It is true that the Mechanical energy is often changes between potential and Kinetic energy.
Step-by-step explanation:
Mechanical energy is the aggregate of potential energy and kinetic energy of an object. When the object is ''stationary'' or at ''rest'', potential energy will be maximum and kinetic energy will be zero.
When the object starts to move, potential energy decreases and kinetic energy increases from zero. As the distance moved by the object increases, potential energy reduces gradually.