As the natural resources of our planet have been depleted during the past century of industrialization, scientists have increasingly been searching for alternative methods to power vehichles, especially other than power by burning fossil fuels. Even after over 100 years of refinement, the modern automobile utilizes only about 15% of the energy avaliable in one gallon of gasoline. Most of the energy is wasted, lost in the form of heat from the exhaust, cooling, and lubrication systems, and, most importantly, in the braking system. New hybrid and electric cars are able to recapture this wasted energy and manipulate it into usable energy to power the vehicle. One of the main ways these amazing vehichles recapture the lost energy is through the process of regenerative braking, since braking is the main source of friction (and thus heat/energy loss) in the vehicle. One proposed hybrid car, FutureCar, will be able to recapture 40% of the energy typically "thrown away" during braking. The regenerative braking process that makes this and other similar vehiles possible is based mainly on the conservation of energy, a simple concept studied even in our entry-level physics class. Although other highly complicated electrical and computerized programs are used in these new cars, as described in the more detailed sections to follow, the basic laws of Conservation of Kinetic Energy and Conservation of Momentum are mostly responsible for making these new cars possible.

All moving objects possess kinetic energy, as well as momentum. Since a typical car, and even the smaller hybrid and electric cars of concern, has a high mass, its momentum is significant. Normal braking depends on friction between the brake pads and the tires to stop the car. Friction produces heat, and the friction needed to not only brake the momentum of a moving car but to bring it to a stop is great, producing a large amount of heat in the process. Normal cars simply allow this heat energy to to escape into the surroundings, but hybrid and electric cars that utilize regenerative braking convert this lost kinetic energy into elastic potential energy and electricity that can then be redistributed and used to power the car. This possiblity of this process should not be suprising to anyone familiar with basic physics, since the laws of physics simply state that the initial and final kinetic energy and momentum of a closed system always remains constant; energy cannot be gained or lost in the universe. Thus, in the small "universe" of a car engine, the avaliable energy can, and should, be utilized much more efficiently than it is presently in the millions of gasoline-powered cars. The motors of these cars also use high-torque springs to store the saved energy, since motor power is proportional to torque and speed. Thus, the cars are able to provide about the same amount of power and acceleration as the cars we drive now.