The kinetic energy of an object is defined as one half of the product of mass and velocity squared with the units kilograms meter squared per second squared. The kinetic energy of an object can be calculated using the momentum equation. The velocity term in the equation can be substituted from the momentum expression. Thereby, obtaining a relationship between momentum, mass, and kinetic energy of the object. The kinetic energy of an object depends on the frame of reference in which it is measured. For example, consider a person sitting in a car moving at a constant velocity. Since the person is stationary, his kinetic energy with respect to another stationary person sitting in the same car is zero. While, for an observer standing outside, it is non zero.