When an object is lifted up it gains potential energy equal to $mgh$. When it is dropped from this height, gravity does work on it (which is also $mgh$) and this work is converted into the kinetic energy.
But what happens to the potential energy that it initially possessed when it was at a height? Shouldn't the object now have $mgh+\frac{1}{2} mv^2$ as the total energy ( previous potential energy + work done by gravity) ?
Best Answer
It is not the object that has the potential energy but the object and the Earth.
When the object is dropped the object/Earth system loses potential energy and the object and the Earth gain kinetic energy.
Because the mass of the Earth is so much greater than that of the object the Earth gains very little kinetic energy compared with the kinetic energy gained by the object.
So it is very common to read that the potential energy of the object is converted to the kinetic energy of the object.