Homework Help: 3d-Vector question

1. Apr 21, 2013

lionely

1. The problem statement, all variables and given/known data

I'm confused ,

here's ... my attempt..

all I know so far is the

the k component would be 5...
I have no idea what to do with the i and j

Last edited: Apr 22, 2013
2. Apr 22, 2013

tiny-tim

hi lionely!
drop perpendiculars DP and EQ onto the base …

where are P and Q in relation to ABCD ?

3. Apr 22, 2013

SteamKing

Staff Emeritus
Hint: Assume DE is located such that its midpoint is positioned directly over the intersection of the base diagonals OB and AC.

4. Apr 22, 2013

lionely

Hmm is DE is assumed to be at the mid point then.. for the j component that would be 4j

but the i? ... umm is it like the base below DE is 8 because DE is 6cm and OA is 14? so 14-6?

5. Apr 22, 2013

lionely

when I dropped the perpendiculars they ended up being at the midpoints of the widths of the base

6. Apr 22, 2013

Staff: Mentor

You had your answer in this post, but didn't realize it. 14 - 6 = 8, and this difference is split evenly between between the two sides. So the i component is 4.

7. Apr 23, 2013

tiny-tim

hi lionely!

(just got up :zzz:)
(we'll call them P and Q)

ok … so the next line in your proof would be to say what the distance PQ is

and then you can compare that with the length of the base