# Motion and Kinetic Energy Wikipedia says “In physics, the kinetic energy of an object is the energy that it possesses due to its motion. It is defined as the work needed to accelerate a body of a given mass from rest to its stated velocity. Having gained this energy during its acceleration, the body maintains this kinetic energy unless its speed changes”

The work-energy principle has an increase in the kinetic energy of a body equal to the work
done on the body by the force acting on it.
E = 1/2 mv2 is how we calculate kinetic energy. The work done by a steady force we calculate by multiplying it by the distance over which it is active.

Work done in accelerating a body from rest to speed v is the same as that to decelerate the same body from speed v to rest and I think that is why history led to kinetic energy as a motion energy store. This concept may work in our doing of quantitative calculations and in our treatment of energy as a scalar but it detracts from our understanding of what energy is. No wonder many scientists see kinetic energy as a mathematical construct but, by regarding it as as carried by a body in motion, that is precisely what we have make it into.

Does it make sense that you should see someone running the hundred metres as having gained in kinetic energy. It immediately puts this science view of albeit a named energy at odds with the general thinking about energy which would say it is something you lose when you are running. But then if you are running with that someone and they have no speed relative to you that measured energy is no longer there. Does it make sense that a 30 mph car approaching a 90 mph train has a kinetic energy store about 15 times greater when viewed from the train environment than when viewed by an earth observer?

Drop the concept of a motion energy store and regard kinetic energy as that involved in a motion change of v from a state of rest or uniform motion to another state of rest or uniform motion and that change v will be the same no matter what the speed of the observer. So if kinetic energies are energies associated with motion change why do bodies engage in motion? The answer might be in response to a force but then what is a force and why does the body move in response to it?

Regard a photon as a pulse of numerous living, light speed energies interacting so as to maintain the photon’s stable energy state. Consider it as engaging with a much bigger atomic particle, also of stable energy content and think of that particle as being part of a structure of many particles that have come together in interactions designed to better secure their energy stability and their energy desires.

If such engaging photons have energy that the particle structure wants, it will absorb and accommodate such energy. But, if the engaging photons have energies much in excess of the structure’s particle desires its particles will oppose such energies and thereby move away from them. In this scenario kinetic energy is the photon energies providing the interaction that we measure as a force and which moves the object some distance away from the unwanted energy allowing its return to its former energy stability.

Kinetic energy, far from being a motion energy store, is unwanted motion changing energy.