# Homework Help: Finding the work done using force vectors in 3 dimensions

1. Mar 13, 2013

### dan38

1. The problem statement, all variables and given/known data
Find the work done by a force acting in the direction 2i - 5j + k in moving a particle from (3, 3, 1) to (1, 2, 4).

2. Relevant equations

3. The attempt at a solution
I just found the displacement vector (2,1,-3) and did the dot product with the force vector.
So my answer as an integer, was negative 4.
Does that sound correct?

2. Mar 13, 2013

### Curious3141

The question is somewhat imprecise; the force doesn't just act in that vector direction, it is given by that vector. Force has direction and magnitude - if they only meant that vector to represent the direction, they need to state the magnitude separately.

You got a negative answer because you took the wrong direction for the displacement vector. What is displacement? Is it final minus initial position or vice versa?

3. Mar 13, 2013

### dan38

oh yeah lol, its final minus initial
so my answer should be positive 4 right?

4. Mar 13, 2013

### Curious3141

Yes. Units would be nice, but if you weren't given any for the force and distance, what can you do?