The task involves sending a helicopter from a task force to destroy an enemy submarine, yet the tools employed are no more warlike than a pencil, paper and an on-screen calculator. Kinematics is the latest module in the Royal Navy’s A-level maths site, and it makes a challenging addition to previous problems in projectile motion, calculus and probability. Students can solve the real-life predicament in class or at home. It should take them a couple of hours, because the first weapon fails, the submarine dives, and the setting of a depth charge necessitates working out a vector in three dimensions. The Royal Navy maths site is at: www.rn-maths.co.uk