A heavy weight is dropped from a height of 1.2 m on a soda can, crushing it.

Is mechanical energy conserved in this process?

1. Yes (68/116) (59%)
2. No (48/116) (41%)

No. The potential energy decreases and the kinetic energy stays the same (zero before and after), so overall there's a loss of mechanical energy.

Is energy conserved in this process?

1. Yes
2. No

It had better be! If not we're breaking one of the fundamental laws of physics. The mechanical energy lost must have been transformed into other forms of energy (heat, sound, etc.). The total energy in the system should be the same.