Finding the Resolved Part of a Vector in a Given Direction

[Gregg]

Homework Statement

Write down the resolved part of vector r in the direction of a, where $a=\left(<br /> \begin{array}{c}<br /> 0 \\<br /> 0 \\<br /> -1<br /> \end{array}<br /> \right)$

EDIT:
$r=\left(<br /> \begin{array}{c}<br /> 3 \\<br /> 4 \\<br /> 5<br /> \end{array}<br /> \right)$

The Attempt at a Solution

I don't know what this means, the resolved part of vector r.

 

[Mark44]

I don't either, but I suspect it has something to do with the component of r in the direction of a. See if your textbook defines the term "resolved part of a vector" somewhere.

Mathematics relies heavily on definitions. Whenever you have a problem that says "find the XYZ" and you don't know what XYZ is, look for its definition and go from there.

 

[Gregg]

The answer is just '-5'. The text doesn't define it anywhere its a really crap text. The questions are from past papers from different exam boards.

 

[Cyosis]

To add to what Mark said. If I don't know a definition and I am behind my pc, I use google. More often than not I will know the meaning of the definition in mere seconds.

I tried it for this problem as well and the first hit was:

http://thesaurus.maths.org/mmkb/entry.html?action=entryById&id=3779

Five seconds at most!

And yes the answer is -5.

I don't want to discourage you from asking questions of course, but being somewhat independent will save you a lot of time which you can spend on more important things!

 

[tiny-tim]

… I don't know what this means, the resolved part of vector r.

Yes, it's a bit old-fashioned now, but some people say "resolve all the forces in the x-direction" when they mean "find the components of all the forces in the x-direction" …

it's using one word instead of two or three.

 

[Gregg]

The resolved part of a in the direction of b is $\frac{a.b}{|b|}$

This in the formula book :)