Two particles, 1 and 2, move with constant velocities `v_1` and `v_2`. At the initial moment their radius vectors are equal to `r_1` and `r_2`. How must these four vectors be interrelated for the particles to collide?

Options

A. `(vecr_(1)-vecr_(2))/(|vecr_(1)-vecr_(2)|)=(vecv_(1)-vecv_(2))/(|vecr_(1)-vecv_(2)|`
B. `(vecr_(1)-vecr_(2))/(|vecr_(1)-vecr_(2)|)=(vecv_(2)-vecv_(1))/(|vecr_(2)-vecv_(1)|`
C. `(vecr_(1)-vecr_(2))/(|vecr_(2)-vecr_(1)|)=(vecv_(2)-vecv_(1))/(|vecr_(1)-vecv_(2)|`
D. None of these

Answer

B