Answer:
A mechanical computer uses moving parts to do it’s calculations. Think old style adding machines.Electronic computers use electronic oscillators to generate a clock. The oscillator might include a mechanical element such as a crystal, but the majority of the clock signal is processed in the electrical domain.
Explanation:
An example of a mechanical computer clock is a Swiss watch movement, which needs no electronics. Movement is based upon springs coupled to other mechanical pieces. Swiss watches are high precision mechanical computers that do counting. There are other types of more sophisticated mechanical computers. Research the works of Konrad Zuse and his Z1 mechanical computer.