In this question the unit vectors i\mathbf{i}i and j\mathbf{j}j are due east and due north respectively, and all distances are in kilometres.
At noon, ship A A\,A is at the point (4i+6j)(4\mathbf{i} + 6\mathbf{j})(4i+6j) relative to a port OOO, and moves with constant velocity (3i−2j)(3\mathbf{i} - 2\mathbf{j})(3i−2j) km h−1^{-1}−1.
At the same time, ship B B\,B is at the point (−2i−4j)(-2\mathbf{i} - 4\mathbf{j})(−2i−4j) relative to OOO, and moves with constant velocity (6i+3j)(6\mathbf{i} + 3\mathbf{j})(6i+3j) km h−1^{-1}−1.
Write down, in terms of ttt, the position vector of each ship t t\,t hours after noon.
Show that the two ships collide, and state the time at which this happens.
197 exam-style questions on OCR A Level Maths 1.10 Vectors, covering 1.10.1 Vectors in two dimensions, 1.10.2 Vectors in three dimensions (A-level only), 1.10.3 Magnitude and direction of vectors, 1.10.4 Basic operations on vectors, 1.10.5 Position vectors, 1.10.6 Distance between points, 1.10.7 Problem solving using vectors, 1.10.8 Vectors in kinematics, and 1.10 Vectors. Each one has a worked solution and a mark scheme showing where the marks go.