Two drones, Phoenix and Icarus, are performing a synchronized survey of a forest fire. Both drones fly in the same direction along straight, parallel paths at a constant altitude.
Phoenix maintains a constant velocity of (3i+4j) m s−1(3\mathbf{i} + 4\mathbf{j})\text{ m s}^{-1}(3i+4j) m s−1.
At time t=0t = 0t=0 seconds, Icarus is at the position (7i−24j) metres(7\mathbf{i} - 24\mathbf{j})\text{ metres}(7i−24j) metres and is moving with a constant speed of 15 m s−115\text{ m s}^{-1}15 m s−1.
(i) Explain why Icarus's velocity must be of the form k(3i+4j) m s−1k(3\mathbf{i} + 4\mathbf{j})\text{ m s}^{-1}k(3i+4j) m s−1, where kkk is a constant.
(ii) Show that k=3k = 3k=3.
Determine the position vector of Icarus when t=2t = 2t=2.
At both t=0t = 0t=0 and t=2t = 2t=2, the distance between Phoenix and Icarus is 26 metres26\text{ metres}26 metres.
Calculate the shortest distance between their two parallel lines of flight.
Fully justify your answer.
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.