Given,
The weight of the box, W=16 N
The height of the shelf, h=2.5 m
Potential energy is the energy possessed by an object due to its position. The gravitational potential energy is directly proportional to the height at which the object is situated.
The gravitational potential energy of the book is given by,
On substituting the known values,
Thus the gravitational potential energy of the book is 40 J