### Problem 1.11

#### Task:

Two particles move in a uniform gravitational field with an acceleration \( g \). At the initial moment the particles were located at one point and moved with velocities \( v_1 = 3.0 \) m/s and \( v_2 = 4.0 \) m/s horizontally in opposite directions. Find the distance between the particles at the moment when their velocity vectors become mutually perpendicular.