A simple example of the transformation of kinetic energy into potential energy, and vice versa, is afforded by the pendulum.
Available kinetic energy is possessed by a system of two or more bodies in virtue of the relative motion of its parts.
If a body whose mass is m grammes be moving with a velocity of v centimetres per second relative to the earth, the available kinetic energy possessed by the system is Zmv 2 ergs if m be small relative to the earth.
Thus the estimation of kinetic energy is intimately affected by the choice of our base of measurement.
There is probably but little transformation of one form of kinetic energy into another in the plant.