You move a 2.5 kg book from a shelf that is 1.2 m above the ground to a shelf that is 2.6 m above the ground. What is the change in potential energy of a system containing the book and Earth?
The change in potential energy of an object is given by [tex]U=mg \Delta h[/tex] where m is the mass of the object g is the gravitational acceleration [tex]\delta h[/tex] is the increase in altitude of the object
In our problem, [tex]m=2.5 kg[/tex] is the mass of the book, [tex]g=9.81 m/s^2[/tex] and [tex]\Delta h=2.6 m -1.2 m=1.4 m[/tex] is the increase in altitude of the book, so its variation of potential energy is [tex]U=mg\Delta h=(2.5 kg)(9.81 m/s^2)(1.4 m)=34.3 J[/tex]
