Simple Vector Problem


by Loppyfoot
Tags: simple, vector
Loppyfoot
Loppyfoot is offline
#1
Oct21-10, 06:38 PM
P: 187
1. The problem statement, all variables and given/known data

Find two vectors, v1, and v2, whose sum is <-4,1,1>, where v1 is parallel to <2,5,-4>, and where v2 is perpendicular to <2,5,-4>



2. Relevant equations

I am guessing I use the cross product for this equation, but I'm confused about how to start this problem.

3. The attempt at a solution

any hlep at all would be greatly appreciated!
Phys.Org News Partner Science news on Phys.org
SensaBubble: It's a bubble, but not as we know it (w/ video)
The hemihelix: Scientists discover a new shape using rubber bands (w/ video)
Microbes provide insights into evolution of human language
Mark44
Mark44 is online now
#2
Oct21-10, 06:49 PM
Mentor
P: 21,069
Quote Quote by Loppyfoot View Post
1. The problem statement, all variables and given/known data

Find two vectors, v1, and v2, whose sum is <-4,1,1>, where v1 is parallel to <2,5,-4>, and where v2 is perpendicular to <2,5,-4>



2. Relevant equations

I am guessing I use the cross product for this equation, but I'm confused about how to start this problem.
Don't use the cross product.

Write v1 and v2 using coordinates. You're given that they add to <-4, 1, 1>. You're also given that v1 is parallel to <2, 5, -4>, which means that v1 is some constant multiple of <2, 5, -4>. You're also given that v2 is perpendicular to <2, 5, -4>. Two vectors being perpendicular should suggest a particular operation.
Loppyfoot
Loppyfoot is offline
#3
Oct21-10, 06:55 PM
P: 187
So, first I realized that v1= K<2,5,-4>

Then I figured that since v1+v2=sum, ;
then:

<4,1,1> - K<2,5,-4> = v2

Now, what process would I use to find K?

Mark44
Mark44 is online now
#4
Oct21-10, 07:26 PM
Mentor
P: 21,069

Simple Vector Problem


Quote Quote by Loppyfoot View Post
So, first I realized that v1= K<2,5,-4>
Then what are the coordinates of v1?

Quote Quote by Loppyfoot View Post

Then I figured that since v1+v2=sum, ;
then:

<4,1,1> - K<2,5,-4> = v2

Now, what process would I use to find K?
How about finding coordinates for v2 first?

Also what can you do with the given information that v2 is perpendicular to <2, 5, -4>?


Register to reply

Related Discussions
A simple (?) vector problem Calculus & Beyond Homework 6
Really simple Vector problem. Calculus & Beyond Homework 3
Simple Vector Problem Calculus & Beyond Homework 4
Simple Vector Problem. Help please! Precalculus Mathematics Homework 1
A simple vector problem Introductory Physics Homework 1