Most of us know that when we pedal a bicycle and move the handlebars, it moves from its present location to wherever we take it. We understand that by exerting a little effort on a gas pedal and moving the steering wheel, the car moves where we need it to go. How do we apply this understanding to the navigation of a hot air balloon or the movements of simple machines? It all has to do with forces.

What is force? Force is energy applied to an object in a specific direction. Forces help planes fly, cars move, and towers stand. There are forces everywhere. Forces act upon everything around us, and to understand motion, you must first understand the forces that make motion possible.

On Earth, one force is always present — the force of gravity.