# Finding velocity along a vector, given velocity in xyz

1. Homework Statement
I am attempting to program a simulation of a ball hitting a wall (breakout, basically), and am having problem with the maths elements. I have the angle at which the object strikes the wall, and currently I am working on the seperation velocity. However, I don't know how to find this.

I have the velocity of the ball in the XYZ, but don't know how to combine these into a velocity along a vector. Also how would i then take the velocity after impact and seperate this back into the XYZ components? I think it would involve scaling the values but I'm not certain on this.

2. Homework Equations
v^2 = u^2(cos^2 a + e^2 * sin^2 a)
(I have a and e, and need u to solve the equation)

3. The Attempt at a Solution
Well...everything up till here. Using a plane->vector intersection formula (n.b = |n||b|sinA ...where n is the plane normal, b is the vector and A is the angle) to find the angle the vector makes with the plane.