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 says an increase in the kinetic energy of a body equals 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.
The work done and energy involved in accelerating a body from rest to speed v is the same as that to decelerate the same body from speed v to rest but does it make sense that such accelerating and decelerating energies are carried on board with the object and remain with the as long as the object remains at its same gained steady speed.
The previous blog on the history of kinetic energy explained how kinetic energy became an on-board motion related energy store. This concept may work in our doing of quantitative calculations and in our treatment of energy as a scalar but the picture it creates seriously diminishes our understanding of what energy is. It is undoubtedly why many scientists see kinetic energy as a mathematical construct. By regarding it as as carried by a body in motion, that is precisely what we have made it into.
Does someone running the hundred metres gain and then give up an energy store. 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.
There is no external gravity force. There is a desire by the particles of an object for and to process earth energies. It is why the gravity acceleration g is independent of mass and the supposed gravity force is related to mass.
If we subject an earth bound body to unwanted k.e. it will accelerate away to and, so as to return to its former energy stability, shed itself of any energy it has gained If say the body leaves the earth at speed v in a upward direction its particle desires for earth energies will slow it so that it will be at omentary rest at height h.
The same body approaching the earth will, at speed v close to the earth, start to get energies in excess of its desires. They are unwanted kinetic energies that decelerate it and eventually locate it in a more stable energy exchanging location very close to but at a distance from earth particles. The vibrating particles of an object on the earth are showing us their desire for earth energies as opposed by their kinetic energy interactions intent on avoiding desire excesses.
Kinetic energy is not an onboard motion energy store and the height related so called gravitational potential energy store is not a special store. It is a desire that all structural particles above and on the earth have for the photon energies emitted by the earth.
The tale that says the onboard kinetic energy becomes potential energy in a rising body situation and potential energy becomes onboard kinetic energy in a falling situation may suit the mathematicians but it does not explain and actually detracts from what is really happening in energy terms.