### Problem 1.16

#### Task:

Two particles, \( 1 \) and \( 2 \), move with constant velocities \( v_1 \) and \( v_2 \) along two mutually perpendicular straight lines toward the intersection point \( O \). At the moment \( t = 0 \) the particles were located at the distances \( l_1 \) and \( l_2 \) from the point \( O \). How soon will the distance between the particles become the smallest? What is it equal to?