I have a point of curiosity that is related to this question. The Moon is face-locked to the Earth because any rotation energy that would exceed one turn per orbit around the Earth has been dissipated by tidal movements (right?). This is a result of its relatively close orbit for its size. The question is this: How much rotational energy would have to be added to the moon for it to turn around completely once per Earth year? That is, in one year, we would see the Moon turn completely once, seeing the far side.
Second, how long would it take for this added energy to be dissipated so that the Moon returned to its face-locked state? Thousands of years? Millions of years?
Third, how would this energy dissipation be manifested? Entirely as heat, as the oceans and crust of the earth, moving tidally, converted it to molecular motion? Or would any of it be manifest as a change, however slight, of the rotation speed of the earth? Would it make any difference if the Moon's added rotation was prograde or retrograde? (Viewed from the earth, the moon would turn right-to-left or left-to-right.)
This is, of course, not going to happen. I would assume any mass striking the moon hard enough and at the right angle to add this rotation would make quite a mess, and we would not be around long enough to enjoy the show. It's just an exercise for the curious mind, and I'm not learned enough to know how to begin.
