Why can’t we convert cars to run on their own kenetic energy?


Why can’t we convert cars to run on their own kenetic energy?

In: Engineering

The kinetic energy of the car is energy converted by the engine from the fuel (diesel/petrol/electricity). It isn’t an inherent property of a car nor can it be created out of nothing.

Cars that are moving have kinetic energy BECAUSE of their engines.

Because that’s physically impossible.

The total loss of energy makes sure you always need an external source of power.

Friction (air resistance, ground resistance, moving parts in the engine…), heat… All take energy away.

Kinetic energy is energy from motion. So a car at rest has zero kinetic energy and will not be able to get moving.

Some cars (Teslas, Priuses, etc.) are able to recapture some kinetic energy with regenerative braking. When you brake in those cars, it recaptures some of the kinetic energy and charges the batteries, which can be used to accelerate the car. But you need a hybrid or electric car to do this, because you need batteries to accept this charge.

Energy is neither created nor destroyed but simply transformed.

This means that a stopped car can’t start moving without energy input to the system. This energy is stored chemically in gasoline, but I suppose you could also get a team of men to push the car utilizing energy stored in the human bodies.

Once the car is moving, forces like friction and air resistance are always working to slow the car down *by taking kinetic energy from the car*. You can’t add energy to the car by taking kinetic energy *from* the car. The energy needs to come from somewhere else.

Your question communicates a fundamental misunderstanding about energy and the impossibility of perpetual motion.