|
|
As the particles move with constant velocities their position vectors are r1(t) = r1 + v1t r2(t) = r2 + v2t At the instant of collision, say at t = T, r1(T) = r2(T) r1 + v1T = r2 + v2T r1 - r2 = (v2 - v1)T Hence r1 - r2 and (v2 - v1) are parallel vectors. As they are parallel vectors, unit vectors along them must be same. Hence, r1 - r2/|r1 - r2| = (v2 - v1)/|(v2 - v1)|
|