 To state this formally, in general an equation of motion is a function of the position of the object, its velocity (the first time derivative of , ), and its acceleration (the second derivative of , ), and time .Euclidean vectors in 3D are denoted throughout in bold.This is equivalent to saying an equation of motion in is a second-order ordinary differential equation (ODE) in ,

where is time, and each overdot denotes one time derivative.