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.
168 exam-style questions on AQA A Level Maths 1.13 J: Vectors, covering 1.13.1 Vectors in two and three dimensions, 1.13.2 Magnitude and direction of a vector, 1.13.3 Vector arithmetic, 1.13.4 Position vectors, and 1.13.5 Vectors to solve problems. Each one has a worked solution and a mark scheme showing where the marks go.