What final electric test should always be performed on power tools especially those power tools with a metal case, like circular saws?

A leakage test

A current test

a motor resistance test

a line cord continuity test

I know that when an object is held at a particular height above the Earth, it has a quantity of potential energy associated with it, but no kinetic energy. When the object is dropped, it loses potential energy and gains kinetic energy, thereby ensuring that energy is conserved. However, I’ve never understood what happens when the object finally strikes the ground; at this point, it has no potential and no kinetic energy. I’m sure some of it is released as heat and sound, but that can’t account for all the energy, can it?

I also don’t know which sander to buy either. I’ll be using a compressor to run them.