Mechanical energy is not conserved in bomb blasts due to the conversion of chemical potential energy into other forms of energy, such as thermal and kinetic energy. Before the blast, the energy is primarily stored as chemical potential energy in the explosive material. After the explosion, this energy transforms, resulting in a release of energy that causes shockwaves and fragmentation. The total mechanical energy, when accounting for all forms of energy, changes significantly during the blast. Therefore, while some mechanical energy may be present post-blast, it is not conserved in the traditional sense.