At 12 p.m. a hiker X X\,X has position vector (−2i+3j)(-2\mathbf{i} + 3\mathbf{j})(−2i+3j) km relative to a fixed origin O O\,O and moves with constant velocity (4i−2j)(4\mathbf{i} - 2\mathbf{j})(4i−2j) km h−1\text{h}^{-1}h−1. Another hiker Y Y\,Y has position vector (6i−5j)(6\mathbf{i} - 5\mathbf{j})(6i−5j) km relative to a fixed origin O O\,O and moves with constant velocity (−4i+6j)(-4\mathbf{i} + 6\mathbf{j})(−4i+6j) km h−1\text{h}^{-1}h−1.
Find expressions for the position vectors of X X\,X and YYY, in terms of t t\,t hours after 12 p.m.
Show that if both hikers maintain their course and speed, they will collide and find the time and position vector at which this occurs.
At 12:30 p.m. hiker X X\,X changes course and now moves with velocity (10i+10j)(10\mathbf{i} + 10\mathbf{j})(10i+10j) km h−1\text{h}^{-1}h−1. Find the distance between the two hikers at the time when they would have collided.
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.