### Problem 1.13

#### Task:

Point \( A \) moves uniformly with velocity \( v \) so that the vector \( \vec{v} \) is continually "aimed" at point \( B \) which in its turn moves rectilinearly and uniformly with velocity \( u < v \). At the initial moment of time \( \vec{v} \perp \vec{u} \) and the points are separated by a distance \( l \). How soon will the points converge?