"The cow is strong." should be the preferred translation.
That would be a better translation for Η αγελάδα είναι δυνατή.
I was trying to find a way to remember this word--and of course it must be where 'dynamic' comes from.
Indeed there is a relation: 'dynamic' comes from Greek dynamikos "powerful," from dynamis "power".
The translation keep on changing between power/strength/force