Relative velocity and closing speed

This article discusses the concept of closing speed, defined as the normal component of the relative velocity between two objects, often used in physics simulations and game engines. It explains how to compute the relative velocity vector, split it into normal and tangential components, and use vector projection to find the closing speed. The article provides mathematical formulas, clarifies sign conventions (positive for separating, negative for approaching), and includes worked examples to build intuition. It is relevant to developers working on physics engines, collision detection, or any simulation involving object interactions.