aerodynamics studies the properties of moving air. on an airplane, this creates forces (lift and drag) and torques. Flight dynamics looks at what these forces do with your airplane (how does it move?). Also thrust and gravity are of course included with flight mechanics. They have nothing to do with aerodynamics.
actually they have EVERTHING to do with aerodynamics.. without thrust u cant generate lift, without gravity u cant provide unaided lift... but they ARE 2 sepearate fields.. and you are correct.. just wanted to clear that up a bit.