# Parallel and Perpendicular Vectors

• Sep 1st 2009, 02:24 PM
Linnus
Parallel and Perpendicular Vectors
Given vector v= 3i + 4j and vector F=4i+j

find the component of vector F parallel to vector v
find the component of vector F perpendicular to vector v

I found the unit vector of v...but I'm not sure what I'm suppose to do with it. My textbook says (F dot v)v provided ll u ll=1

Thanks!
• Sep 1st 2009, 04:54 PM
HallsofIvy
Quote:

Originally Posted by Linnus
Given vector v= 3i + 4j and vector F=4i+j

find the component of vector F parallel to vector v
find the component of vector F perpendicular to vector v

I found the unit vector of v...but I'm not sure what I'm suppose to do with it. My textbook says (F dot v)v provided ll u ll=1

Thanks!

You mean "provided ||v||= 1". Since you have found unit vector u such that u is in the same direction as v (I assume that is what you mean by "the unit vector of v"), go ahead and apply that formula to F and u. What is $F\cdot u$? Then multiply the vector u by that number.
• Sep 2nd 2009, 04:49 PM
Linnus
$F \cdot v$ would be 12i+4j, right? Then do I multiply that by the unit vector of v? which would be 3/5i+4/5j? I'm not quite sure how you would multiply the unit vector with $F \cdot v$

Thanks again!