# Vectors -

1. Dec 22, 2007

### discombobulated

[SOLVED] vectors -

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

At time t = 0 two forces f1 = (i + j) and f2 = (2i - 2j) start acting on a point body of unit mass lying stationary at the point (1,2) of the x,y plane. Describe the trajectory r(t) of the plane.

2. Relevant equations

F = ma

a = d2x/dt2

3. The attempt at a solution

Total force, F = (i + j) + (2i - 2j)
F = (3i - j)

I know I need to integrate using the acceleration equation but I'm confused by the x,y plane, I thought it was meant to be in i,j plane? :S Could someone please explain?
Thanks!

2. Dec 22, 2007

### Hootenanny

Staff Emeritus
i and j are unit vectors in the direction of the positive x and positive y direction respectively, so you're still working in the x-y plane.

3. Dec 22, 2007

### discombobulated

thanks, so do i split it like this, d2x /dt2 = 3 and d2y /dt2 = -1 and then when I integrate to get x and y, put it back into i and j form?

4. Dec 22, 2007

### Hootenanny

Staff Emeritus
Sounds good to me