In Chapter 1, we learned how to find the position, velocity, and acceleration of a particle – its kinematic description – without worrying about the forces causing its motion. While this constitutes an important first step towards learning dynamics, kinematics does not lend itself naturally to obtaining the equations governing the motion of the particle. Such equations are what we are after in this book because, through their solution, we can describe and predict motion of particles. This chapter outlines the most common approach – the vectorial approach – through which the equations governing the motion of particles are derived. To this end, we introduce Newton’s second law of dynamics and demonstrate how it can be used to relate the forces acting on a particle to its ensuing motion. Examples involving planar and non-planar motion are discussed.