Two particles `A` and `B` are initially `40 m`apart, `A` is behind `B`. Particle `A` is moving with

Two particles `A` and `B` are initially `40 m`apart, `A` is behind `B`. Particle `A` is moving with uniform velocity of `10 m s^(-1)` towared `B`. Particle `B` starts moving away from `A` with constant acceleration of `2 m s^(-1)`. The time which there is a minimum distance between the two is .