# Thread: Vectors

1. ## Vectors

O(0,0,0), A(4,0,0), B(1,3,0) and C(1,1,2) are vertices of a parallelepiped having OA,OB and OC as concurrent edges. Forces of magnitudes 7, 2 and 4 act on a particle at O in the directions pointing towards A,B and C respectively. Determine the resultant force on the particle. What is the component of the resultant, along the diagonal of the parallelepiped.

2. ## Re: Vectors

What exactly is your difficulty? It is difficult to know what suggestions would help if you don't show any work of your own.

3. ## Re: Vectors

Well I know how to calculate the resultant by taking the unit vectors along the directions on which the forces are acting , multiplying them by the magnitude for the forces so that I get the 3 forces as 3 vectors and the resultant is just the addition of the 3 vectors.
What I'm having the difficulty is getting the component of the resultant along the diagonal of the parallelepiped.
I think I can get the component by taking the dot product of the resultant with the unit vector along the diagonal of the parallelpiped but I just cannot find a way to get the unit vector. Or is there any other easy way of doing it?