I have two objects and I want to find when will they collide. Lets say first target has position p0, velocity v0 and the time it will arrive at desired position is t0. Similar for the second target it has position p1, velocity v1 and the time t1.

The general formula for speed with constant velocity is:

p = v*t + p0

So if we try to find their colliding position p0 and p1 should be equal at desired time so p0 = p1.

v1 * t1 + p1 = v2 * t2 + p2

t2 = v1 * t1 + p1 - p2 / v2

t2 is the time that will second object arrive at colliding position.

I wonder how we can calculate this ? On the right hand side of last equation we have vector division. So since t2 is a scalar on the right hand side there also must be a scalar. So I think we should take the magnitude of vectors on right side and divide them.

What to do in these situations when we have a division of two vectors ? Is this approach correct one ?

**Edited by ryt, 20 January 2014 - 01:42 PM.**