Before we can delve into the energy-based model, we must define a couple new quantities. Two of them are work and kinetic energy. We all use the term work in our everyday language, so I'm sure you have a sense of what it means. Be careful, though: In physics, work has a very precise definition. Work is equal to force times displacement.
W = FΔx
Δx = displacement
F = force in the direction of displacement.
If work is defined as force times displacement, this means that the object must move for work to be done. This might contradict your current perception of work. For example, if you push against a brick wall until you work up a sweat, you might think you've worked really hard. However, a physicist will ...