Law of conservation of energy (during a free fall )
Let a object be 'm' , lay on point 'a' and is lifted to pt 'h' and stopped at pt 'b'
therefore work done on the body is mgh.
as the body is at rest at 'b'
Kinetic energy at 'b' = 0
Potential energy at 'b' =mgh
Therefore total energy at 'b' =mgh +0
=mgh
the answer is really very long
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