The mechanical energy is defined as the sum of the potential energy and the kinetic energy, then we have:
[tex]E_{\text{mec}}=K+U[/tex]where K is the kinetic energy and U is the potential energy.
Plugging the values given for the mechanical and potential energy and solving for the kinetic energy we have that:
[tex]\begin{gathered} 100=K+60 \\ K=100-60 \\ K=40 \end{gathered}[/tex]Therefore 40 J are kinetic energy.
