1. The problem statement, all variables and given/known data I'm having trouble understanding the physics equations related to Steering Behaviors For Autonomous Characters (present in the book "Programming Game AI by example"). For those that don't know- Seek is a kind of behavior whereby an object with a given mass, current position & velocity attemps to seek to a target position. 2. Relevant equations In the book, Mat Buckland calculates Seek like so (in Pseudocode) def Seek() DesiredVelocity = Normalize(TargetPos - VehiclePos) * VehicleMaxSpeed SteeringForce = DesiredVelocity - VehicleVelocity return SteeringForce 3. The attempt at a solution Seek is stated, in the book- to return a steering force, which is "the force required, when added to the agents current velocity vector, gives the desired velocity. How does the subtraction of two velocity vectors suddenly become a force? My heads in a spin- any help is greatly appreciated!