors a=<2,4,-3> and b=<4,-5,6>. Determine vectors v and w such that a=v+w and v is parallel to b while w is orthogonal to b.The dot product of two orthogonal vectors is zero and the cross product of two parallel vectors is zero. A parallel vector is a multiple of the chosen vector.I tried using multiples of b for v and then seeing if random vectors orthogonal to b can be added to v to give a. I'm lost here.

Instead of expressing parallel as a cross product, if v is parallel to b then v must be a scalar multiple of b. So v=tb for some t. That means w=a-v=a-tb. Now w.b must be 0. Try to solve for t.
 
  • #3
Dick said:
Instead of expressing parallel as a cross product, if v is parallel to b then v must be a scalar multiple of b. So v=tb for some t. That means w=a-v=a-tb. Now w.b must be 0. Try to solve for t.

I tried using w=a-tb. I dotted both sides by b, and got 0=(a-tb).b, where t is the only unknown, but I got stuck again. I'm not quite sure how to solve for t at that point.
 
  • #4
adam199 said:
I tried using w=a-tb. I dotted both sides by b, and got 0=(a-tb).b, where t is the only unknown, but I got stuck again. I'm not quite sure how to solve for t at that point.

Distribute the dot product. (a-tb).b=a.b-t(b.b)=0. Now try it.
 
  • #5
Dick said:
Distribute the dot product. (a-tb).b=a.b-t(b.b)=0. Now try it.

thanks
 

Related to Vector Manipulation (Orthogonal and Parallel Vectors)

1. What is the difference between orthogonal and parallel vectors?

Orthogonal vectors are two vectors that are perpendicular to each other, meaning they form a 90 degree angle. Parallel vectors, on the other hand, have the same direction and magnitude, but may have different starting points.

2. How do you determine if two vectors are orthogonal?

To determine if two vectors are orthogonal, you can use the dot product. If the dot product of the two vectors is zero, then they are orthogonal. This is because the dot product is equal to the product of the magnitudes of the two vectors multiplied by the cosine of the angle between them, and if the angle is 90 degrees, the cosine will be zero.

3. Can you have more than two orthogonal vectors in a set?

Yes, you can have any number of orthogonal vectors in a set. As long as each vector is perpendicular to all other vectors in the set, they are considered orthogonal.

4. How are orthogonal vectors used in real life?

Orthogonal vectors are used in many areas of science and engineering, such as physics, computer graphics, and navigation. In physics, they are used to represent forces and motion in different directions. In computer graphics, they are used to create 3D images and animations. In navigation, they are used to determine the direction and distance of objects.

5. How do you find the components of a vector that are parallel and orthogonal to another vector?

To find the components of a vector that are parallel and orthogonal to another vector, you can use the projection formula. The parallel component is equal to the dot product of the two vectors divided by the magnitude of the second vector, multiplied by the second vector. The orthogonal component is equal to the original vector minus the parallel component.

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