Thank you John! I couldn't expect a better professional explanation. And if I could, suggest to anyone who doesn't want to know about disasters, such as flight 93, please ignore this thread and all my post.
There is a much better explanation for the engine distance, however, not tested yet. Once the plane nose dive to the ground with an angle (official version is that the plane dived from N.W. to S.E.). 757 has a very long fuselage from the wings to the nose. When nose dive, the front fuselage dived into ground absorbing kinetic energy, the tail would fly forward, due to the moment of inertia, I might be possible for the engine breaking away from the wing(which a deacceleration can be calculated by the strength of the wing, bots or anything fixed the engine to the wing, the wing to the plane) remember that the flight 93 was belley up before the dive. The broke away engine would have a speed much less than the impact speed (due to the break off), then tumble forward 300 yards. Such explanation would satisfy most people.
For jet engine, the fan is in the front of the engine, nose dive, the fan goes down first. How can it bounch and tumble 300 yards?
However my problem with this assumption is that the actuall crater at the crash site showed that the dive was from S.W. to the N.E.. The pictures government posted everywhere is upside down, i.e. North is down, South is up. Giving you a wrong impression that the plane did crash from N.W. to S.E. You can very easily veryfy this by looking at google map.
If this is the case, then the engine didn't tumble forward, but backward for 300 yards (PM said it was only a fan?). Why?