2 The unit vectors \(\mathbf { i }\) and \(\mathbf { j }\) are directed due east and due north respectively.
Two runners, Albina and Brian, are running on level parkland with constant velocities of \(( 5 \mathbf { i } - \mathbf { j } ) \mathrm { m } \mathrm { s } ^ { - 1 }\) and \(( 3 \mathbf { i } + 4 \mathbf { j } ) \mathrm { m } \mathrm { s } ^ { - 1 }\) respectively. Initially, the position vectors of Albina and Brian are \(( - 60 \mathbf { i } + 160 \mathbf { j } ) \mathrm { m }\) and \(( 40 \mathbf { i } - 90 \mathbf { j } ) \mathrm { m }\) respectively, relative to a fixed origin in the parkland.
- Write down the velocity of Brian relative to Albina.
- Find the position vector of Brian relative to Albina \(t\) seconds after they leave their initial positions.
- Hence determine whether Albina and Brian will collide if they continue running with the same velocities.