MathDB
Math with particles

Source: Kvant Magazine No. 4 2021 M2649

March 9, 2023
combinatoricscombinatorial geometryKvant

Problem Statement

Initially, the point-like particles A,BA, B and CC{} are located respectively at the points (0,0),(1,0)(0,0), (1,0) and (0,1)(0,1) in the coordinate plane. Every minute some two particles repel each other along the straight line connecting their current positions, moving the same (positive) distance.
[*]Can the particle AA{} be at the point (3,3)(3,3)? What about the point (2,3)(2,3)? [*]Can the particles BB{} and CC{} be at the same time at the points (0,100)(0,100) and (100,0)(100,0) respectively?
Proposed by K. Krivosheev